Buzz
How many times have you woken up feeling fine, only to check your phone and see your sleep was labeled as 'low quality' or that you barely got any 'deep' sleep? Did you feel terrible the rest of the day? It’s possible your tracker, not your actual sleep, is partly to blame for how you felt.
The reality is that sleep trackers are decent at identifying when you slept—they can easily detect your bedtime and wake-up time—but they struggle to accurately assess what happens during your sleep. Everyone’s sleep needs vary, so even if you didn’t get the eight hours you aimed for, it doesn’t necessarily mean something is wrong.
In a 2014 study (paywalled but summarized here), researchers asked participants about their perceived sleep quality and then presented them with lab-based sleep data. They misled participants about their sleep: some were told they had above-average REM sleep, while others were told they had below-average REM sleep.
During a series of cognitive tests, participants’ performance often aligned with how well they were informed they had slept, though not always. It appears they trusted the fabricated analysis more than their own feelings and experiences.
Fitness trackers feel incredibly personal and reliable. We receive real-time data and have little reason to doubt it. However, in a 2017 study, sleep experts noted that trackers were disrupting some patients’ treatments. (One woman, for instance, had normal lab sleep results but questioned how that was possible when her Fitbit claimed her sleep was poor.) The authors stated:
All three patients were spending too much time in bed trying to increase the sleep duration reported by their trackers, potentially worsening their insomnia. Since these devices often overestimate sleep, they might encourage unhealthy sleep habits by promoting extended time in bed.
There’s no data on how often people might be misled about their sleep quality based on tracker feedback. It could be rare, or it might happen more frequently than we realize. The key takeaway is that your sleep tracker isn’t always accurate. Rely on your body and instincts rather than outsourcing that trust to technology. If a sleep expert advises something that contradicts your app, it’s wise to follow the professional’s guidance over the app’s.
