Sleep Trackers Reviewed

One of our patients recommended that we look at a YouTube video that summarized the scientific literature on fitness watches and rings as sleep trackers.

We think that it is a pretty good place to start if you are considering buying a device and sleep is an important part of what you want to track.

Before diving into the details, one issue to consider is, do you have reason to believe that you have a significant sleep disorder, such as obstructive sleep apnea or periodic limb movements of sleep? If so, you should note that almost all of the devices did a poorer job measuring sleep in people with sleep disorders.

A comprehensive analysis of sleep trackers was conducted based on available scientific publications by a researcher who also creates YouTube videos. This spreadsheet includes all of the data.

• Garmin devices demonstrated high sensitivity, meaning they were able to accurately detect sleep episodes. However, their low specificity resulted in false positives, where wakefulness was misidentified as sleep. This could lead to an overestimation of sleep duration.

• Polar devices exhibited a trade-off between sensitivity and specificity. While they were able to accurately detect sleep and wakefulness, their performance was not as consistent as other brands.

• Fitbit devices outperformed Garmin and Polar overall, displaying higher sensitivity and specificity in detecting sleep and wakefulness. This makes Fitbit a reasonable and relatively inexpensive option for individuals looking for accurate sleep tracking. Note that there was a significant trend in the Fitbit data suggesting that Fitbit (and now Google) watches were improving quickly in an effort to catch up with Apple.

• Whoop devices prioritized specificity over sensitivity. While they were effective in distinguishing sleep from wakefulness, they might have missed some sleep episodes, resulting in an underestimation of sleep duration.

• Oura Ring Generation 3 showed significant improvements in sleep and wakefulness detection compared to previous generations. Its enhanced accuracy made it a top performer in this category.

• Apple Watch Series 8 (and all subsequent watches) were the best performers in sleep stage tracking and in distinguishing sleep and wakefulness. It demonstrated the ability to accurately identify different sleep stages, divided into light, deep, and REM sleep.

Polar and Garmin devices exhibited poor sleep stage tracking performance. Their inability to accurately distinguish between different sleep stages limits their usefulness for individuals interested in detailed sleep analysis.

Xiaomi’s Mi Band 7 was the worst performer in sleep stage tracking. Its limited capabilities make it less suitable for individuals seeking comprehensive sleep insights.

Sleep tracking results were much poorer when used by individuals with sleep disorders. All top brands showed decreased performance, highlighting this population’s sleep-tracking challenges. As of the publication of this survey, none of the devices would be very accurate for those with sleep disorders except perhaps the most recent Apple watches. This finding underscores the need for further research and development to improve sleep tracking accuracy for individuals with sleep disorders.