The latest statistics from Pew Research Center suggest that around 7 in 10 adults in the U.S. track at least one health 'indicator', such as sleep (Fox and Duggan, 2012).
Half of this group monitor their health, simply by keeping track in their heads, but 1 in 5 use some form of technology to do so. This might include anything from a simple spread sheet on your computer, to mobile phone apps and tracking devices such as Jawbone's UP band or BodyMedia's FIT band.
As the technology which drives these apps continues to advance, and access to smartphones rapidly increases, it is likely that very soon our personal devices will automatically track the steps we take, the calories we burn and the time we spend sleeping.
Android and iPhone sleep apps
Modern smartphones include devices called 'accelerometers', which measure movement. These are used, for example, to detect the phone's orientation to switch the screen between 'portrait' and 'landscape' modes.
Sleep recording apps use this same technology to monitor your movement throughout the night, gathering information about how long you slept and how many times you woke up, based on how much you moved.
Many sleep apps also feature a 'smart alarm'. Most often, these are intended to wake you up within a window of 'lighter' sleep, in order to minimize 'sleep inertia', the period after waking in which you may feel groggy and disorientated as you transition into wakefulness.
It is important to note however, that there are many factors that can affect how you feel on waking, and that the majority of mobile phone sleep apps have little to no clinical evidence behind them.
Wearable devices with sleep tracking
There is a wide range of wearable self-tracking devices available, many of which offer sleep tracking.
The devices are usually worn on your wrist or attached to clothing, and sync with mobile and/or web-based applications, which allow you to view the data these devices collect.
The majority of wearable devices use accelerometers, similar to those used in mobile phones, to track movement. Some also feature additional technology to track factors such as temperature, heart rate and skin conductance (galvanic skin response).
Traditional sleep monitoring
Sleep monitoring is usually carried out by experienced technicians, in sleep laboratories or sleep centers. A number of physiological parameters are assessed in this laboratory context.
Electrical activity in the brain is measured by electroencephalography (EEG), which is used to differentiate between wakefulness, sleep, and different stages of sleep.
Muscle activity is measured using electromyography (EMG), because muscle tone also differs between wakefulness and sleep.
Lastly, eye movements during sleep are measured using electro-oculography (EOG). This is a very specific measurement that helps to identify Rapid Eye Movement or REM sleep, during which we often dream.
This multi-assessment protocol is usually called polysomnography (PSG), and it remains the only clinically reliable sleep tracking tool. Despite this, the simpler tracking offered by devices and sleep recording apps can still help give people a better understanding of their sleep.
A recent study even suggested that some sleep tracking devices, which have the ability to record electrical brain activity relatively unobtrusively, may be “an accurate complement” to existing sleep measuring apparatus, such as the polysomnogram (Shambroom et al., 2012).
Fox, S. & Duggan, M. (2012). Report: tracking for health. Pew Research Center. http://www.pewinternet.org/Reports/2013/Tracking-for-Health.aspx
Shambroom, J.R., Fabregas, S.E., Johnstone, J. (2012). Validation of an automated wireless system to monitor sleep in healthy adults. Journal of Sleep Research, 21(2), 221-230.