Can We Trust Smartwatch Data That Tracks Sleep Stages?
I recently bought a new smartwatch, and it breaks down sleep stages in detail. Times for falling asleep and waking up seem roughly right, but I'm curious how on earth it distinguishes things like 45 minutes of REM and 1 hour of deep sleep.
If there are any doctors or people who study biosignals out there... isn't there a limit to determining sleep stages just from heart rate changes? Or is this level of data meaningful enough to be worth paying attention to?
Personally, I'm satisfied as long as I hit 7 hours a day. Just for the fun of checking it with my own eyes.
3 answers
Haha, I also just look at it for fun.
I've always known that it roughly calculates based on your heart rate and tossing/turning patterns while sleeping, so it's never perfectly accurate. Still, for getting a big-picture sense of how much sleep you're averaging, I think it works fine. I've been using it for a few years now... At first, I used to get all excited or disappointed every morning looking at the sleep stages, but now I just check the total sleep time lol.
I'm not an expert, but as someone who has studied biosignals, using only heart rate to distinguish sleep stages is really just a rough estimate. Especially for REM, you need EMG or EEG to be accurate, and wrist movement or heart rate variability gives low accuracy. Doctors also only use it as a reference, not for diagnosis, so don't trust it too much. Still, maintaining 7 hours is a good habit.