How do activity trackers know when I’m asleep? How they deduce REM sleep, deep sleep etc?
In: Technology
Mainly the combination of no motion and heart rate variability. Everyone will have slightly different heart rates at sleep, the question is what is the difference between sitting very still and relaxed and being asleep. The answer is heart rate variability, and it isn’t an exact measure. For example, I have been awake watching TV and my Garmin thought I was asleep. Sleep studies do similar things but also listen for snoring and read your blood oxygen level. That is still essentially a guess as someone has to actually listen to you the recording to make sure you were actually asleep.
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