tag:theconversation.com,2011:/au/topics/blue-light-9756/articlesBlue light – The Conversation2023-09-25T01:41:27Ztag:theconversation.com,2011:article/2131452023-09-25T01:41:27Z2023-09-25T01:41:27ZDo blue-light glasses really work? Can they reduce eye strain or help me sleep?<figure><img src="https://images.theconversation.com/files/549203/original/file-20230919-25-ucj5dq.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C1000%2C666&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/asian-womans-eyes-stress-blue-blocking-1391138681">Shutterstock</a></span></figcaption></figure><p>Blue-light glasses are said to <a href="https://www.baxterblue.com.au/collections/blue-light-glasses">reduce eye strain</a> when using <a href="https://www.blockbluelight.com.au/collections/computer-glasses">computers</a>, improve your <a href="https://www.ocushield.com/products/anti-blue-light-glasses">sleep</a> and protect your eye health. You can buy them yourself or your optometrist can prescribe them.</p>
<p>But <a href="https://mivision.com.au/2019/03/debate-continues-over-blue-blocking-lenses/">do they work</a>? Or could they do you harm?</p>
<p>We <a href="https://www.cochranelibrary.com/cdsr/doi/10.1002/14651858.CD013244.pub2/full">reviewed</a> the evidence. Here’s what we found.</p>
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Read more:
<a href="https://theconversation.com/health-check-will-i-damage-my-eyes-if-i-dont-wear-sunglasses-68582">Health Check: will I damage my eyes if I don't wear sunglasses?</a>
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<h2>What are they?</h2>
<p>Blue-light glasses, blue light-filtering lenses or blue-blocking lenses are different terms used to describe lenses that reduce the amount of short-wavelength visible (blue) light reaching the eyes. </p>
<p>Most of these lenses prescribed by an optometrist decrease blue light transmission by <a href="https://onlinelibrary.wiley.com/doi/10.1111/opo.12615">10-25%</a>. Standard (clear) lenses do not filter blue light.</p>
<p>A wide variety of lens products are available. A filter can be added to prescription or non-prescription lenses. They are widely marketed and are becoming <a href="https://onlinelibrary.wiley.com/doi/10.1111/opo.12615">increasingly popular</a>.</p>
<p>There’s often an added cost, which depends on the specific product. So, is the extra expense worth it?</p>
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Read more:
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<h2>Blue light is all around us</h2>
<p>Outdoors, sunlight is the main source of blue light. Indoors, light sources – such as light-emitting diodes (LEDs) and the screens of digital devices – emit varying degrees of blue light. </p>
<p>The amount of blue light emitted from artificial light sources is much lower than from the Sun. Nevertheless, artificial light sources are all around us, at home and at work, and we can spend a lot of our time inside.</p>
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<a href="https://images.theconversation.com/files/549210/original/file-20230920-16-tsb23b.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Blue light-filtering lenses block some blue light from screens from reaching the eye" src="https://images.theconversation.com/files/549210/original/file-20230920-16-tsb23b.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/549210/original/file-20230920-16-tsb23b.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/549210/original/file-20230920-16-tsb23b.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/549210/original/file-20230920-16-tsb23b.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/549210/original/file-20230920-16-tsb23b.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/549210/original/file-20230920-16-tsb23b.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/549210/original/file-20230920-16-tsb23b.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<span class="caption">Screens emit blue light. The lenses are designed to reduce the amount of blue light that reaches the eye.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-vector/blue-light-blocking-ray-filter-lens-2286229107">Shutterstock</a></span>
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<p>Our research team at the University of Melbourne, along with collaborators from Monash University and City, University London, sought to see if the best available evidence supports using blue light-filtering glasses, or if they could do you any harm. So we conducted a <a href="https://www.cochranelibrary.com/cdsr/doi/10.1002/14651858.CD013244.pub2/full">systematic review</a> to bring together and evaluate all the relevant studies. </p>
<p>We included all randomised controlled trials (clinical studies designed to test the effects of interventions) that evaluated blue light-filtering lenses in adults. We identified 17 eligible trials from six countries, involving a total of 619 adults.</p>
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Read more:
<a href="https://theconversation.com/does-my-treatment-work-how-major-medical-reviews-can-be-gold-standard-evidence-yet-flawed-205014">Does my treatment work? How major medical reviews can be 'gold standard' evidence, yet flawed</a>
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<h2>Do they reduce eye strain?</h2>
<p>We found no benefit of using blue light-filtering lenses, over standard (clear) lenses, to reduce eye strain with computer use. </p>
<p>This conclusion was based on consistent findings from three studies that evaluated effects on eye strain over time periods ranging from two hours to five days.</p>
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Read more:
<a href="https://theconversation.com/screentime-can-make-you-feel-sick-here-are-ways-to-manage-cybersickness-163851">Screentime can make you feel sick – here are ways to manage cybersickness</a>
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<h2>Do they help you sleep?</h2>
<p>Possible effects on sleep were uncertain. Six studies evaluated whether wearing blue-light filtering lenses before bedtime could improve sleep quality, and the findings were mixed. </p>
<p>These studies involved people with a diverse range of medical conditions, including insomnia and bipolar disorder. Healthy adults were not included in the studies. So we do not yet know whether these lenses affect sleep quality in the general population.</p>
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Read more:
<a href="https://theconversation.com/booting-up-or-powering-down-how-e-readers-affect-your-sleep-36145">Booting up or powering down: how e-readers affect your sleep</a>
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<h2>Do they boost your eye health?</h2>
<p>We did not find any clinical evidence to support using blue-light filtering lenses to protect the macula (the region of the retina that controls high-detailed, central vision). </p>
<p>None of the studies evaluated this.</p>
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Read more:
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<h2>Could they do harm? How about causing headaches?</h2>
<p>We could not draw clear conclusions on whether there might be harms from wearing blue light-filtering lenses, compared with standard (non blue-light filtering) lenses. </p>
<p>Some studies described how study participants had headaches, lowered mood and discomfort from wearing the glasses. However, people using glasses with standard lenses reported similar effects.</p>
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Read more:
<a href="https://theconversation.com/health-check-what-causes-headaches-42254">Health Check: what causes headaches?</a>
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<h2>What about other benefits or harms?</h2>
<p>There are some important general considerations when interpreting our findings. </p>
<p>First, most of the studies were for a relatively short period of time, which limited our ability to consider longer-term effects on vision, sleep quality and eye health. </p>
<p>Second, the review evaluated effects in adults. We don’t yet know if the effects are different for children.</p>
<p>Finally, we could not draw conclusions about the possible effects of blue light-filtering lenses on many vision and eye health measures, including colour vision, as the studies did not evaluate these.</p>
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Read more:
<a href="https://theconversation.com/curious-kids-why-are-people-colour-blind-107599">Curious Kids: why are people colour blind?</a>
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<h2>In a nutshell</h2>
<p>Overall, based on relatively limited published clinical data, our review does not support using blue-light filtering lenses to reduce eye strain with digital device use. It is unclear whether these lenses affect vision quality or sleep, and no conclusions can be drawn about any potential effects on the health of the retina. </p>
<p>High-quality research is needed to answer these questions, as well as whether the effectiveness and safety of these lenses varies in people of different ages and health status.</p>
<p>If you have eye strain, or other eye or vision concerns, discuss this with your optometrist. They can perform a thorough examination of your eye health and vision, and discuss any relevant treatment options.</p><img src="https://counter.theconversation.com/content/213145/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>In the past three years, Laura Downie's research laboratory at the University of Melbourne has received funding from Alcon Laboratories, Azura Ophthalmics, CooperVision and Novartis for clinical research studies unrelated to this article. She is affiliated with the Tear Film and Ocular Surface Society, as a global ambassador.</span></em></p>They’re heavily promoted. Your optometrist may even prescribe them. But when we looked at the evidence, this is what we found.Laura Downie, Associate Professor in Optometry and Vision Sciences, The University of MelbourneLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1786012022-07-01T12:18:27Z2022-07-01T12:18:27ZYour body has an internal clock that dictates when you eat, sleep and might have a heart attack – all based on time of day<figure><img src="https://images.theconversation.com/files/471709/original/file-20220629-26-g88r2h.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C2121%2C1412&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Syncing your circadian rhythm to a natural light-dark cycle could improve your health and well-being.</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/the-circadian-rhythms-are-controlled-by-circadian-royalty-free-image/1361759855">nambitomo/iStock via Getty Images Plus</a></span></figcaption></figure><p>Anyone who has suffered from jet lag or struggled after turning the clock forward or back an hour for daylight saving time knows all about what researchers call your <a href="https://doi.org/10.1126/science.aah4965">biological clock</a>, or circadian rhythm – the “master pacemaker” that synchronizes how your body responds to the passing of one day to the next. </p>
<p>This “clock” is made up of about <a href="https://doi.org/10.1038/nature00965">20,000 neurons</a> in the <a href="https://my.clevelandclinic.org/health/articles/22566-hypothalamus">hypothalamus</a>, the area near the center of the brain that coordinates your body’s unconscious functions, like breathing and blood pressure. Humans aren’t the only beings that have an internal clock system: All vertebrates – or mammals, birds, reptiles, amphibians and fish – have biological clocks, as do plants, fungi and bacteria. Biological clocks are why cats are most active at dawn and dusk, and why flowers bloom at certain times of day.</p>
<p>Circadian rhythms are also essential to health and well-being. They govern your body’s physical, mental and behavioral changes over each 24-hour cycle in response to environmental cues like light and food. They’re why more <a href="https://doi.org/10.1172/jci80590">heart attacks and strokes</a> occur early in the morning. They’re also why mice that are <a href="https://doi.org/10.1101%2Fgad.1432206">missing their biological clocks</a> age faster and have shorter lifespans, and people with a <a href="https://doi.org/10.1016/j.cell.2017.03.027">mutation in their circadian clock genes</a> have abnormal sleep patterns. Chronic misalignment of your circadian rhythm with external cues, as seen in <a href="https://doi.org/10.1038/nrn3743">night-shift workers</a>, can lead to a wide range of physical and mental disorders, including obesity, Type 2 diabetes, cancer and cardiovascular diseases. </p>
<p>In short, there is ample evidence that your biological clock is critical to your health. And <a href="https://scholar.google.com/citations?user=3id8z2UAAAAJ&hl=ja">chronobiologists like me</a> are studying how the day-night cycle affects your body to better understand how you can modify your behaviors to use your internal clock to your advantage.</p>
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<figcaption><span class="caption">Your body has an internal clock that helps keep it in working order.</span></figcaption>
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<h2>How biological rhythms affect your health</h2>
<p>Your biological clock affects your health by regulating your sleep-wake cycles and fluctuations in blood pressure and body temperature. It does this primarily by syncing your endocrine system to environmental light-dark cycles so that certain hormones are released in certain amounts at certain times of day. </p>
<p>The pineal grand in your brain, for example, produces <a href="https://www.nccih.nih.gov/health/melatonin-what-you-need-to-know">melatonin</a>, a hormone that helps regulate sleep in response to darkness. Doctors advise reducing exposure to artificial blue light from electronic devices before bedtime because it can disrupt melatonin secretion and sleep quality.</p>
<p>Your circadian rhythm also affects your metabolism. Among other things, sleep helps you regulate <a href="https://doi.org/10.1371/journal.pmed.0010062">leptin</a>, a hormone that controls appetite. Your leptin levels fluctuate throughout the day according to a rhythm set by your circadian clock. Insufficient or irregular sleep can <a href="https://doi.org/10.1016/j.cmet.2015.06.005">disrupt leptin production</a>, which can make us hungrier and lead to weight gain.</p>
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<a href="https://images.theconversation.com/files/471958/original/file-20220630-12-3qhivk.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Chart showing cortisol and melatonin levels fluctuating over the course of the day, with cortisol levels peaking at around 6 AM and melatonin peaking at around midnight" src="https://images.theconversation.com/files/471958/original/file-20220630-12-3qhivk.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/471958/original/file-20220630-12-3qhivk.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=555&fit=crop&dpr=1 600w, https://images.theconversation.com/files/471958/original/file-20220630-12-3qhivk.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=555&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/471958/original/file-20220630-12-3qhivk.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=555&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/471958/original/file-20220630-12-3qhivk.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=698&fit=crop&dpr=1 754w, https://images.theconversation.com/files/471958/original/file-20220630-12-3qhivk.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=698&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/471958/original/file-20220630-12-3qhivk.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=698&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<span class="caption">Your hormones fluctuate rhythmically over the course of the day. The stress hormone cortisol typically peaks in the morning, while the sleep hormone melatonin typically peaks in the night.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/illustration/sleep-wake-cycle-royalty-free-illustration/1398204621">Pikovit44/iStock via Getty Images Plus</a></span>
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<p>In recent years, researchers have discovered even more ways your circadian clock can affect your health. For example, there is now research suggesting that eating at set times of day, or <a href="https://doi.org/10.1016/j.cmet.2012.04.019">time-restricted feeding</a>, can prevent obesity and metabolic diseases. <a href="https://doi.org/10.1007/978-3-030-81147-1_3">Depression and other mood disorders</a> may also be linked to dysfunctional circadian control that lead to changes in how your genes are expressed.</p>
<p>The time of day when you <a href="https://doi.org/10.1016/j.cmet.2019.06.019">take your medicine</a> can also affect how well it works and how severe any side effects might be. Likewise, your biological clock is a <a href="https://doi.org/10.1056/NEJMra1802337">potential target</a> for <a href="https://doi.org/10.1038/nature25170">cancer chemotherapies</a> and anti-obesity treatments. </p>
<p>And finally, even your <a href="https://www.nature.com/articles/s41467-018-08259-7">personality</a> might be shaped by whether your internal clock make you a “morning person” or a “night person.”</p>
<h2>Getting the most out of exercise</h2>
<p>Circadian clocks also provide a potential answer to when is the best time of day to maximize the benefits of physical exercise.</p>
<p>To study this, my colleagues and I collected blood and tissue samples from the brains, hearts, muscles, livers and fat of mice that exercised either before breakfast in the early morning or after dinner in the late evening. We used a tool called a mass spectrometer to detect approximately 600 to 900 molecules each organ produced. These metabolites served as real-time snapshots of how the mice responded to exercise at specific times of day.</p>
<p>We stitched these snapshots together to create a map of how exercise in the morning versus evening affected each of the mice’s different organ systems – what we called an <a href="https://doi.org/10.1016/j.cmet.2021.12.016">atlas of exercise metabolism</a>. </p>
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<span class="caption">The best time of day to exercise might be the time when you feel you perform best.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/silhouette-man-run-on-beach-with-sunrise-and-sea-royalty-free-image/1359952356">Anuruk Charoenamornrat/EyeEm via Getty Images</a></span>
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<p>Using this atlas, we saw that time of day affects how each organ uses energy during exercise. For instance, we found that early morning exercise reduced blood glucose levels more than late evening exercise. Exercise in the late evening, however, allowed the mice to benefit from energy they stored from their meals and increased their endurance.</p>
<p>Of course, mice and humans have many differences along with their similarities. For one, mice are more active at night than during the day. Still, we believe that our findings could help researchers better understand how exercise affects your health and, if timed appropriately, can be optimized based on time of day to meet your personal health goals.</p>
<h2>Getting along with your biological clock</h2>
<p>I believe that the field of chronobiology is growing, and we will produce even more research providing practical applications and insights into health and well-being in the future. </p>
<p>In <a href="https://www.bio.tamu.edu/faculty-page-shogo-sato/">my own work</a>, for example, a better understanding of how exercising at different times of day affects your body could help tailor exercise plans to maximize specific benefits for patients with obesity, Type 2 diabetes and other diseases. </p>
<p>There is still much to learn about how your circadian clock works. But in the meantime, there are some tried and true ways people can synchronize their internal clocks for better health. These include regular exposure to sunlight to trigger the endocrine system to produce vitamin D, staying active during the day so you fall asleep more easily at night and avoiding caffeine and reducing your exposure to artificial light before bedtime.</p><img src="https://counter.theconversation.com/content/178601/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Shogo Sato receives funding from the Brain & Behavioral Research Foundation (NARSAD Young Investigator Grant, 28681) and start-up funds from Texas A&M University. </span></em></p>Your body follows a circadian rhythm that influences everything from how well your medications work to the best time for exercise.Shogo Sato, Assistant Professor of Biology, Texas A&M UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1858192022-07-01T10:39:43Z2022-07-01T10:39:43ZHow reindeer eyes transform in winter to give them twilight vision<figure><img src="https://images.theconversation.com/files/471635/original/file-20220629-26-u3m5bs.jpg?ixlib=rb-1.1.0&rect=30%2C6%2C3995%2C1907&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/reindeer-photo-people-northern-mongolia-1542831665">Shutterstock</a></span></figcaption></figure><p>Reindeer are loved the world over for their dark, expressive eyes, majestic antlers and magical association with Santa Claus. The moment you learn the cold, hard truth of how Christmas presents arrive under the tree is a harrowing one that blights many a childhood. But reindeer are more special than your cynical older sibling or classmates would have had you believe. </p>
<p>The Arctic reindeer, like its main predator the wolf, is incredibly well adapted to its snowy home, where winter conditions can see temperatures drop to -50°C and low levels of daylight. Reindeer have a second layer of fur, and wide crescent-shaped hooves that keep them stable and allow them to dig in the snow. And as <a href="http://rspb.royalsocietypublishing.org/lookup/doi/10.1098/rspb.2022.1002">our new study </a> shows, their eyes undergo physical change as the seasons turn which allows them to see clearly in the long winter twilight. </p>
<p>Mid-winter in the Arctic is either dark or twilight, when the sun is below the horizon, all day. Reindeer need to find and uncover their winter food, lichen, by brushing the snow-covered ground with their hooves, antlers and muzzles. Lichens are plentiful in the Arctic – an ideal food source that reindeer can find wherever they go. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/471600/original/file-20220629-24-rua34s.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/471600/original/file-20220629-24-rua34s.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=397&fit=crop&dpr=1 600w, https://images.theconversation.com/files/471600/original/file-20220629-24-rua34s.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=397&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/471600/original/file-20220629-24-rua34s.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=397&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/471600/original/file-20220629-24-rua34s.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=499&fit=crop&dpr=1 754w, https://images.theconversation.com/files/471600/original/file-20220629-24-rua34s.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=499&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/471600/original/file-20220629-24-rua34s.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=499&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Northern lichen.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure>
<h2>Twilight is special</h2>
<p>Reindeer feed in twilight when wolves hunt. However, twilight has a unique property which distinguishes it from day or night: it is extremely blue, containing very little green, yellow and orange. </p>
<p>This is because, lit by a sun below the horizon, the Earth’s ozone layer acts as a filter spanning the sky, which in twilight absorbs almost all light except blue light. The sunlight travels a greater distance through the atmosphere, passing horizontally through the ozone layer. This ozone-blue is different from the <a href="https://spaceplace.nasa.gov/blue-sky/en/#:%7E:text=Sunlight%20reaches%20Earth's%20atmosphere%20and,sky%20most%20of%20the%20time.">clear daytime sky-blue </a>, which is caused by scattering of sunlight by air molecules. </p>
<p>Although artists call this time after sunset “<a href="https://en.wikipedia.org/wiki/Blue_hour_">the blue hour</a>” we tend not to notice it because our eyes adapt to the slowly changing colour. As darkness approaches, our vision switches from relying on the <a href="https://www.cis.rit.edu/people/faculty/montag/vandplite/pages/chap_9/ch9p1.html">cone receptors</a> that give us colour vision to using the more sensitive rods, which are colour blind. In winter, the twilight can last more than a third of the day in <a href="https://en.wikipedia.org/wiki/Polar_night_">polar habitats</a>. </p>
<p><a href="https://nywolf.org/2020/05/why-do-wolves-eyes-glow-in-the-dark-4/#:%7E:text=Wolves%20have%20a%20special%20layer,reflected%20back%20into%20the%20eye.">Wolves</a> and reindeer both improve their sensitivity to Arctic twilight with a “mirror” behind the retina. When light enters the eye and passes through the retina, not all of it is detected and absorbed by specialised neurons called <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4712787/#:%7E:text=Rod%20and%20cone%20photoreceptors%20are,for%20the%20survival%20of%20photoreceptors">photoreceptors</a>. The mirror instead reflects it back through the retina for a second time, when more light will be detected. The reindeer see an image that is brighter but slightly fuzzier because the mirror scatters some light sideways, a bit like a misted glass. </p>
<p>This is an advantage in dim light because the animal relies more on visual contrast and motion than visual sharpness. The mirror, called the <em><a href="https://pubmed.ncbi.nlm.nih.gov/14738502/#:%7E:text=The%20tapetum%20lucidum%20is%20a,sensitivity%20at%20low%20light%20levels.">tapetum lucidum</a></em> (shining carpet), evolved independently in many animals. Important exceptions include humans and raptors, who need crisp images. </p>
<h2>Eyes that change with the seasons</h2>
<p>Our study <a href="https://royalsocietypublishing.org/doi/10.1098/rspb.2022.1002">compared the eyes of reindeer</a> that died during summer to specimens from reindeer that died in the winter. </p>
<p>It showed that reindeer eyes undergo a unique seasonal change in its tapetum and change colour, reflecting gold-turquoise light in the summer and mirroring deep <a href="https://royalsocietypublishing.org/doi/10.1098/rspb.2013.2451">blue in the winter</a>. Both lichen and wolf fur reflect less blue than other colours so appear dark against the snow-covered landscape. </p>
<figure class="align-center ">
<img alt="Reindeer walks across snowy ground" src="https://images.theconversation.com/files/471637/original/file-20220629-19-2imvze.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/471637/original/file-20220629-19-2imvze.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/471637/original/file-20220629-19-2imvze.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/471637/original/file-20220629-19-2imvze.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/471637/original/file-20220629-19-2imvze.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/471637/original/file-20220629-19-2imvze.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/471637/original/file-20220629-19-2imvze.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Reindeer eyes change colour with the seasons.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/portrait-reindeer-massive-antlers-pulling-sleigh-1385226686">Shutterstock</a></span>
</figcaption>
</figure>
<p>A reindeer’s tapetum uses the same structure that makes the <a href="http://archive.boston.com/bostonglobe/ideas/brainiac/2014/07/if_you_go_looki.html#:%7E:text=A%20peacock's%20tail%20feathers%2C%20for,disc%20have%20the%20same%20effect">peacock’s</a> iridescent feathers, the Morpho butterfly’s brilliant blue wings and the opal gem’s flashes of colour. This is called <a href="https://pubs.rsc.org/en/content/articlelanding/2013/ra/c3ra41096j#:%7E:text=Structural%20color%20is%20a%20special,grating%2C%20scattering%20and%20photonic%20crystals.">structural colouration</a>. </p>
<p>In the reindeer tapetum, these structures are very fine fibres of collagen too small to be seen with a light microscope, similar to but finer than the structure of muscles. Imagine these fibres as a large number of pencils neatly stacked in a transparent box in a hexagonal pattern. </p>
<p>Let in enough water to fill the gaps, reduce the scale by a factor of about 40,000 and the box will reflect blue light. This represents the winter tapetum. To transform to the summer tapetum, increase amount of water tenfold and double the depth of the box. At this tiny scale, the fibres will roughly maintain their hexagonal pattern, but there will be more gaps between them.</p>
<p>We think this transformation is triggered by <a href="https://royalsocietypublishing.org/doi/10.1098/rspb.2013.2451">a pressure</a> change in the reindeer eye that happens in summer and winter.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/471838/original/file-20220630-12-k1r0mg.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/471838/original/file-20220630-12-k1r0mg.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=399&fit=crop&dpr=1 600w, https://images.theconversation.com/files/471838/original/file-20220630-12-k1r0mg.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=399&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/471838/original/file-20220630-12-k1r0mg.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=399&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/471838/original/file-20220630-12-k1r0mg.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=502&fit=crop&dpr=1 754w, https://images.theconversation.com/files/471838/original/file-20220630-12-k1r0mg.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=502&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/471838/original/file-20220630-12-k1r0mg.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=502&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Wolves are the main reindeer predator.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/portrait-wolf-eurasian-known-gray-grey-1609843993">Shutterstock</a></span>
</figcaption>
</figure>
<p>Another way to think of it is as reindeer eyes having summer and winter tyres. During very cold conditions, you let some air out of the tyres to increase traction on the ice. The reindeer lets fluid out of its tapetum to reveal a better view of its surroundings.</p>
<p>This finding may help engineers to make products that change reflected colour. The opportunities are endless. If you use a surface coated with a reflecting nano-
structure, similar to that of the reindeer’s tapetum, rather than a pigment-based paint, you can change colour by changing the separation of the scaled-down “pencils” that reflect the light. For example, you could change the colour of your car by tuning the separation. Unlike many pigments, these structural paints do not fade over time. </p>
<p>So while reindeer have long inspired Christmas tradition told all over the world, now they could inspire technology and science.</p><img src="https://counter.theconversation.com/content/185819/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Robert A E Fosbury receives funding from BBSRC, The project was originally funded by BB/F008244/1</span></em></p>There’s more to reindeer than meets the eye.Robert A E Fosbury, Honorary professor, UCL Institute of Ophthalmology, UCLLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1850742022-06-20T09:37:18Z2022-06-20T09:37:18ZBlue light: what we do and don’t know about the damage it causes our skin<figure><img src="https://images.theconversation.com/files/469485/original/file-20220617-25-ma9rqf.jpg?ixlib=rb-1.1.0&rect=44%2C44%2C5946%2C3943&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Is blue light harmful?</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/disappointed-sad-woman-holding-mobile-phone-1129353881">Shutterstock</a></span></figcaption></figure><p>Take a wander down the skincare aisle of any health and beauty retailer and you’ll be met with a bewildering array of creams and sprays, promising to protect you from various threats to your skin.</p>
<p>You might have noticed skincare companies claiming their products can protect you from the effects of blue light. If you hadn’t thought about blue light before, you’d be forgiven for worrying about whether you should be concerned. </p>
<p>First you need to understand what blue light is. </p>
<p>Visible light accounts for 50% of the sunlight spectrum and, as the name suggests, it’s the only part of light that can be detected by the human eye. The blue band of this visible spectrum has a particularly high energy level.</p>
<p>The longer the wavelength, the less energy it transmits. Blue light has very short, high energy waves.</p>
<p>Blue light is all around you. The sun emits blue light. So do fluorescent and incandescent light bulbs, mobile phones, computer screens and flat screen televisions. </p>
<h2>What are the risks?</h2>
<p>There is mounting evidence that blue light can have a harmful effect on the skin and eyes and disrupt the circadian rhythm (your internal clock). Typically, studies investigating the impact of sun radiation on the skin have focused on ultraviolet radiation, particularly UVB, which is responsible for sunburn. The most frequently reported effect of blue light exposure is a <a href="https://pubmed.ncbi.nlm.nih.gov/26977040/">significant increase in reactive oxygen species (ROS)</a>, highly reactive chemicals formed from oxygen. Too much ROS can <a href="https://pubmed.ncbi.nlm.nih.gov/15797866/">damage your DNA</a> and <a href="https://aacrjournals.org/mcr/article/14/7/612/89680/Oxidative-Stress-Induced-Protein-Damage-Inhibits">key enzymes such as those responsible for DNA repair</a>, increasing your risk of cancer. </p>
<p><a href="https://www.sciencedirect.com/science/article/pii/S1011134421002517">Our research</a> showed blue light can induce pigmentation (tanning) across skin types. While many people consider a deep tan a desirable trait, it is a marker of skin damage and ROS. Others researchers found skin tans from visible light (which includes blue light) had <a href="https://www.sciencedirect.com/science/article/pii/S0022202X15349307">darker pigmentation that lasted longer</a> compared to ultraviolet radiation exposure. Our studies also showed blue light can <a href="https://www.nature.com/articles/s41598-018-30738-6">activate genes associated with inflammation and photoageing</a> (skin damge). Several studies have proved typical sunscreens do not prevent <a href="https://www.sciencedirect.com/science/article/pii/S1011134421002517">blue</a> and <a href="https://pubmed.ncbi.nlm.nih.gov/26977040/">visible</a> light damage. </p>
<p>While blue light appears to be less potent than ultraviolet radiation, this may be accounted for by the relatively larger amounts of blue light that reach the Earth. UVR accounts for around 5% of solar radiation in the UK at midday in the summer. Blue light makes up around <a href="https://onlinelibrary.wiley.com/doi/10.1111/php.12422">three times more at 15%</a>.</p>
<p><a href="https://onlinelibrary.wiley.com/doi/10.1111/jocd.13837">There are some beneficial effects</a> of blue light. It has been used to treat skin conditions including <a href="https://www.karger.com/Article/FullText/448000">eczema</a>, it is widely used in <a href="https://journals.lww.com/jdnaonline/Fulltext/2015/05000/Current_Evidence_and_Applications_of_Photodynamic.4.aspx">photodynamic therapy</a>, which is used to treat a range of skins conditions, from acne to cancer, and it boosts <a href="https://pubmed.ncbi.nlm.nih.gov/22081819/">wound healing</a>. But the harmful effects of blue light are likely to outweigh the positives for healthy people.</p>
<figure class="align-center ">
<img alt="Man in bed looks at laptop" src="https://images.theconversation.com/files/469486/original/file-20220617-17-pypzma.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/469486/original/file-20220617-17-pypzma.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/469486/original/file-20220617-17-pypzma.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/469486/original/file-20220617-17-pypzma.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/469486/original/file-20220617-17-pypzma.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/469486/original/file-20220617-17-pypzma.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/469486/original/file-20220617-17-pypzma.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">We are all exposed to more blue light than ever before.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/man-home-front-laptop-watching-movies-1662226270">Shutterstock</a></span>
</figcaption>
</figure>
<p>Blue light can damage the skin but it’s less clear which sources of blue light are harmful to humans. The blue light from screens is responsible for a fraction of the blue light doses we get. <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6280109/pdf/JBPE-8-447.pdf">Research</a> has shown screens from devices can increase ROS production. However, a <a href="https://www.beiersdorf.com/newsroom/press-releases/all-press-releases/2021/05/04-cell-phone-screens-do-not-damage-skin#:%7E:text=Artificial%20blue%20light%20has%20negligible,knowledge%20and%20of%20scientific%20studies.">study</a> by German skincare manufacturer Biersdorf found that an entire week’s worth exposure to blue light from a screen at a distance of 30cm is equivalent to just one minute of midday summer sun in Hamburg, Germany. <a href="https://www.sciencedirect.com/science/article/pii/S0190962219333249?via%3Dihub">Another study</a> found blue light from screens were 100 - 1,000 times less intense than blue light from the sun. It also failed to trigger melasma, which causes patches of skin discolouration, in patients who have the condition. It’s true we are spending more time in front of screens than ever before but while screens may cause some damage, it’s insignificant compared with sun exposure. </p>
<h2>Blue light skincare</h2>
<p>The cosmetics industry has started developing a wide range of skincare products that brands claim prevent blue light damage. However, there is <a href="https://onlinelibrary.wiley.com/doi/10.1111/jocd.13854">no regulated or standardised test</a> to assess a product’s ability to prevent blue light damage. Companies do carry out scientific tests on these products. But they can use any number of assessments in their work. This is very different from the regulations around sunscreen that claim to contain <a href="https://www.iso.org/standard/72250.html">Sun protection factor (SPF).</a>. SPF testing is closely regulated by the International Organization for Standardization (ISO). All products that claim to contain an SPF undergo an identical testing regime.</p>
<p>The lack of regulation for blue light claims makes it impossible for consumers to make informed choices about the level of protection offered and differences between products. This lack of regulation is unlikely to be dangerous for consumers, but the benefit from the products may be limited. Given the evidence around blue light emitted by screens, it’s worth applying scepticism to any claims that a product is needed to prevent damage from your computer screen or phone.</p>
<p>Traditional photoprotection products (such as sunscreens) don’t typically protect you from blue light damage. It’s encouraging the skincare industry is trying to address this need. But it is crucial that governments take the next step in the process and develop industry-wide, standardised testing. In the meantime, it is important to remember to limit any exposure to the sun. The use of sunscreens (or any product containing an SPF rating) have been proven to prevent skin cancer and photoageing, and products advertising blue light protection may give an additional benefit.</p><img src="https://counter.theconversation.com/content/185074/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Karl Lawrence has previously received funding from the sunscreen industry.</span></em></p>What you need to know about blue light protection lotions.Karl Lawrence, Post Doctoral Researcher, Photobiology, King's College LondonLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1701082021-11-01T02:27:07Z2021-11-01T02:27:07ZLED face masks are popular on social media for glowing skin – but they could disrupt your sleep<figure><img src="https://images.theconversation.com/files/429513/original/file-20211101-23-k9xukq.jpg?ixlib=rb-1.1.0&rect=42%2C42%2C4681%2C3109&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/woman-led-light-therapy-facial-beauty-1506384749">Shutterstock</a></span></figcaption></figure><p>LED face masks are the latest device promoted on social media as a marriage of technology and beauty. </p>
<p>A range of celebrities have endorsed portable versions of the product that was previously offered in beauty salons. Actress Olivia Munn <a href="https://www.usmagazine.com/stylish/pictures/celebrities-who-use-led-light-therapy-at-home-treatment-benefits/olivia-munn-19/">carries hers with her at all times</a>. Julia Roberts, Victoria Beckham and Chrissy Tiegen are also <a href="https://www.harpersbazaar.com/uk/beauty/skincare/a31908990/celebrity-led-mask/">reportedly</a> fans. The trend has even achieved the social media holy grail – a Kardashian Instagram <a href="https://www.instagram.com/p/BCemzbnk1qQ/?taken-by=kourtneykardash&hl=en%22">post</a>. </p>
<p>But regardless of whether they’ll help make your skin glow, our understanding of circadian rhythms suggests they have the potential to disrupt users’ sleep-wake cycles.</p>
<p><div data-react-class="InstagramEmbed" data-react-props="{"url":"https://twitter.com/TheCut/status/1445116733170278403","accessToken":"127105130696839|b4b75090c9688d81dfd245afe6052f20"}"></div></p>
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<strong>
Read more:
<a href="https://theconversation.com/6-ways-to-stop-daylight-saving-derailing-your-childs-sleep-123871">6 ways to stop daylight saving derailing your child’s sleep</a>
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</em>
</p>
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<h2>Daily rhythms</h2>
<p>The human body has its own internal clock which, among other things, helps to control our sleep-wake patterns. This internal clock is influenced by several factors, the most potent being light exposure directly into the eyes. More specifically, short-wavelength “blue light” <a href="https://journals.sagepub.com/doi/10.1177/0748730415585413">influences this system the most</a>. </p>
<p>Exposure to this type of light at night has been shown <a href="https://onlinelibrary.wiley.com/doi/abs/10.1111/jpi.12562">interrupt the production of melatonin</a> – also known as “the sleep hormone”. <a href="https://www.psychiatrictimes.com/view/role-melatonin-circadian-rhythm-sleep-wake-cycle">Melatonin</a> is produced by the pineal gland in the brain and released within 2 hours of your habitual bedtime – preparing the body for sleep. But bright blue light exposure may interrupt this process. </p>
<p>There are a range of sources for blue light – including our beloved phones, electronic devices and also the room lighting in our homes. While it has become a common recommendation to avoid using electronic devices close to bedtime, in the context of blue light exposure, our phones and tablets <a href="https://winksleep.online/blog/65-blue-screenlight-making-it-harder-to-fall-asleep-is-the-number-1-sleep-myth-of-our-time">do not seem to be bright enough to impact sleep</a>. In fact, home lighting appears to have a greater influence – likely due to the <a href="https://sleepjunkies.com/home-lighting-circadian-rhythms/">transition to energy-efficient LED, “blue light” wavelength light</a>.</p>
<p>Last year, Monash University researchers examined sleep and light exposure in 57 participants, finding that <a href="https://www.nature.com/articles/s41598-020-75622-4#Sec7">nearly half of them had LED lighting that suppressed melatonin by 50%</a>. The study also found those with greater evening light exposure had increased wakefulness after bedtime. </p>
<p>Insufficient sleep has been shown to increase the likelihood of poor health outcomes, including <a href="https://academic.oup.com/eurheartj/article/32/12/1484/502022">cardiovascular disease</a>.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/427973/original/file-20211022-23-1twj2py.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="woman with phone in bed" src="https://images.theconversation.com/files/427973/original/file-20211022-23-1twj2py.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/427973/original/file-20211022-23-1twj2py.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/427973/original/file-20211022-23-1twj2py.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/427973/original/file-20211022-23-1twj2py.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/427973/original/file-20211022-23-1twj2py.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/427973/original/file-20211022-23-1twj2py.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/427973/original/file-20211022-23-1twj2py.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Room LED lighting may be a bigger issue than phones and devices when it comes to sleep disruption.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/closeup-asian-women-using-smartphone-late-1746438284">Shutterstock</a></span>
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</figure>
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<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/poor-sleep-is-really-bad-for-your-health-but-we-found-exercise-can-offset-some-of-these-harms-163270">Poor sleep is really bad for your health. But we found exercise can offset some of these harms</a>
</strong>
</em>
</p>
<hr>
<h2>How face masks compare to other LED sources</h2>
<p>LED mask manufacturers say they are <a href="https://www.marieclaire.com/beauty/g32894063/led-light-therapy-masks/">the “future of skin care”</a>, with masks emitting light at different wavelengths to target particular skin-related outcomes. </p>
<p>Several devices are FDA-approved in the United States, and claim to <a href="https://www.violetgrey.com/product/led-mask/DG-BA568110?utm_source=pepperjam&utm_medium=affiliate&utm_campaign=21181&clickId=3730626806">target acne with “blue light” modes</a> – the precise wavelength range that may impact melatonin production. </p>
<p>To date, no experimental research studies have examined the impact of these devices, and their blue light settings, on sleep or the human body clock. But given the device’s proximity to users’ eyes and the intensity of LED light bulbs, it is reasonable to flag concerns about their possible impact on our body clock. </p>
<p><a href="https://lens.monash.edu/@sean-cain">Sean Cain</a>, a leading scientist on the impact of light exposure on human health, coined an analogy to provide perspective to the sources of artificial light. The light we receive from electronic devices can be thought of as like a glass of water being poured over your head, while home LED lighting is more like a bucket of water. In keeping with this analogy, could LED masks be something on the scale of a bathtub or swimming pool? Further research could quantify their effect. </p>
<p><div data-react-class="InstagramEmbed" data-react-props="{"url":"https://www.instagram.com/p/BCemzbnk1qQ/?taken-by=kourtneykardash\u0026hl=en","accessToken":"127105130696839|b4b75090c9688d81dfd245afe6052f20"}"></div></p>
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<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/snooze-blues-how-using-your-favourite-song-as-an-alarm-can-help-you-wake-up-more-alert-158233">Snooze blues? How using your favourite song as an alarm can help you wake up more alert</a>
</strong>
</em>
</p>
<hr>
<h2>You can still make like a Kardashian … in the daytime</h2>
<p>These concerns, based on well-established circadian principles, do not rule out the use of these devices entirely. However, it is important for people who use them to avoid doing so at night – especially on the blue light settings. </p>
<p>Ideally, use of the masks should be during daylight hours, to avoid potential sleep disturbances and/or shifts in the human body clock. Future research could clarify any negative outcomes associated with these devices and potentially prompt manufacturers to provide recommendations on the timing of their use.</p><img src="https://counter.theconversation.com/content/170108/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Dean J. Miller's position at CQUniversity is funded by WHOOP inc . </span></em></p>LED face masks are popular with celebrities and promise a glowing complexion. But should they come with ‘daytime use’ recommendation?Dean J. Miller, Research Officer, CQUniversity AustraliaLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1638512021-07-22T12:27:39Z2021-07-22T12:27:39ZScreentime can make you feel sick – here are ways to manage cybersickness<figure><img src="https://images.theconversation.com/files/411955/original/file-20210719-15-1jltvrb.jpg?ixlib=rb-1.1.0&rect=11%2C5%2C3982%2C3988&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Your devices can trigger symptoms similar to motion sickness.</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/illustration/man-and-modern-technology-communication-royalty-free-illustration/1063800132">Bakal/Stock via Getty Images Plus</a></span></figcaption></figure><p>Do you ever feel like the light of your computer screen is burrowing into your eyes and making your head pulse? Or feel dizzy or nauseous after looking at your phone? While you might think these sensations are just <a href="https://doi.org/10.1136/bmjophth-2018-000146">eye strain</a> or fatigue from looking at your screen for too long, they’re actually symptoms of a condition called <a href="https://doi.org/10.1177%2F107118139704100292">cybersickness</a>.</p>
<p>These issues may seem like a necessary evil with the rise of <a href="https://doi.org/10.1007/s10664-021-09945-9">work from home</a>, remote learning and days spent endlessly scrolling online. But I can assure you as a <a href="https://www.researchgate.net/profile/Angelica-Jasper">researcher in human computer interaction specializing in cybersickness</a> that there are ways to anticipate and avoid feeling sick from your screens.</p>
<h2>What is cybersickness?</h2>
<p><a href="https://doi.org/10.1177%2F107118139704100292">Cybersickness</a> refers to a <a href="https://doi.org/10.1207/s15327108ijap0303_3">cluster of symptoms</a> that occur in the absence of physical motion, similar to motion sickness. These symptoms fall into three categories: nausea, <a href="https://www.nature.com/subjects/oculomotor-system">oculomotor</a> issues and general disorientation. Oculomotor symptoms, like eye strain, fatigue and headaches, involve overworking the nerve that controls eye movement. Disorientation can manifest as dizziness and vertigo. And several cybersickness symptoms, such as difficulty concentrating and blurred vision, overlap categories. These issues can persist for hours and affect sleep quality. </p>
<p>People can experience symptoms of cybersickness through everyday devices like computers, phones and TV. For instance, Apple released a <a href="https://www.macworld.com/article/221315/inside-the-technology-behind-ios-7s-parallax-effect.html">parallax effect on iPhone lock screens</a> in 2013 that made the background image seem like it floated or shifted when a user moved their phone around, which many people found extremely uncomfortable. As it turns out, <a href="https://doi.org/10.1101/488817">this was because it triggered cybersickness symptoms</a>. <a href="https://xd.adobe.com/ideas/principles/web-design/best-practices-for-parallax-websites/">Parallax scrolling</a> on websites, where a background image remains static while foreground content moves as you scroll, can also elicit these symptoms. </p>
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<iframe width="440" height="260" src="https://www.youtube.com/embed/uTIzW5fZn_4?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">The parallax effect, commonly deployed in many websites and games to give an illusion of depth, can lead to cybersickness symptoms.</span></figcaption>
</figure>
<p>There isn’t total agreement among researchers about why people experience cybersickness. One prevailing idea, <a href="https://doi.org/10.1007/978-3-030-59342-1">sensory conflict theory</a>, hypothesizes that it’s from a mismatch of information perceived by the parts of the body that regulate vision and balance. Your eyes receive information that tells them you’re moving even though your body isn’t. Everyday technology design can trigger this conflict between visual perception and physical experience.</p>
<h2>Cybersickness in virtual and augmented reality</h2>
<p>Cybersickness symptoms tend to be more intense with <a href="https://www.wired.com/story/wired-guide-to-virtual-reality/">virtual reality</a> and <a href="https://www.businessinsider.com/what-is-augmented-reality">augmented reality</a>.</p>
<p>VR refers to technology that entirely blocks your view of the real world and replaces it with an immersive, artificial environment. It’s widely commercially available through popular gaming platforms like Facebook’s Oculus devices and Sony PlayStation VR. VR can result in <a href="https://doi.org/10.3389/fnhum.2020.00096">severe levels of nausea</a> that increase with duration of use. This can make certain applications and games unusable for many individuals. </p>
<p>AR, on the other hand, overlays a simulated environment onto the real world. These could include head-mounted devices that still allow you to see what’s in front of you or something like <a href="https://www.theverge.com/2020/5/26/21269862/niantic-pokemon-go-reality-blending-ar-features-release-update">Pokémon Go</a> on your phone or tablet. AR tends toward <a href="https://doi.org/10.3389/frvir.2020.602954">more severe oculomotor strain</a>.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/411946/original/file-20210719-13-ykmglo.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Hand holding up phone playing Pokémon Go" src="https://images.theconversation.com/files/411946/original/file-20210719-13-ykmglo.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/411946/original/file-20210719-13-ykmglo.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/411946/original/file-20210719-13-ykmglo.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/411946/original/file-20210719-13-ykmglo.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/411946/original/file-20210719-13-ykmglo.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/411946/original/file-20210719-13-ykmglo.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/411946/original/file-20210719-13-ykmglo.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">AR games, like Pokémon Go, can cause oculomotor symptoms like eye strain, fatigue and headaches.</span>
<span class="attribution"><a class="source" href="https://unsplash.com/photos/Am1io6KusFM">David Grandmougin/Unsplash</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>Even if you haven’t used VR or AR devices before, chances are you will <a href="https://www.researchandmarkets.com/reports/5240209/extended-reality-xr-market-by-component">within the next 10 years</a>. A rise in the popularity of AR and VR use will likely trigger a rise in cybersickness symptoms. Market research firm Research and Markets estimates that adoption of these technologies for work, education and entertainment may <a href="https://www.researchandmarkets.com/reports/5240209/extended-reality-xr-market-by-component">grow over 60% and reach over US$900 billion by 2027</a>.</p>
<h2>Cybersickness symptoms could be dangerous</h2>
<p>While cybersickness symptoms may initially appear benign, they can have enduring effects <a href="https://doi.org/10.1177%2F0018720811428734">lasting up to 24 hours after device use</a>. This may not seem like a big deal at first. But these lingering symptoms could affect your ability to function in ways that could prove dangerous.</p>
<p>For instance, symptoms like severe headache, eye strain or dizziness could affect your coordination and attention. If these side effects persist while you’re operating a vehicle, it could lead to a car accident. It’s unclear whether the user, software company or some other party would be <a href="https://www.washingtonpost.com/news/volokh-conspiracy/wp/2017/03/31/tort-lawsuits-against-vrar-companies-when-users-physically-injure-outsiders/">responsible</a> for <a href="https://www.lawtechnologytoday.org/2021/01/what-are-the-harmful-effects-of-virtual-reality/">injuries</a> potentially caused by device use and <a href="https://pipself.blogs.pace.edu/2017/02/25/foreseeable-lawsuits-for-virtual-reality/">cybersickness symptoms</a>.</p>
<p>Not much is currently known about how chronic cybersickness affects daily life. Just as there is extreme variability on who is more prone to motion sickness, with some up to <a href="https://doi.org/10.1007/s00221-014-4008-8">10,000 times more at risk</a>, some people may be more prone to cybersickness than others. Evidence suggests that <a href="https://doi.org/10.3389/frvir.2020.582108">women</a>, those who <a href="https://doi.org/10.3389/frvir.2020.582108">don’t play video games often</a> and people with <a href="https://doi.org/10.1097/00005537-200403000-00036">poor balance</a> may experience more severe cybersickness.</p>
<h2>Dealing with cybersickness symptoms</h2>
<p>If you are struggling with cybersickness symptoms because you’re using your computer or phone for longer periods, there are ways to help relieve the discomfort. <a href="https://doi.org/10.1111/j.1600-079X.2006.00332.x">Blue light glasses</a> are designed to block out some of the blue light waves emitted by your device screen that can lead to eye strain and sleep irregularities. <a href="https://doi.org/10.1111/cxo.12798">Zooming in on a screen or using larger font sizes</a> may also help reduce eye strain and make daily work more sustainable. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/411962/original/file-20210719-19-1cf3jll.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Person wearing extended reality headset in a library." src="https://images.theconversation.com/files/411962/original/file-20210719-19-1cf3jll.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/411962/original/file-20210719-19-1cf3jll.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/411962/original/file-20210719-19-1cf3jll.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/411962/original/file-20210719-19-1cf3jll.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/411962/original/file-20210719-19-1cf3jll.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/411962/original/file-20210719-19-1cf3jll.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/411962/original/file-20210719-19-1cf3jll.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">More people may begin to experience cybersickness symptoms as VR and AR devices become more common in everyday use.</span>
<span class="attribution"><a class="source" href="https://unsplash.com/photos/AplbmIMHwAE">stem.T4L/Unsplash</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>If you’re interested in trying VR and AR applications but are prone to motion sickness, warning indicators, like <a href="https://developer.oculus.com/policy/store-policies/">Oculus Comfort Ratings</a>, can help you know what to expect. Always make sure to <a href="https://www.automate.org/tech-papers/enabling-display-measurement-within-augmented-and-virtual-reality-headsets">visually calibrate devices</a> so your eyes are as comfortable as possible, and use devices only in <a href="https://www.classvr.com/health-and-safety/">open spaces</a> to minimize the risk of injury if you get dizzy and lose your balance. <a href="https://www.classvr.com/health-and-safety/">Take breaks</a> if you start to feel any discomfort.</p>
<h2>Using new technology safely</h2>
<p>The <a href="https://doi.org/10.1007/s10664-021-09945-9">work-from-home movement</a> has grown as a result of the COVID-19 pandemic. Many people have replaced 9-to-5’s and commutes with sweatpants, bedhead and Zoom meetings. Though the convenience is undeniable, it has also come with an increasing awareness of how difficult it can be to stare at a screen for 40-plus hours a week.</p>
<p>But don’t let cybersickness get you down. As researchers continue to find ways to mitigate and prevent cybersickness across all devices, people may one day be able to enjoy advancements in innovative technologies without feeling dizzy.</p><img src="https://counter.theconversation.com/content/163851/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Angelica Jasper works for Design Interactive, Inc. as a Research Associate. </span></em></p>If you ever felt nauseous, fatigued or disoriented after using your phone or computer, you may be experiencing a condition similar to motion sickness.Angelica Jasper, PhD, PhD Candidate in Human Computer Interaction, Iowa State UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1469562020-10-28T18:59:30Z2020-10-28T18:59:30ZDaylight saving time could be especially hard this weekend because of COVID-19 sleep loss<figure><img src="https://images.theconversation.com/files/389136/original/file-20210311-19-1mzgc1.jpg?ixlib=rb-1.1.0&rect=0%2C249%2C5357%2C3148&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption"> Sleep loss was an issue even before COVID-19. </span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/news-photo/news-photo/107693557?adppopup=true">Thurston Hopkins/Picture Post/Hulton Archive via Getty Images</a></span></figcaption></figure><p>The clock springs forward one hour on Sunday morning, March 14 for most people in the U.S. That is not an appealing thought for those who have suffered sleep problems because of the pandemic. </p>
<p>Sleep this past year has been affected by a variety of factors, including anxiety, inconsistent schedules and increased screen time. This affects our health, as getting adequate sleep is important to assure our immune system can fend off and fight infections. </p>
<p>Even before the pandemic, about 40% of adults – 50 to 70 million Americans – <a href="https://doi.org/%2010.17226/11617">got less than the recommended</a> minimum seven hours per night.</p>
<p>And, many researchers were already concerned about how the twice-a-year switch affects our body’s physiology. <a href="https://doi.org/10.5664/jcsm.8780">The American Academy of Sleep Medicine</a>, the largest scientific organization that studies sleep, in October 2020 suggested nixing daylight saving time and moving to a year-round fixed time. That way, our internal circadian clocks would not be misaligned for half the year. And it would eliminate the safety risk from sleep loss when transitioning to daylight saving time.</p>
<p><a href="https://neurology.ufl.edu/profile/jaffee-michael/">I am a neurologist</a> at the University of Florida. I’ve studied how a lack of sleep can impair the brain. In the 1940s, most American adults averaged 7.9 hours of sleep a night. Today, it’s only 6.9 hours. To put it another way: In 1942, 84% of us got the recommended seven to nine hours; in 2013, it was 59%. To break it down further, a January <a href="https://blog.fitbit.com/sleep-study/">2018 study from Fitbit</a> reported that men got even less sleep per night than women, about 6.5 hours. </p>
<figure class="align-center ">
<img alt="A 6-year-old needs 9-12 hours of sleep a day." src="https://images.theconversation.com/files/365135/original/file-20201023-15-1stabfx.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/365135/original/file-20201023-15-1stabfx.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/365135/original/file-20201023-15-1stabfx.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/365135/original/file-20201023-15-1stabfx.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/365135/original/file-20201023-15-1stabfx.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/365135/original/file-20201023-15-1stabfx.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/365135/original/file-20201023-15-1stabfx.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Children age 12 and under need 9-12 hours of sleep per night.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/boy-sleeping-in-bed-royalty-free-image/630159689?adppopup=true">Tetra Images/DigitalVision via Getty Images</a></span>
</figcaption>
</figure>
<h2>The case for sleep</h2>
<p>Problems from sleep shortage go beyond simply being tired. Compared to those who got enough sleep, adults who are short sleepers – those getting less than seven hours per day – <a href="https://www.nichd.nih.gov/health/topics/sleep/conditioninfo/inadequate-sleep">were more likely to report</a> 10 chronic health conditions, including heart disease, diabetes, obesity, asthma and depression. </p>
<p>Children, who need more sleep than adults, face even more challenges. <a href="https://jcsm.aasm.org/doi/10.5664/jcsm.5866">To promote optimal health</a>, 6- to 12-year-olds should sleep nine to 12 hours a day; teens from 13 to 18, eight to 10 hours. But a Sleep Foundation poll of parents says children are getting at least one hour less than that. And <a href="https://doi.org/10.1093/sleep/30.9.1079">researchers have found</a> that sleep deprivation of even a single hour can harm a child’s developing brain, affecting memory encoding and attentiveness in school.</p>
<p>Sleep affects <a href="https://theconversation.com/why-are-we-so-sleep-deprived-and-why-does-it-matter-91803">every one of our biological systems</a>. Serious consequences can result with poor sleep quality. Here’s a short list: <a href="https://doi.org/10.1378/chest.09-2954">Blood pressure</a> may increase. <a href="https://doi.org/%2010.2174/157340310790231635">Risk of coronary heart disease</a> could go up. Our endocrine system releases more cortisol, a stress hormone. We become more aroused by “fight or flight” syndrome. There’s a reduction of growth hormone and muscle maintenance. There’s a higher chance of increased appetite and weight gain. The body has less glucose tolerance and greater insulin resistance; in the long term, that means an increased risk for Type 2 diabetes. </p>
<p>Sleep deprivation is associated with increased inflammation and a decreased number of antibodies to fight infections. It may also cause a decrease in pain tolerance, reaction times and memory. Occupational studies show sleep loss can cause poor work performance, including more days missed and more car accidents.</p>
<p><a href="https://doi.org/10.1016/j.cophys.2019.10.020">Recent research suggests</a> the body’s waste removal process relies on sleep to get rid of harmful proteins from the brain, particularly abnormal variants of amyloid. These are the same proteins that are elevated in Alzheimer’s patients. <a href="https://www.alzforum.org/news/research-news/lymphatic-brain-drain-withers-aging-worsens-disease">Studies show</a> that older adults who sleep less have greater accumulation of these proteins in their brains.</p>
<p>On the other hand, getting enough sleep helps the body in many ways by protecting against some of these damaging effects and by boosting the immune system.</p>
<figure class="align-center ">
<img alt="Some educators worry about transporting schoolchildren at dusk." src="https://images.theconversation.com/files/365140/original/file-20201023-15-1lg3bgv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/365140/original/file-20201023-15-1lg3bgv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/365140/original/file-20201023-15-1lg3bgv.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/365140/original/file-20201023-15-1lg3bgv.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/365140/original/file-20201023-15-1lg3bgv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/365140/original/file-20201023-15-1lg3bgv.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/365140/original/file-20201023-15-1lg3bgv.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Some educators worry about the safety factor when transporting schoolchildren at dusk.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/diverse-group-of-happy-children-getting-on-school-royalty-free-image/1166892600?adppopup=true">FatCamera/E+/E+ via Getty Images</a></span>
</figcaption>
</figure>
<h2>The problem with DST</h2>
<p>Most of the risk associated with daylight saving time occurs in the spring, when we turn the clock forward and lose one hour of sleep. The idea of a national permanent year-round time has support, but disagreements exist on whether the fixed time should be standard time or daylight saving time.</p>
<p>[<em>Deep knowledge, daily.</em> <a href="https://theconversation.com/us/newsletters/the-daily-3?utm_source=TCUS&utm_medium=inline-link&utm_campaign=newsletter-text&utm_content=deepknowledge">Sign up for The Conversation’s newsletter</a>.]</p>
<p><a href="https://www.ncsl.org/research/transportation/daylight-savings-time-state-legislation.aspx">States advocating</a> for permanent daylight saving time are typically those that rely on tourism. Environmentalists, favoring less energy consumption from morning heating and evening air conditioning, <a href="https://savestandardtime.com/pdfs/kotchen_and_grant-2008_12.pdf">often support permanent standard time</a>. Religious groups, whose prayer times are linked to sundown and sunrise, <a href="https://vosizneias.com/2018/03/13/miami-floridas-proposed-change-to-permanent-daylight-savings-time-could-create-halachic-problems-for-jewish-community/">also tend to prefer</a> permanent standard time. <a href="https://savestandardtime.com/pdfs/mercury_news-2018.pdf">So do many educators</a>, opposed to transporting children to school during mornings when it’s still dark. </p>
<p>As you ponder what system is best for a national year-round standard, consider this: The American Academy of Sleep Medicine has recommended we go with permanent standard time – a better way to align with our natural circadian clock and minimize health and safety risks.</p>
<p>And just think: If we change to permanent standard time, then for the first time in decades, you won’t lose an hour of sleep every spring.</p>
<p><em>Editor’s note: This story is updated from its original version, which was published Oct. 28, 2020.</em></p><img src="https://counter.theconversation.com/content/146956/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Michael S. Jaffee does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Springing forward for daylight saving time will be especially hard this year due to sleep loss from COVID-19. Why does the US keep doing this?Michael S. Jaffee, Vice Chair, Department of Neurology, University of FloridaLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1242352019-10-11T13:03:57Z2019-10-11T13:03:57ZBlue light isn’t the main source of eye fatigue and sleep loss – it’s your computer<figure><img src="https://images.theconversation.com/files/296496/original/file-20191010-188807-u4v7v7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">While blue light has been blamed for sleep loss, it's not the only bad light.</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/man-front-computer-screen-dark-night-11514280?src=BLyrJPAqyFp0jEYxevcAxA-1-6">Chaoss/Shuttterstock.com</a></span></figcaption></figure><p>Blue light has gotten a bad rap, <a href="https://www.forbes.com/sites/fionamcmillan/2018/08/11/how-blue-light-damages-cells-in-your-eyes/">getting blamed for loss of sleep and eye damage</a>. Personal electronic devices <a href="https://doi.org/10.3389/fpubh.2015.00233">emit more blue light than any other color</a>. Blue light has a short wavelength, which means that it is high-energy and can damage the delicate tissues of the eye. It can also pass through the eye to the retina, the collection of neurons that converts light into the signals that are the foundation of sight.</p>
<p>Laboratory studies have shown that prolonged exposure to high-intensity blue light <a href="https://www.sciencedirect.com/science/article/pii/S1011134409000025?via%3Dihub">damages retinal cells</a> in mice. But, epidemiological <a href="https://doi.org/%2010.1016/j.ophtha.2004.10.047">studies on real people</a> tell a different story. </p>
<p>As an <a href="https://scholar.google.com/citations?user=thGgi2UAAAAJ&hl=en">assistant professor at The Ohio State University</a> College of Optometry, I teach and conduct vision research, including work with retinal eye cells. I also see patients in the college’s teaching clinics. Often, my patients want to know how they can keep their eyes healthy despite looking at a computer screen all day. They often ask about “blue-blocking” spectacle lenses that they see advertised on the internet. </p>
<p>But when it comes to protecting your vision and keeping your eyes healthy, blue light isn’t your biggest concern.</p>
<h2>Built-in protection</h2>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/296516/original/file-20191010-188814-2yoh66.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/296516/original/file-20191010-188814-2yoh66.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/296516/original/file-20191010-188814-2yoh66.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/296516/original/file-20191010-188814-2yoh66.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/296516/original/file-20191010-188814-2yoh66.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/296516/original/file-20191010-188814-2yoh66.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/296516/original/file-20191010-188814-2yoh66.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Sunlight has more blue light than your computer.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/close-portrait-beautiful-african-american-woman-387806866?src=W0qyo74vYxTxbsOSZ4sWfw-1-13">miamgesphotography/Shutterstock.com</a></span>
</figcaption>
</figure>
<p>One way to think about blue light and potential retinal damage is to consider the Sun. <a href="https://www.intechopen.com/books/biofuels-economy-environment-and-sustainability/the-possibility-of-future-biofuels-production-using-waste-carbon-dioxide-and-solar-energy">Sunlight</a> is mostly blue light. On a sunny afternoon, it’s nearly <a href="https://doi.org/10.7554/eLife.15392">100,000 times brighter</a> than your computer screen. Yet, few human studies have found <a href="https://jamanetwork.com/journals/jamaophthalmology/fullarticle/268111">any link</a> between sunlight exposure and the development of age-related macular degeneration, a retinal disease that leads to loss of central vision.</p>
<p>If being outside on a sunny afternoon likely doesn’t damage the human retina, then neither can your dim-by-comparison tablet. A theoretical study recently <a href="https://doi.org/10.1038/eye.2015.261">reached the same conclusion</a>.</p>
<p>So, why the disconnect between blue light’s effects on rodent eyes and human eyes?</p>
<p>Human eyes are different than rodent eyes. We have protective elements, such as <a href="https://doi.org/10.1038/sj.eye.6702780">macular pigments</a> and the natural blue-blocking ability of the <a href="https://doi.org/10.1113/jphysiol.1988.sp016935">crystalline lens</a>. These structures absorb blue light before it reaches the delicate retina. </p>
<p>That doesn’t mean you should throw away those sunglasses; they provide benefits beyond protecting your eyes from the Sun’s blue light. For example, wearing sunglasses <a href="https://doi.org/%2010.1074/jbc.M114.554410">slows down the development of cataracts</a>, which cloud vision.</p>
<h2>Feeling the blues</h2>
<p>Just because blue light isn’t harming your retina doesn’t mean your electronic devices are harmless, or that blue light doesn’t affect your eyes. Because of its wavelength, blue light does <a href="https://doi.org/10.1523/JNEUROSCI.21-16-06405.2001">disrupt healthy sleep physiology</a>. <a href="https://doi.org/10.1126/science.1067262">Blue-light-sensitive</a> cells, known as known as intrinsically photosensitive retinal ganglion cells, or ipRGCs, play a key role here, because they tell the brain’s master clock how light it is in the environment. That means, when you look at a brightly lit screen, these cells help set your internal clock for daytime-level alertness. </p>
<p>But these cells are sensitive to colors beyond blue because they also receive input from <a href="https://www.physiology.org/doi/full/10.1152/physrev.00013.2010?url_ver=Z39.88-2003&rfr_id=ori%3Arid%3Acrossref.org&rfr_dat=cr_pub%3Dpubmed">other retinal neurons</a> that are sensitive to the entire color spectrum. </p>
<p>Therefore, eliminating blue light alone doesn’t cut it when it comes to improving sleep; you need to dim all colors.</p>
<p>As for your tired eyes after a long day spent staring at your computer – another common complaint I hear from my patients – blue light isn’t solely to blame for that, either. A recent study demonstrated that cutting blue light alone <a href="https://doi.org/10.1097/OPX.0000000000001318">did not improve</a> people’s reported comfort after a long computer session any more than simply dimming the screen. </p>
<h2>Does blocking the blue make sense?</h2>
<p>Many patients want to know if they should buy certain products they have seen advertised to block out blue light. Based on research, the short answer is “no.” </p>
<p>First, the truth is that any bright light too close to bedtime interferes with sleep.</p>
<p><a href="https://doi.org/10.1073/pnas.1418490112">Mounting evidence</a> suggests that, compared to reading a paperback, screen time before bed increases the time it takes to fall asleep. It also robs you of restorative rapid-eye-movement sleep, dulls focus and diminishes brain activity the next day. Holding your phone close to your eyes with the lights on likely <a href="https://doi.org/10.1038/srep11325">exacerbates the problem</a>.</p>
<p>Second, the products that my patients ask about do not block out much blue light. The leading blue-blocking anti-reflective coating, for example, <a href="https://doi.org/10.1097/OPX.0000000000001393">blocks only about 15%</a> of the blue light that screens emit.</p>
<p>You could get the same reduction just by holding your phone another inch from your face. Try it now and see if you notice a difference. No? Then it shouldn’t surprise you that a recent meta-analysis concluded that blue-blocking lenses and coatings have <a href="https://doi.org/10.1111/opo.12406">no significant effect</a> on sleep quality, comfort at the computer, or retinal health.</p>
<h2>What really works</h2>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/296512/original/file-20191010-188823-19v26go.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/296512/original/file-20191010-188823-19v26go.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/296512/original/file-20191010-188823-19v26go.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/296512/original/file-20191010-188823-19v26go.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/296512/original/file-20191010-188823-19v26go.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/296512/original/file-20191010-188823-19v26go.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/296512/original/file-20191010-188823-19v26go.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Computers cause eye strain because people don’t blink as often when staring at a screen.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/young-woman-taking-off-glasses-tired-1075401764?src=kSqTmRfglJpQ53eQzQoDGQ-1-18">fizkes/Shutterstock.com</a></span>
</figcaption>
</figure>
<p>There are ways to make your screen viewing more comfortable and more conducive to sleep. </p>
<p>First, turn off your electronic devices before bed. The <a href="https://www.aap.org/en-us/about-the-aap/aap-press-room/Pages/American-Academy-of-Pediatrics-Announces-New-Recommendations-for-Childrens-Media-Use.aspx">American Academy of Pediatrics</a> recommends that bedrooms be “screen-free” zones for children, but we should all heed this advice. Outside of the bedroom, when you do look at your screens, lower the brightness. </p>
<p>As for eye strain, ensure that you have the appropriate glasses or contact lens prescription. Only an optometrist or ophthalmologist can give you this information.</p>
<p>You also need to take care of the surface of your eyes. We don’t just look at our computer screens, we stare at them. In fact, our <a href="https://doi.org/10.1007/s00417-003-0786-6">blink rate plummets</a> from about 12 blinks a minute to six. As a result, tears evaporate off the eyes, and they don’t accumulate again until we step away from the screen and start blinking. This causes inflammation on the eye’s surface. That’s why your eyes feel dry and tired after a day spent at the computer. I counsel my patients to take two steps to ensure that their eyes stay moist during long computer sessions.</p>
<p>First, follow the “20-20-20” rule. The <a href="https://www.aoa.org/documents/infographics/SYVM2016Infographics.pdf">American Optometric Association</a> defines this rule as taking a 20-second break every 20 minutes to look at something 20 feet in the distance. This will allow your eyes to blink and relax. There are many apps available to help remind you to follow this rule.</p>
<p>Second, use a lubricating eye drop before extended computer use. This tactic will reinforce the body’s natural tears and keep the eye’s surface hydrated. But, avoid those “get-the-red-out” drops. They contain drugs that cause long-term redness and preservatives that may <a href="https://www.sjeyeassociates.com/the-dangers-of-redness-relief-eye-drops/">damage the outer layers of the eye</a>. I have found that artificial tears labeled “preservative free” often work best.</p>
<p>Based on my research, my advice is don’t believe the hype about blue light and don’t waste your money on products you don’t need. Instead, keep screens out of your bedroom and dim them before bedtime and keep your eyes lubricated. And don’t forget to blink!</p>
<p>[ <em>Like what you’ve read? Want more?</em> <a href="https://theconversation.com/us/newsletters?utm_source=TCUS&utm_medium=inline-link&utm_campaign=newsletter-text&utm_content=likethis">Sign up for The Conversation’s daily newsletter</a>. ]</p><img src="https://counter.theconversation.com/content/124235/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Phillip Yuhas receives funding from the National Institutes of Health and the Ohio Lions Eye Research Foundation. He is a member of the American Optometric Association, the Ohio Optometric Association, the American Academy of Optometry, and the Association for Research in Vision and Ophthalmology. </span></em></p>Blue light has been getting blamed for sleep interruption and eye strain. But the facts are that any bright light interferes with sleep, and computers themselves cause eye strain, an eye doctor says.Phillip Yuhas, Assistant Professor of Optometry, The Ohio State UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1175272019-05-28T12:30:18Z2019-05-28T12:30:18ZLimiting screen use is not the way to tackle teenage sleep problems – here’s how to browse healthily at night<figure><img src="https://images.theconversation.com/files/276369/original/file-20190524-187143-36kurl.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/woman-watch-on-mobile-phone-lying-1277272681?src=n4z8B144zUfkKOVkWW_R3A-1-26">leungchopan/Shutterstock</a></span></figcaption></figure><p>Both in <a href="https://bmjopen.bmj.com/content/bmjopen/5/1/e006748.full.pdf">Europe</a> and the <a href="http://jcsm.aasm.org/viewabstract.aspx?pid=29249&k_clickid=%2Fwellness%2F">US</a>, more than 90% of adolescents have their faces buried in screens before bed. Often, this comes at a cost to sleep. Frequent screen users are much more likely to <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4437561/">report</a> falling asleep later, sleeping less, and <a href="https://psyarxiv.com/z7kpf/">waking</a> during the night. Such difficulties are linked not only to poorer <a href="https://www.ncbi.nlm.nih.gov/pubmed/29908393">academic performance</a>, but also increased risk of health issues such as diabetes and heart disease in <a href="https://www.ncbi.nlm.nih.gov/pubmed/29908393">later life</a>.</p>
<p>As a result, teenage screen use is treated as an unhealthy addiction among much of the media. But this narrative is based on a fundamental misunderstanding of the research. The problem isn’t use of screens at night, but how they’re used.</p>
<p>After a recent study <a href="https://www.eurekalert.org/pub_releases/2019-05/esoe-spi051519.php">demonstrated</a> that limiting screen use for a week could restore normal sleep patterns in adolescents, media headlines widely hailed this as the salvation for sleep-troubled teens. However, these headlines <a href="https://www.ecosia.org/news?q=Sleep+problems+in+teenagers+reversed+in+just+one+week+by+limiting+screen+use">almost exclusively</a> ignored the fact that wearing blue-light blocking goggles was just as effective.</p>
<p>Exposure to <a href="https://www.sciencedirect.com/science/article/pii/S0166432817311002?via%3Dihub">alertness-inducing</a> blue light is undoubtedly a problem – when it comes from our screens at night, it can disrupt the natural circadian rhythms that secrete sleep hormones to prepare our bodies for rest. But it’s also an easy issue to solve. Applications already exist on phones and laptops that shift the blueness of light with the time of day, sidestepping the somewhat unrealistic expectation of teenagers donning special goggles. </p>
<h2>Content is key</h2>
<p>There’s a much more urgent issue at the heart of the relationship between bedtime devices and sleep, not just in youth, but for all of us. The screens we watch are not devoid of content, and how we interact with them is key.</p>
<p>Passive activities such as reading neutral content are largely <a href="https://onlinelibrary.wiley.com/doi/full/10.1111/bjop.12351">unproblematic</a>, as long as care is taken to avoid keeping the brain whirring late into the night. The key area of concern is social media. Almost half of 13 to 17-year-olds admit to being online <a href="https://www.pewinternet.org/2018/05/31/teens-social-media-technology-2018/">almost constantly</a>, and these frequent users are much more likely to <a href="https://psyarxiv.com/z7kpf/">report</a> later sleep onset, as well as waking during the night.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/276377/original/file-20190524-187176-1hlxoz5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/276377/original/file-20190524-187176-1hlxoz5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/276377/original/file-20190524-187176-1hlxoz5.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/276377/original/file-20190524-187176-1hlxoz5.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/276377/original/file-20190524-187176-1hlxoz5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/276377/original/file-20190524-187176-1hlxoz5.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/276377/original/file-20190524-187176-1hlxoz5.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Blue light disrupts our body’s internal clock – but it’s an easy issue to solve.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/disappointed-sad-woman-holding-mobile-phone-1129353881?src=bevsZXQK-QW99AEDkE041g-1-0">tommaso79/Shutterstock</a></span>
</figcaption>
</figure>
<p>But these negative impacts are also dependent on our <a href="https://psyarxiv.com/z7kpf/">relationship</a> with social media, rather than our mere use of it. <a href="https://www.sciencedirect.com/science/article/pii/S0140197116300343">Work</a> from both our own lab and others suggests that the negative impacts of social media use on sleep quality may be a result of the anxiety, depression, and lowered self-esteem that it can <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2836296/pdf/1471-2458-10-66.pdf">induce</a>. Crucially, the negative mental health effects of social media are not inevitable, but dependent on the way we interact online. When used in the right way, screen use can actually be beneficial.</p>
<p>For example, time spent using image-based platforms like Instagram and Snapchat (but not text-based platforms like Twitter) is associated with <a href="https://www.sciencedirect.com/science/article/pii/S0747563216302552?via%3Dihub">decreased loneliness</a>, possibly due to an enhanced sense of intimacy and interconnectedness. However, this benefit is dependent on using the platform to interact with other people – those who simply broadcast content actually report <a href="https://www.ncbi.nlm.nih.gov/pubmed/27855266">increased loneliness</a>. It’s also dependent on following people you know – the more strangers you follow, the more likely you are to have <a href="https://www.ncbi.nlm.nih.gov/pubmed/25965859">depressive symptoms</a>.</p>
<p>It may also surprise you to know that making social comparisons is not always problematic – what’s important is how we make them. Ability-based comparisons, such as comparing oneself to “fitspiration” posts showing body images only a few of us have the time and ability to achieve, can lead to <a href="https://www.ncbi.nlm.nih.gov/pubmed/29327168">depression and envy</a>. Opinion-based comparisons, on the other hand, where social media users seek out the views of others to make sense of the world around them, can lead people to feel <a href="https://www.researchgate.net/publication/322415836_Social_Media_Social_Comparison_of_Ability_but_not_Opinion_Predicts_Lower_Identity_Clarity_Identity_Processing_Style_as_a_Mediator">inspired and optimistic</a>.</p>
<h2>Healthy nighttime browsing</h2>
<p>With that in mind, here are some tips based on the latest research on screen and social media use to help you make the best out of your evening browsing, and have a good night’s sleep.</p>
<figure class="align-right ">
<img alt="" src="https://images.theconversation.com/files/276792/original/file-20190528-42556-xwnh6o.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/276792/original/file-20190528-42556-xwnh6o.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=485&fit=crop&dpr=1 600w, https://images.theconversation.com/files/276792/original/file-20190528-42556-xwnh6o.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=485&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/276792/original/file-20190528-42556-xwnh6o.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=485&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/276792/original/file-20190528-42556-xwnh6o.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=610&fit=crop&dpr=1 754w, https://images.theconversation.com/files/276792/original/file-20190528-42556-xwnh6o.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=610&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/276792/original/file-20190528-42556-xwnh6o.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=610&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Leaving social media until the morning isn’t essential, but its still a good way of disconnecting.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/addicted-social-media-young-man-falling-1386129215?src=9Ed7hUBv7D7Dg4OEGV32ww-1-4">Sam Wordley/Shutterstock</a></span>
</figcaption>
</figure>
<p>• Use your platforms to create communities and maintain connections through interaction – too much silent browsing and self-broadcasting can harm your peace of mind, and therefore your ease of sleep. And remember – the best selves you see are not representative of real life.</p>
<p>• Try to reserve the last half an hour before bed not doing anything too stimulating. Putting the phone down a little while before bed is a good habit to get into, but if you are going to use it, use a blue-light blocking app, and do something passive and unemotional that will allow the sleepy feeling to come.</p>
<p>• If you think that activities are getting in the way of you feeling sleepy, or that household bedtime routines do not match your rhythm, then talk to someone. Sleep is important but parents sending teens off to bed before they’re ready is not always the best plan.</p>
<p>We need to move away from the dominant narrative of screen and social media use as an evil, as a hindrance to healthy development. Our bedtime devices needn’t be guilt-inducing vices. The online world is rich and diverse.</p>
<p>Like any social interaction, social media use can be damaging if navigated in the wrong way, but the virtual world it opens up can also be fulfilling, informative, and empowering. So let’s create a society that uses it healthily – not just by blocking out blue light, but by blocking out the things that make you see yourself in a blue light.</p><img src="https://counter.theconversation.com/content/117527/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Holly Scott receives funding from the UK Economic and Social Research Council. </span></em></p><p class="fine-print"><em><span>Heather Cleland Woods does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Many adolescents have trouble sleeping - but limiting screen use is not the solution. When used correctly, bedtime use of devices can be beneficial to mental health, without harming sleep quality.Heather Cleland Woods, Lecturer in Psychology, University of GlasgowHolly Scott, PhD Candidate in Psychology, University of GlasgowLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/831432018-01-15T19:06:43Z2018-01-15T19:06:43ZI’ve always wondered: why do our veins look blue when our blood is red?<figure><img src="https://images.theconversation.com/files/201249/original/file-20180108-83559-cyw7s1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Our veins only appear blue through the skin, they're actually red. </span> <span class="attribution"><span class="source">from www.shutterstock.com</span></span></figcaption></figure><p><em>This is an article from I’ve Always Wondered, a series where readers send in questions they’d like an expert to answer. Send your question to alwayswondered@theconversation.edu.au</em></p>
<hr>
<p><strong>I’ve always wondered why our veins are blue, when blood is red? - Alexandra, 28, Melbourne</strong></p>
<p>Blood is red, and a surgeon will tell you our veins too are red, they only look blue when we see them through our skin. But why?</p>
<p>The answer depends on a number of things, including how your eyes perceive colour, how light behaves when it contacts your body, and the special properties of blood.</p>
<p>Light travels in peaks and troughs. And the distance between each trough is called a wavelength. Different colours of light have waves of different lengths. Red light has a long wavelength (about 700 nanometres), violet light has a short wavelength (about 400 nanometres), and the rest of the spectrum is spread out in between.</p>
<p><img width="100%" src="https://media.giphy.com/media/12Yf5CuhUpjDG0/giphy.gif"></p>
<p>We see something as a particular colour when light of that colour hits our eyes –either directly from a light source or reflected from a surface.</p>
<p>To understand what colour our veins appear, we need to think about what happens to different wavelengths of light when they hit our skin, how far they can travel through our skin, and what happens when they get to our veins.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/curious-kids-why-are-rainbows-round-81187">Curious Kids: Why are rainbows round?</a>
</strong>
</em>
</p>
<hr>
<p>The light that hits our skin during the day is basically white, which is a mixture of all the visible wavelengths. But to explain why our veins look blue, we will look at just the red and blue ends of the spectrum.</p>
<p>Red light has a long wavelength – and this means it is less likely to be deflected by materials and can more easily travel through. Red light can travel pretty well through the skin and body tissues, reaching up to 5-10mm below the skin, which is where many veins are.</p>
<p>When it gets to the veins, the red light is absorbed by the haemoglobin (the protein that makes our blood red). You can demonstrate this to yourself. If you shine a red light on your arm, you will see some red light reflected back, and dark lines where the veins are, as the red light is absorbed by the haemoglobin.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/explainer-whats-actually-in-our-blood-75066">Explainer: what's actually in our blood?</a>
</strong>
</em>
</p>
<hr>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/NS68ePykav0?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Red light makes our veins appear as dark lines.</span></figcaption>
</figure>
<p>This phenomenon is actually used to help medical personnel find veins to take blood – by shining red, and sometimes infrared (which is an even longer wavelength) light on the arm.</p>
<p>Blue light has a short wavelength (about 475 nanometres), and is scattered or deflected much more easily than red light. Because it’s easily scattered it doesn’t penetrate so far into the skin (only a fraction of a millimetre). When blue light hits the skin, it’s mostly deflected back. </p>
<p>If you shine a blue light on your skin, what you see is basically blue skin, and veins are hard to find. You may have seen blue light used in spaces such as public bathrooms to discourage intravenous drug use.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/201103/original/file-20180108-83547-pr38y0.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/201103/original/file-20180108-83547-pr38y0.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/201103/original/file-20180108-83547-pr38y0.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=449&fit=crop&dpr=1 600w, https://images.theconversation.com/files/201103/original/file-20180108-83547-pr38y0.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=449&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/201103/original/file-20180108-83547-pr38y0.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=449&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/201103/original/file-20180108-83547-pr38y0.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=565&fit=crop&dpr=1 754w, https://images.theconversation.com/files/201103/original/file-20180108-83547-pr38y0.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=565&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/201103/original/file-20180108-83547-pr38y0.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=565&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Blue lighting is used in some spaces to discourage intravenous drug use as it makes it harder to find veins.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Tampere_station_WC.jpg">Wikimedia Commons</a></span>
</figcaption>
</figure>
<p>So, now imagine the red light and the blue light shining on your skin at once, as happens when you are under white light. You will have a mixture of red, blue and other colours reflected back where there are no veins. Where there are veins, you will see relatively less red, and relatively more blue compared to the surrounding skin.</p>
<p>This means your veins will appear blue compared to the rest of your skin.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/201297/original/file-20180109-83559-19kt3yi.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/201297/original/file-20180109-83559-19kt3yi.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=397&fit=crop&dpr=1 600w, https://images.theconversation.com/files/201297/original/file-20180109-83559-19kt3yi.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=397&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/201297/original/file-20180109-83559-19kt3yi.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=397&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/201297/original/file-20180109-83559-19kt3yi.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=500&fit=crop&dpr=1 754w, https://images.theconversation.com/files/201297/original/file-20180109-83559-19kt3yi.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=500&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/201297/original/file-20180109-83559-19kt3yi.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=500&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption"></span>
<span class="attribution"><span class="source">The Conversation</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>Interestingly, the effect varies depending on how deep the vein is, and also on <a href="https://www.ncbi.nlm.nih.gov/pubmed/21085227">how thick the vein is</a>. Very narrow veins close to the surface, such as the capillary bed, will not appear blue.</p>
<p>Blue veins appear more prominent in very pale skinned people, and this may have given rise to the expression “blue blood” for European nobility in the 19th century. These people were untanned from manual labour, and so their veins appeared blue under the skin.</p>
<hr>
<p><em>With thanks to Science Writer at the Australian Red Cross Blood Service Alison Gould.</em></p>
<hr>
<p><em>* Email your question to alwayswondered@theconversation.edu.au
<br>
* Tell us on <a href="https://twitter.com/ConversationEDU">Twitter</a> by tagging <a href="https://twitter.com/ConversationEDU">@ConversationEDU</a> with the hashtag #alwayswondered, or
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<p class="fine-print"><em><span>David Irving does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Blood is red, but our veins are blue. Or are they?David Irving, Adjunct Professor, University of Technology SydneyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/673562016-11-04T17:59:07Z2016-11-04T17:59:07ZUnderstanding the genes that make our circadian clocks tick<figure><img src="https://images.theconversation.com/files/144483/original/image-20161103-25346-xnq2es.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Time to get up.</span> <span class="attribution"><a class="source" href="http://www.shutterstock.com/downloading_tips.mhtml?code=&id=334996769&size=huge&image_format=jpg&method=download&super_url=http%3A%2F%2Fdownload.shutterstock.com%2Fgatekeeper%2FW3siZSI6MTQ3ODIzMjI0NCwiYyI6Il9waG90b19zZXNzaW9uX2lkIiwiZGMiOiJpZGxfMzM0OTk2NzY5IiwiayI6InBob3RvLzMzNDk5Njc2OS9odWdlLmpwZyIsIm0iOiIxIiwiZCI6InNodXR0ZXJzdG9jay1tZWRpYSJ9LCJEdmQwYVFyemY1QXh1ZFdFUHhvcW8xczVRbGMiXQ%2Fshutterstock_334996769.jpg&racksite_id=ny&chosen_subscription=redownload_standard&license=standard&src=hOPPO2lXTzgMNTmHceZr-A-1-47">alarm clock image via www.shutterstock.com</a></span></figcaption></figure><p>Have you ever wondered why you don’t feel tired until late at night but your spouse is fast asleep at 10 p.m. and wakes spontaneously at 6 a.m.? </p>
<p>We each have an internal biological clock, called a circadian clock, that organizes the internal and external activities of our body around the 24-hour day. </p>
<p>While these clocks can be influenced by exposure to sunlight and electric light, for instance, our genes also play a role in how they function. That’s part of the reason that sleep and wake habits can vary from individual to individual. And that may also explain why certain chronotherapies, which help change the timing of the circadian clock, such as light boxes and taking the natural hormone melatonin as a supplement, vary in dose and effectiveness from person to person. </p>
<p>Circadian clocks are found in individual cells of our body. My <a href="http://www.ndbiology.com/duffield-lab/">research team</a> at the University of Notre Dame is teasing apart the molecular mechanisms of these cellular clocks, looking at how genes and the proteins they produce control the multitude of 24-hour rhythms in our bodily functions. </p>
<p>We think that an improved understanding of the circadian system, from genes through to physiology and behavior, will allow for the development of new and improved chronotherapies. </p>
<h2>How do circadian clocks work?</h2>
<p>At <a href="http://hmg.oxfordjournals.org/content/15/suppl_2/R271.full">least 15 genes</a> are thought to make up the cogs of the circadian clock mechanism. Natural genetic variations in these components can result in profound differences in circadian clocks from person to person. This is why some people have a short circadian clock cycle length or a long cycle length, and why some people are early birds and others are night owls.</p>
<p>Some of these genes and the proteins they produce form a series of interacting molecular pathways that then loop back on one another. The temporal pattern of genes being switched on and off starts afresh once every 24 hours, giving us a near perfect daily clock.</p>
<p>Circadian clocks do more than tell us when to feel sleepy and when to wake up. They are found in almost all organ systems of our body, such as in the brain, heart and liver. The clocks then modify cellular processes across the day that are specific to each tissue. When these organ systems are not in sync with one another, which can occur during shift work and jet lag, it can contribute to health problems. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/144484/original/image-20161103-25353-4eagxh.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/144484/original/image-20161103-25353-4eagxh.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=384&fit=crop&dpr=1 600w, https://images.theconversation.com/files/144484/original/image-20161103-25353-4eagxh.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=384&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/144484/original/image-20161103-25353-4eagxh.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=384&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/144484/original/image-20161103-25353-4eagxh.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=482&fit=crop&dpr=1 754w, https://images.theconversation.com/files/144484/original/image-20161103-25353-4eagxh.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=482&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/144484/original/image-20161103-25353-4eagxh.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=482&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Out of sync.</span>
<span class="attribution"><a class="source" href="http://www.shutterstock.com/pic-204951673/stock-photo-world-business-or-travel-concept.html?src=7efDO7sBpmaEfxs6v3GFXA-1-1">Clocks image via www.shutterstock.com.</a></span>
</figcaption>
</figure>
<h2>Coordinating the internal clocks is key</h2>
<p>The clock in the liver, for example, controls many of the biological
processes involved in the storage and release of energy molecules. The circadian rhythms in these cells are in tune with other organ systems in the body, such as fat cells and the brain.</p>
<p>Much of the function of the liver is given over to storing food molecules when they are in abundance, such as when we have just eaten a meal. The liver then mobilizes nutrients when we are fasting while we sleep.</p>
<p>If you eat in the middle of night, for example, that can throw off the body’s processes for storing these nutrients appropriately. Shift work and jet lag can result in metabolic problems because the timing of processes between organ systems is no longer correctly coordinated, and timing between those systems and the external environment is disrupted. The long-term ramifications of such poor coordination between our internal clocks and the external environment can result in the development of abnormal physiology, and ultimately disorders such as obesity and diabetes. </p>
<p>In fact, the incidence of cardiovascular and metabolic disease, obesity and diabetes is <a href="http://dx.doi.org/10.1186/s13098-015-0041-4">elevated in shift workers</a>, who account for about <a href="http://www.bls.gov/news.release/flex.nr0.htm">15 percent of the work force</a>. </p>
<p>Getting all of these processes on the same temporal track and in sync with the time zone you are functioning in is the key. So looking at the genes that play a role in how these clocks work can help us understand how they stay in sync. </p>
<p>Gaining a better sense of what genes are involved in regulating these circadian clocks could put us on a path to find better treatments and therapies to help people adjust to time shifts.</p>
<h2>Uncoupling the genetic brakes of the circadian clock</h2>
<p>Our lab in collaboration with the University of Oxford and Hoffmann-La Roche has identified a new biological pathway involved in resetting the circadian clock, which <a href="http://dx.doi.org/10.1016/j.cell.2013.08.004">was published in the journal Cell</a>. </p>
<p>We have found that preventing a gene called SIK1 from being expressed or inactivating the protein it produces can ease the effects of jet lag. </p>
<p>This is a remarkable finding because it reveals a new biological pathway that controls the clock resetting mechanism and because the protein that SIK1 expresses is a kinase enzyme. Protein kinases form one of the most common classes of drug targets, which makes the SIK1 protein an attractive target for pharmacological manipulation.</p>
<p>Our lab has also revealed a unique role for a gene called ID2 in regulating how <a href="http://dx.doi.org/10.1016/j.cub.2008.12.052">light resets the circadian clock</a> and how the clock can control downstream processes, including shaping the 24 hour rhythms of <a href="http://www.jbc.org/content/284/46/31735.long">fat and sugar metabolism</a> </p>
<p>In animals we have found that the absence of <a href="http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0073064">ID2 disrupts the normal cycle of feeding</a>, and makes the animals both <a href="https://www.hindawi.com/journals/jdr/2016/6785948/">lean</a> and <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4262528/">super-sensitized to insulin</a>. This suggests that ID2 could be an important therapeutic target for resetting circadian clocks as well as controlling metabolic disorders, such as obesity and diabetes. </p>
<p>Animals that are missing the ID2 gene are also highly responsive to resetting of the clock by light. Instead of taking a week to adjust to a new time zone, they adapt in one to two days. Both ID2 and SIK1 appear to function as natural brakes on the resetting mechanism of the clock, and in principle could one day be drug targets for adjusting our biological rhythms.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/144485/original/image-20161103-25349-pow0th.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/144485/original/image-20161103-25349-pow0th.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/144485/original/image-20161103-25349-pow0th.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/144485/original/image-20161103-25349-pow0th.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/144485/original/image-20161103-25349-pow0th.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/144485/original/image-20161103-25349-pow0th.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/144485/original/image-20161103-25349-pow0th.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Bright light at night can shift our clocks in the wrong direction.</span>
<span class="attribution"><a class="source" href="http://www.shutterstock.com/pic-391673578.html">Exhausted woman image via www.shutterstock.com.</a></span>
</figcaption>
</figure>
<h2>Bright light in the morning, and dark at night</h2>
<p>While this research is promising, treatments using this research are probably still some time off. </p>
<p>In the meantime, there are a few things you can do to help keep your internal clocks in sync and on track, and adjust to disruptions more quickly. Chronotherapies, like timed exposure to light and taking melatonin supplements, can help change the timing of the circadian clock. These methods can prevent or reduce the problems that jet lag or shift work can cause, and assist in the treatment of seasonal affective disorder.</p>
<p>Because the light of dawn resets our body clock and keeps us in sync with the outside world, getting a good dose of morning light is critical.</p>
<p>Waking in pitch darkness and driving to work in the dark does not help. Just because it says 7 a.m. on the alarm clock does not mean it is 7 a.m. in your body. Exposure to <a href="https://theconversation.com/a-dark-night-is-good-for-your-health-39161">bright light at night</a>, including that emitted from electronic gadgets, can shift your biological clock in the wrong direction, making it even harder to get up the next day. Some of us are fighting our physiology every day. </p>
<p>Keeping yourself on a fixed routine of going to sleep at the same time can also be beneficial.</p><img src="https://counter.theconversation.com/content/67356/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Giles E. Duffield receives funding from the National Institutes of Health and has received funding from the American Heart Association. </span></em></p>Gaining a better sense of what genes are involved in regulating circadian clocks could put us on a path to find better treatments and therapies to help people adjust to time shifts.Giles E. Duffield, Associate Professor in Biological Sciences, University of Notre DameLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/498382015-11-09T03:55:14Z2015-11-09T03:55:14ZThere’s a fly in the ointment of solar-powered LED lighting<figure><img src="https://images.theconversation.com/files/101029/original/image-20151106-16273-2wpa0k.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Disase carrying insects are attracted to light bulbs – a constraint of domestic solar energy.</span> <span class="attribution"><span class="source">Jon Nazca/Reuters</span></span></figcaption></figure><p>Household air pollution is estimated to <a href="http://www.who.int/phe/health_topics/outdoorair/databases/HAP_BoD_results_March2014.pdf?ua=1">kill more than 500,000 people</a> in Africa each year. Through solar energy, people can stop using dirty and extremely polluting fuels like kerosene in their homes. But with domestic solar energy comes an unintended consequence. When the light bulbs are switched on, they can attract disease carrying bugs.</p>
<p>Given the health threats of kerosene and other indoor pollutants, a number of initiatives are driving the use of solar power for domestic uses. Organisations associated with the UN <a href="http://se4all.org/">Sustainable Energy For All</a> initiative are promoting various programmes. </p>
<p>And donors are also moving into this space. One example is the <a href="https://www.gov.uk/government/news/solar-boost-to-release-africas-untapped-energy-potential">EnergyAfrica</a> campaign being driven by UK’s Department for International Development, or DFID. Its focus is on domestic solar, providing individual householders with systems to power small electrical devices in the home. This mainly involves light bulbs.</p>
<p>The irradiation potential for sunshine to provide this form of clean energy in Africa is <a href="http://solargis.info/doc/_pics/freemaps/1000px/ghi/SolarGIS-Solar-map-Africa-and-Middle-East-en.png">substantial</a>. There will undoubtedly be enormous health benefits provided that people switch from kerosene and other so-called dirty fuels, instead of adding solar to the mix of energy types they use.</p>
<h2>So what’s the problem?</h2>
<p>Let’s temporarily set aside the potential problems of <a href="http://www.cgdev.org/blog/dfid-energy-africa-campaign-launch-three-facts-one-bad-idea-one-way-forward">financing</a> and sustainability for individual householders unused to looking after complete solar systems. There is one glaring issue with providing electrical light into otherwise non-improved residences like mud huts with corrugated iron roofs: flying insects.</p>
<p>Many different types of insects are attracted to light sources. This is either in search of a mate or after taking a meal. Many insects attracted to lights may be harmless, but key species are known vectors of disease that affect both humans and animals. These include:</p>
<ul>
<li><p>domestic flies, which carry the bacteria that cause blinding <a href="http://www.who.int/topics/trachoma/en/">trachoma</a>;</p></li>
<li><p>mosquitoes, which carry the parasites that cause <a href="http://www.who.int/topics/malaria/en/">malaria</a>, <a href="http://www.who.int/topics/filariasis/en/">filariasis</a>, <a href="http://www.who.int/topics/dengue/en/">dengue</a>; and</p></li>
<li><p><a href="http://www.parasitesandvectors.com/content/6/1/341">sandflies</a>, which carry the parasites that cause <a href="http://www.who.int/topics/leishmaniasis/en/">leishmaniasis</a>.</p></li>
</ul>
<p>Ironically, it is low-energy LED light bulbs that are the <a href="http://www.esajournals.org/doi/full/10.1890/14-0468.1">most attractive</a> due to the fact that they emit more blue light. This is such a major issue that attempts are underway to <a href="http://rstb.royalsocietypublishing.org/content/370/1667/20140125">tune LEDs</a> so that they attract a smaller number of flying insects.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/101031/original/image-20151106-16239-1y53v0s.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/101031/original/image-20151106-16239-1y53v0s.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/101031/original/image-20151106-16239-1y53v0s.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/101031/original/image-20151106-16239-1y53v0s.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/101031/original/image-20151106-16239-1y53v0s.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/101031/original/image-20151106-16239-1y53v0s.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/101031/original/image-20151106-16239-1y53v0s.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Blue light
that attracts vector carrying flying insects.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure>
<h2>Artificial light + human odours + evolution = trouble</h2>
<p>Mosquitoes are not just attracted to light. They also seek out human skin due to the <a href="http://link.springer.com/article/10.1007%2Fs10886-014-0542-x">CO2</a> released by our bodies when we breathe, and are attracted to <a href="http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0015829">chemicals</a> released by skin bacteria. </p>
<p>Historically, this may not have been a major issue because mosquitoes tend to feed after midnight. But mosquito populations may have evolved to seek blood-meals <a href="http://www.sciencedirect.com/science/article/pii/S0001706X15300577">earlier in the night</a> due to the selective pressure of bed nets. In addition, the <a href="http://www.ncbi.nlm.nih.gov/pubmed/25597498">efficiency</a> of transmission from humans to mosquitoes may have increased over recent decades. This again is due to the pressure of control measures against the parasite.</p>
<p>So what might happen if the introduction of artificial light, using low-energy LEDs, is combined with other interventions?</p>
<p>Research is still at an early stage. On the one hand, <a href="http://www.malariajournal.com/content/14/1/209">modern housing</a> may reduce the risk of malaria. But there is already some epidemiological evidence that electrification of community buildings and neighbourhoods may accidentally <a href="http://trstmh.oxfordjournals.org/content/104/1/61.long">increase the risk of malaria</a> and <a href="http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2974685/">other diseases</a>. </p>
<p>Some of these effects may be directly as a result of lights attracting vectors of disease to places where humans are present. Alternatively, the vectors may not be attracted to light itself but to humans who are undertaking domestic and economic activities near to a source of artificial light. This may be happening even as the harmful effects of particulates from kerosene lamps are reduced. </p>
<h2>Joining the dots</h2>
<p>To find solutions to this double-edged sword we can first turn to the field of <a href="http://www.biomedcentral.com/1741-7015/11/116">Evolutionary Medicine</a>. This considers how evolutionary processes shape our ability to combat disease. Research in this field can be combined with an integrated approach involving <a href="https://theconversation.com/an-integrated-sustainable-fix-is-key-to-solving-africas-energy-woes-48256">sustainable buildings</a>, and <a href="http://www.sciencedirect.com/science/article/pii/S2214629614001431">sociotechnical</a> research to tackle both energy and health issues simultaneously. </p>
<p>At the heart of that idea is the fact that solar power, when integrated into modern, energy-efficient buildings, can be used entirely off grid to bring electricity to <a href="http://app-cdn.acwupload.co.uk/wp-content/uploads/2015/06/APP_REPORT_2015_FINAL_low1.pdf">hundreds of millions</a> of people in Africa who lack access to energy. Many of these people live in areas where vector borne diseases are common.</p>
<p>Such an integrated approach needs careful planning and will not provide solutions at the same pace as providing small-scale solar systems to individual householders. This is probably why DFID is now behind small-scale solar. The technology has overcome historic barriers of affordability, availability and energy storage and can be installed into otherwise unimproved residences.</p>
<p>DFID is keen to open up the market to businesses in the solar sector. I am keen to ensure that the evidence base keeps on building so that the public, private and civil sectors are informed about the consequences and impact of their activities. </p>
<p>More generally, forewarned is forearmed, and by conducting research and examining the evidence ahead of wide-scale implementation, we can generate testable hypotheses and combine basic, applied, operational and implementation research to greater effect.</p><img src="https://counter.theconversation.com/content/49838/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Mark Booth does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Solar is a vital piece of the energy puzzle for Africa, but there is an insect problem that comes with the light from solar.Mark Booth, Senior Lecturer in Epidemiology, Durham UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/494122015-10-26T10:10:50Z2015-10-26T10:10:50ZAre we sleep-deprived or just darkness-deprived?<figure><img src="https://images.theconversation.com/files/99231/original/image-20151021-15416-g6vkea.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Not dark enough.</span> <span class="attribution"><a class="source" href="http://www.shutterstock.com/pic-270171140/stock-photo-mother-with-using-modern-devices-before-sleep.html?src=L8gIiSXUyS2v9zc5-hXH9A-6-46">People in bed via www.shutterstock.com.</a></span></figcaption></figure><p>The Centers for Disease Control and Prevention (CDC) state that insufficient sleep is a <a href="http://www.cdc.gov/features/dssleep/">serious public health concern</a>, because it can lead to many immediate dangers such as <a href="http://drowsydriving.org/about/facts-and-stats/">car crashes</a> as well as long-term health <a href="http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2276127/">problems like diabetes</a>. The blame for sleep deprivation is often pinned on our fast-paced, 24/7 lifestyle, made possible by electric lighting at all times of day and night.</p>
<p>But are we really getting too little sleep? </p>
<p>A <a href="http://dx.doi.org/10.1016/j.cub.2015.09.046">new study</a> challenges that idea from a unique perspective, and it is getting wide <a href="https://www.google.com/#q=jerome+siegel+sleep&tbm=nws">media attention</a>. </p>
<p>Researchers, led by Jerome Siegel at UCLA, followed three small preindustrial societies, two in Africa and one in South America, reasoning that the best way to judge whether sleep habits in the industrialized world are unnatural is to compare them to sleep habits in those few remaining societies on Earth that still live without electricity. </p>
<p>They found that the average period of time people spent trying to sleep was 7-8½ hours each night. Of this, only 5½-7 hours was confirmed as time asleep. This is about the same as, or less than, what is reported by most Americans and Europeans, and is considered <a href="https://sleepfoundation.org/excessivesleepiness/how-sleep-works/how-much-sleep-do-we-really-need">too little for optimum health</a>. </p>
<p>So maybe 5½-7 hours of sleep is natural and not the problem the CDC and many other health organizations say it is. </p>
<p>However, a crucial aspect of the findings of the new study has not been discussed in either the news stories or the paper itself: people in preindustrial societies spend much more time in darkness than people living in the industrialized world.</p>
<h2>What does this study tell us about sleep patterns?</h2>
<p>Besides finding that people in preindustrial societies without electricity sleep about the same amount as people in the electrified world, researchers also found that sleep didn’t start until several hours after sunset, although almost everyone woke up close to sunrise. </p>
<p>The researchers looked at temperature fluctuations, finding that it influenced the time of awakening in the morning. But for people sleeping in the modern built environment, temperature fluctuations in our bedrooms are minimal. </p>
<p>The researchers also found sleep in these societies was usually interspersed with periods of awakening that lasted for over an hour. These routine awakenings call into question the conventional wisdom that “ideal” sleep should be compacted into one stretch. Waking for a while at night is not necessarily a sleep disorder. Compacted sleep (“sleeping like a log”) is evidently not the way in which sleep evolved in humans.</p>
<p>But the big difference between sleep in the industrial world and sleep in the preindustrial world is about light and darkness. Electric light can delay or shut down nighttime physiology, whereas light from a wood fire or flame cannot. The researchers did not directly assess the quality of sleep, and this may be the part that matters.</p>
<p>The subjects in the preindustrial societies, living close to the equator, were exposed to darkness (with maybe an occasional wood fire) for 11 or 12 hours each night. In industrialized societies, people are typically exposed to darkness only as long as they are trying to sleep, often about seven hours. </p>
<h2>Normal sleep and nighttime physiology</h2>
<p>We humans have an endogenous circadian rhythmicity in physiology that is adapted to the solar cycle of day and night (as does almost all life on the planet). This means that in constant darkness we would still cycle about 24 hours in body temperature, hunger, activity and sleep.</p>
<p>When the sun is up, we are in daytime physiology: alert, active and hungry. When the sun sets in the evening, we begin the transition to nighttime physiology: body temperature drops, metabolism slows and sleepiness builds. In the world before electricity, each lasted about 11 hours near the equator, with time also for the transitions from one to the other at dawn and dusk. Of course, farther from the equator, the length of night increases or decreases according to season.</p>
<p>Part of nighttime physiology is sleep, but it is difficult to define what “normal” sleep is. Until the late 20th century, sleep was ignored by most biologists because it’s hard to study, and was thought by many ambitious people to be a vast waste of time. In recent years, this attitude has <a href="http://www.huffingtonpost.com/entry/arianna-huffington-parade-cover_55a67725e4b0896514cfe731">changed radically</a>. It is now believed that modern life has led to unhealthy sleep habits and widespread sleep deprivation with a multitude of adverse health and productivity consequences.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/99230/original/image-20151021-15451-51cw0x.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/99230/original/image-20151021-15451-51cw0x.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/99230/original/image-20151021-15451-51cw0x.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/99230/original/image-20151021-15451-51cw0x.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/99230/original/image-20151021-15451-51cw0x.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/99230/original/image-20151021-15451-51cw0x.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/99230/original/image-20151021-15451-51cw0x.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Blue light disrupts melatonin production.</span>
<span class="attribution"><a class="source" href="http://www.shutterstock.com/pic-226756855/stock-photo-young-teen-sleeping-front-of-a-laptop-computer-and-on-a-bed-photo-of-a-young-teen-sleeping-in-front.html?src=L8gIiSXUyS2v9zc5-hXH9A-4-67">Sleeping boy via www.shutterstock.com.</a></span>
</figcaption>
</figure>
<h2>Looking at sleep in the industrialized world</h2>
<p>In 1991, Thomas Wehr, a prominent sleep researcher, published the results of a <a href="http://dx.doi.org/10.1111/j.1365-2869.1992.tb00019.x">landmark experiment</a> he conducted in Bethesda, Maryland. In a sense, it mimicked sleep in the preindustrial world where there are naturally long, dark nights – the environment studied directly by Siegel and colleagues.</p>
<p>First, seven volunteers spent eight hours in the dark at night in the laboratory for four weeks; they then switched to 14 hours of dark each night without access to clocks and alarms. During the short nights, they slept a little more than seven hours on average. During the long nights they slept only about an hour more, a little over eight hours, and the sleep was broken into two stretches with an hour or two awake in between. </p>
<p>Importantly, the duration of melatonin production increased by about two hours after the long night. The hormone melatonin is a marker of nighttime physiology that helps regulate sleep and wake patterns. It has <a href="http://dx.doi.org/10.1016/j.smrv.2008.07.007">many important biological functions</a>, and its production requires dark but not sleep.</p>
<p>So whether awake or not, these subjects produced melatonin, and maintained nighttime physiology, for the long duration of dark. But this is not how people actually live in the modern world. People use electric lights and electronic gadgets in the evening, and often late into the night. </p>
<h2>The type of light we use at night matters</h2>
<p>A useful term in the context of sleep and health is “circadian effective light” because bright, short wavelength light (blue, for instance) is much more effective than dim, longer wavelength light (yellow/red) in <a href="https://theconversation.com/a-dark-night-is-good-for-your-health-39161">suppressing melatonin during the night</a> and causing a premature transition to daytime physiology. There is also <a href="http://dx.doi.org/10.1073/pnas.1418490112">evidence from studies in humans</a> that bright blue light in the evening decreases the quality of sleep compared to an evening of dimmer, longer wavelength light.</p>
<p>In industrial societies, people are bathed in blue light from smartphones, computers and some kinds of light bulbs all day, and for a good chunk of the night. Our preindustrial counterparts may stay up late too, but it’s in the dark or in the light of a flame.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/99368/original/image-20151022-8024-1fykk83.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/99368/original/image-20151022-8024-1fykk83.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/99368/original/image-20151022-8024-1fykk83.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=739&fit=crop&dpr=1 600w, https://images.theconversation.com/files/99368/original/image-20151022-8024-1fykk83.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=739&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/99368/original/image-20151022-8024-1fykk83.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=739&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/99368/original/image-20151022-8024-1fykk83.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=929&fit=crop&dpr=1 754w, https://images.theconversation.com/files/99368/original/image-20151022-8024-1fykk83.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=929&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/99368/original/image-20151022-8024-1fykk83.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=929&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Candlelight doesn’t interfere with our circadian rhythm like electric light. The Night School circa 1660-1665.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File%3ADou%2C_Gerard_-_The_Night_School_hi_res_-_c._1660.JPG">Gerrit Dou, via Wikimedia Commons</a></span>
</figcaption>
</figure>
<p>In the preindustrial time before electricity, sleep occurred within a much longer period of circadian dark; in the modern world it does not. Dark is restricted only to the sleep period, if even then; many people do not sleep in a truly dark bedroom. Seven hours of sleep embedded within 11 hours of circadian dark may be far more restorative than seven hours with bright, blue-containing light preceding it in the evening. The Siegel study might suggest that preindustrial people don’t sleep any more than people in industrialized societies, but perhaps they just get a better night’s sleep, and much more circadian dark. </p>
<p>For us in the industrialized world, it might be wise to use dimmer, longer wavelength lighting (like low wattage incandescent bulbs, if you can still find them) in the evening before sleep to allow an earlier transition to nighttime physiology. Fortunately, such circadian-friendly lighting is currently being designed with the new <a href="http://dx.doi.org/10.1002/adfm.201203209">lighting technologies now available</a>.</p>
<p>And during those inevitable periods of awakening in the middle of the night, try to enjoy the calm of darkness.</p><img src="https://counter.theconversation.com/content/49412/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Richard G. "Bugs" Stevens does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Is electricity making us sleep less? A new study on sleep in preindustrial societies suggests the answer is no. But it misses a big point: people in preindustrial societies spend more time in darkness than we do.Richard G. "Bugs" Stevens, Professor, School of Medicine, University of ConnecticutLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/250322014-04-06T20:08:41Z2014-04-06T20:08:41ZShould you be worried about getting enough vitamin D?<figure><img src="https://images.theconversation.com/files/45348/original/xkrzzghp-1396400962.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Many people struggle to balance the facts that too much sun exposure results in skin cancer and too little causes vitamin D deficiency. </span> <span class="attribution"><a class="source" href="https://www.flickr.com/photos/augustallen/2584362277">August Allen/Flickr</a>, <a class="license" href="http://creativecommons.org/licenses/by-nc-sa/4.0/">CC BY-NC-SA</a></span></figcaption></figure><p>With daylight saving ending yesterday across most of the country and winter approaching, Australians are moving from fears of too much sun exposure resulting in skin cancer to too little sun exposure and vitamin D deficiency. While the former concern may be justified, the evidence of the importance of vitamin D is less compelling. </p>
<p>The first part of this equation is not at all surprising: Australians worry about sun exposure because the country has the <a href="http://globocan.iarc.fr/Pages/summary_table_site_sel.aspx">highest skin cancer incidence in the world</a>. In 2012, 53.5 people in every 100,000 developed a melanoma. </p>
<p>The lead Australia holds on other countries is likely to be even higher for the less serious but more common non-melanoma skin cancers. There are no registry data for this disorder, but two in three Australians will develop at least one skin cancer by age 70.</p>
<p>So fears about too much sun exposure are justified but does the second part of the equation – vitamin D deficiency – matter? There are growing suspicions that this is not as important as we previously thought.</p>
<h2>The paradox of vitamin D</h2>
<p>In one of two papers about the vitamin published in the British Medical Journal (BMJ) last week, for instance, analysis of past studies linking vitamin D levels to an amazing 137 diseases <a href="http://www.bmj.com/content/348/bmj.g2035">failed to show convincing evidence</a> of a clear role for the vitamin, including in preventing falls and fractures. </p>
<p>The second paper looked at the <a href="http://www.bmj.com/content/348/bmj.g1903">extent to which vitamin D is associated</a> with death from heart disease, cancer and other illnesses. While it found low levels of vitamin D were linked to increased risk of premature death from disease, the authors urged caution about their results because the trials included only elderly people.</p>
<p>What both these summaries of research evidence show is that low vitamin D levels are associated with higher disease risk, but that vitamin D supplementation doesn’t actually decrease that risk. </p>
<p>Explanations for this apparent paradox include that the diseases themselves may be causing low vitamin D levels, or that low vitamin D levels are a marker of general poor health (such as not enough exercise or carrying excess weight), which increases the risk of developing disease.</p>
<h2>Fun in the sun</h2>
<p>In sunny Australia, we get most of our vitamin D through exposure of skin to the sun (in less sunny places vitamin D in food becomes important); and getting the right mix – enough sun exposure to make adequate vitamin D but not enough to get skin cancer – is a real source of confusion. </p>
<p>And confusion doesn’t just reign among people in the community, it can also prevail among doctors and researchers. For doctors, there are issues about whom to test for vitamin D deficiency, and how to treat them when the results come back. Should they advise sun exposure <em>or</em> vitamin D supplementation?</p>
<p>Vitamin D levels are a marker of recent sun exposure, so if you have low levels, you’ve probably not spent much time in the sun in the past few weeks. What we’re now starting to appreciate is that sun exposure itself may have beneficial effects on health that have nothing to do with vitamin D production.</p>
<p>Exposure to the blue part of visible light, for instance, may <a href="http://www.biomedcentral.com/1471-244X/11/17">prevent the development of the depression</a> that can occur in winter (seasonal affective disorder), which is associated with low light levels. In another example, more time outdoors seems likely to <a href="http://www.iovs.org/content/53/8/4363">reduce the risk of developing short sightedness</a> in childhood (myopia); probably again an effect of visible light, although the mechanisms are not yet clear. </p>
<p>Even the development of skin cancer is more complicated than sun exposure equals skin cancer. We know exposure to ultraviolet radiation causes DNA damage, which eventually leads to skin cancer, but that pathway also requires the immune system to be dampened down to allow the abnormal cells to form into a skin cancer. </p>
<p>And that same sort of immune suppression may <a href="http://www.ncbi.nlm.nih.gov/pubmed/21852793">decrease the risk of autoimmune diseases</a>, such as multiple sclerosis and type 1 diabetes. What’s more, exposure of the skin to ultraviolet radiation also causes <a href="http://www.nature.com/jid/journal/vaop/ncurrent/abs/jid201427a.html">release of chemicals other than vitamin D</a> that can decrease blood pressure. </p>
<h2>Baking and burning</h2>
<p>These recent findings make it even more difficult to work out how much sun you should get. In fact, levels of sun exposure may not be the main issue at all, it may be it’s pattern that’s key. </p>
<p>It makes sense that exposing <a href="http://www.ncbi.nlm.nih.gov/pubmed/24573539">more skin for a shorter time</a> decreases the harmful dose to any single cell but allows more vitamin D to be made. Of course, sunbathing to the point of getting sunburnt increases skin cancer risk.</p>
<p>Too much sun exposure can also break down the vitamin D already formed in the skin, so that’s clearly not an efficient way of making vitamin D – the harms greatly outweigh the benefits. </p>
<p>The challenge now is to develop a more nuanced message of sun exposure to reap benefits but minimise risks. We have a good understanding of these risks but are less certain about the full scope of benefits. And living in one of the most sun-affected countries in the world makes this a national priority.</p>
<p>New Australian research is addressing both the question of how to manage vitamin D deficiency (sun exposure or vitamin D supplements) and better defining both vitamin D and non-vitamin D effects of sun exposure on health (<a href="http://www.sedsstudy.org.au">click here</a> for more information or to participate). </p>
<p>We need to work out what to tell people – do we say “stay inside, avoid the sun completely and take vitamin D supplements”? Or, if sun exposure itself has good effects on health, we should say “a bit of sun exposure is good for you – but don’t bake and don’t burn”.</p><img src="https://counter.theconversation.com/content/25032/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Robyn Lucas receives funding from Cancer Australia and the National Health and Medical Research Council</span></em></p>With daylight saving ending yesterday across most of the country and winter approaching, Australians are moving from fears of too much sun exposure resulting in skin cancer to too little sun exposure and…Robyn Lucas, Associate Professor of Epidemiology, Australian National UniversityLicensed as Creative Commons – attribution, no derivatives.