The deep stages of NREM sleep do not differ significantly from REM sleep in terms of the level of body movement since both types of sleep are characterized by heavy muscle paralysis. To distinguish REM sleep from the deep sleep phases which precede it, one would need to check for the presence of random eye movement using electrooculography(EOG). Unfortunately, we are not able to accomplish this using the current technology of smartphones.
Why doesn’t Sleep Time distinguish between Deep and REM sleep?
