Sleeping Process

Sleep trackers

Nowadays wearable sleep trackers are nearly ubiquitous in our modern society. Think about it: Fitbit, Polar, Oura ring, Garmin, WHOOP, Beddit, SleepWatch, …  Knowing these self-tracking sleep devices, having one of these or friends having one of these, confirm the fact of a tremendous increase of sleep awareness over the last decade. As a result of this explosion, sleep clinicians are flooded with questions concerning bad sleep according to the sleep trackers. Yet, plenty of these self-tracking sleep wearables lack accuracy, reliability and usability. Therefore, they hold the risk of misinforming you and biasing your perceptions regarding your sleep health. Although there are some potential benefits in terms of measurement if the data are interpreted and used for non-clinical purposes, like detecting improvements of sleep hygiene alterations.

When it comes to properly quantifying your sleep, polysomnography (PSG) is still the most reliable and accurate measure. PSG quantifies your brain, muscle and eye activity during sleep in order to classify your sleep and sleep stages in particular. Because PSG is performed in sleep laboratories due to the requirement of the expensive specialized equipment and skilled technicians to conduct the overnight procedure, it is not a viable candidate for a wearable metric of sleep. Nonetheless, it is the gold standard against which any other device purporting to measure sleep should be assessed. The issue is: only a subset of the commercially available self-tracking sleep wearables has been tested for accuracy and reliability against this gold standard. Most consumer wearable devices are not approved and are therefore categorized as “wellness” products.

It is apparent by scientific research that all these devices:

  1. overestimate deep sleep time,
  2. overestimate REM sleep time,
  3. underestimate the time spent in light sleep,
  4. underestimate the total time the user is awake,
  5. overestimate the total time the user is asleep, and
  6. do not take into account certain factors such as alcohol consumption that affect your sleep as well.

Thus, currently, these sleep technologies conduct a remarkably poor inaccuracy in staging sleep. We can conclude that there is a lack of accessible and objective tools for quantifying sleep outside of laboratory clinical settings. Therefore, we do not recommend that these sleep staging metrics are incorporated into any decision-making when it comes to clinical self-monitoring your sleep at this time. But this does not mean that you should throw out your sleep tracker. It is important to understand the intent of utilizing your sleep device. It can be enlightening and potentially utilized as an augmentation tool for bettering your health. For example, improving your sleep behaviors based on the simple sleep hygiene tips, such as going to bed more consistently to increase of your total sleep time, can accurately be assessed by these technologies. It is even recommended because it is interesting for you to see the impact of these changes on your sleep patterns

So, as long as you don’t any draw clinical conclusions based on the absolute numbers (e.g. the amount of REM-sleep) stated by your device, it is absolutely okay to use it. If you think you are seriously experiencing sleeping troubles (see previous part concerning sleep disorders), we advise you to see your doctor. A PSG is only used to investigate a potential sleep disorder in a patient.


Stone, J. D., Rentz, L. E., Forsey, J., Ramadan, J., Markwald, R. R., Finomore, V. S., Galster, S. M., Rezai, A., & Hagen, J. A. (2020). Evaluations of Commercial Sleep Technologies for Objective Monitoring During Routine Sleeping Conditions. Nature and science of sleep, 12, 821–842.

Depner, C. M., Cheng, P. C., Devine, J. K., Khosla, S., de Zambotti, M., Robillard, R., Vakulin, A., & Drummond, S. (2020). Wearable technologies for developing sleep and circadian biomarkers: a summary of workshop discussions. Sleep43(2), zsz254.

de Zambotti, M., Rosas, L., Colrain, I. M., & Baker, F. C. (2019). The Sleep of the Ring: Comparison of the ŌURA Sleep Tracker Against Polysomnography. Behavioral sleep medicine, 17(2), 124–136.

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