I’ve been tracking my sleep for quite some time now using the Apple Watch. I used to use the now-defunct Zeo Sleep Tracker, a device worn on the head using EEG signals to track your sleep. I’ve also ordered the Oura Ring, one of the more accurate consumer devices to track sleep.
Using the Apple Watch’s Sleep Watch app, I can only estimate my “restful sleep”. The app does not claim to know when you are in REM or deep sleep, very important sleep cycles. Hopefully, the Oura Ring can provide more insights into those cycles of sleep.
Although the iOS app doesn’t detect REM or deep sleep, I rely on it to detect my heart rate during sleep. A dip in heart rate during sleep is healthy and indicates more restful sleep. Studies correlate a lack of a heart rate dip with all-cause mortality, with findings state that “those with very small or no dips in sleeping heart rate were about 2½ times as likely to die in the next 7 years as those with normal or large dips during sleep”.1