Sleep tracking can show people how much sleep they are (or aren’t!) getting and the quality of that sleep. But how accurate are they? Can a wristband really tell you about your sleep patterns?
How Do Fitness Trackers Track Sleep?
The current best sleep test is
(PSG), which is performed by sleep clinics to diagnose sleeping disorders. You sleep a few nights at a clinic, hooked up to electrodes that measure your brain waves, heart rate, breathing, and eye/leg movements. Although this test is as accurate as it gets, it can be uncomfortable, time consuming, and expensive.
Enter the fitness trackers: a (comparatively) less expensive and more practical way to measure sleep in your natural environment. Fitness trackers use built-in accelerometers (which track your steps) to track how much you move at night in a process called “actigraphy”. The idea is to track how much time you spend moving (awake) or staying still (asleep).
How Accurate Is It?
As you can imagine, these aren’t perfectly accurate. Ever notice that your fitness tracker registers that you’re asleep even if you’re just lying in bed reading?
showed that the Fitbit overestimates the time adults spent asleep
by 67 minutes on average
demonstrated that the Jawbone UP overestimated the total sleep time/efficiency in adolescents.
What About Sleep Stages?
Some trackers claim they can track sleep stages, too.
Experts warn that buyers should be skeptical of this
. The most accurate way to measure sleep cycles is with a test called an electroencephalography (EEG), which measures brain waves during sleep. Brain waves differ between the various stages of sleep, as do eye movements and muscle tone. A wristband alone can’t measure all this.
Should I Trust My Tracker?
Although sleep trackers can’t always tell whether a user is awake if they’re still, some
suggest that sleep trackers are able to give
reasonably accurate measurements
of total sleep duration. When used over several days, a user can get a broad estimation of their sleep patterns to inform their sleep behaviors.
What’s the bottom line?
Sleep trackers overestimate quantity and quality of sleep, so they shouldn’t be used to identify sleep problems; however, they do provide insight into your day-to-day sleep patterns. If you feel like you’re having any sort of sleep issues, visit your doctor. But, if you’re looking for some general data on how well you’re sleeping, a fitness tracker can give you the kind of data you need (as long as you take it with a grain of salt).