Medical Word - NREM-REM Sleep Cycle (synonymous with Sleep Cycle)
Ans : These cycles occur during sleep which starts with the first phase namely, NREM sleep episode and the second , which is the REM sleep episode. This NREM-REM phase constitutes one cycle with the duration of 90 minutes in adults. In a 6.5 - 8.5 hours of total sleep period of adults, there are nearly 4-6 cycles of NREM-REM sleep.