Explainer
Why your sleep tracker is probably wrong
Wearables are good at measuring how long you sleep. They are much worse at telling you how well.
Health reporter
5 min read
Consumer sleep trackers estimate sleep stages from movement and heart rate.
Your watch says you had 47 minutes of deep sleep. The honest answer is: probably, give or take a lot.
Here is what sleep trackers measure well, what they guess, and when to ignore them.
What they get right
Total sleep time and regularity. Most trackers are within 10 to 15 minutes of lab measurements.
What they guess
Sleep stages. Laboratories use brain activity; wrist devices use movement and heart rate, which are indirect signals.
When to ignore them
If checking your score makes you anxious, sleep researchers suggest taking the watch off. The condition even has a name: orthosomnia.
Topics
Hannah Okoye
Health reporter
Hannah covers health systems, patients and what actually happens in waiting rooms.
