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Don’t call the doctor, your phone can now tell when you are stressed

Samsung S Health Stress

Samsung has just released an updated version of its health software for the Samsung Galaxy S5 that measures stress levels. Using the heart rate sensor on the back of the phone, the S5 will calculate a measure of stress from low to high.

Although this may seem far-fetched to some, the phone is actually using a measure of the heart rate to calculate something called “heart rate variability” or HRV. HRV has been shown to be related to a range of clinical conditions that include problems with the heart but also mental issues of stress and anxiety. Athletes have also used HRV as a measure of over-training and so use heart rate monitors to check if they need rest days.

So what is heart rate variability?

Most people don’t realise that even when a heart seems to be beating regularly, it is in fact affected by other factors, principally our breathing. The interval between beats shortens as we breath in (gets faster) and lengthens as we breath out (gets slower). The exact nature of this heart rate variability seems to be also under control of our autonomic nervous system and was first described in 1733 by the Rev. Stephen Hales.

By measuring the frequency at which the heartbeat varies, and doing some calculations on that data, a value can be obtained that is related amongst other things to levels of stress. The lower the HRV value, the higher the stress is. What that measure can’t tell you is what that stress is caused by. As mentioned before, if you are an athlete, it could indicate that you have over-trained and need a day off exercise. For people who aren’t exercising vigorously, it could mean that you are emotionally stressed.

Research has indicated that if you measure HRV continuously over a 24 hour period, you can detect differences between normal subjects and people having various mental disorders including panic attacks. To do this however, you would need to use a heart rate monitor that can measure and log data continuously.

The move to making wearable health devices

Samsung has gone a long way to incorporate sensors in its newest phone, the S5, and wearables like the Galaxy Gear 2 and the Galaxy Gear Fit. The sensors are actually pulse oximeters which work by shining red and infrared light on the finger and measuring the amount of light that is absorbed by blood in the finger. Apart from measuring heart rate, a pulse oximeter can measure the amount of oxygen in the blood, although it is not clear that Samsung is making use of that measure as yet.

The software that is doing all of the calculation obtained from these sensors in the S5 is probably from the Finnish company Firstbeat. Their website details that they are able to give a range of different physiological fitness indicators, not just the HRV that Samsung has decided to use in its health application S Health.

Will others follow?

Samsung seems to be claiming the ground in terms of innovation in health-related sensor technology. In addition to the built-in sensors, Samsung phones now support direct connections to heart rate straps using the Ant+ protocol as well as through Bluetooth.

There is evidence that Apple is working on health-related devices, but it has to be said that in this as in many things of late, it is definitely being a follower rather than a leader.