What is the normal NREM to REM cycle?

What is the normal NREM to REM cycle?

• A. 90-120 minutes
• B. 60-80 minutes
• C. 180 minutes
• D. 60 minutes

Answer: (A)

Normal sleep architecture unfolds in repeating cycles that begin with NREM sleep (stages N1–N3) and progress into REM sleep. Each cycle lasts about 90 minutes in adults, and across the night the REM portion tends to lengthen while deep NREM (N3) shortens. Because of natural individual variation, a typical NREM-to-REM cycle is in the range of roughly 90 to 120 minutes. That’s why the 90-120 minute range best describes the normal cycle. Shorter estimates around 60–80 minutes miss the full progression of a complete cycle, while 180 minutes is longer than usual for a single cycle.

Normal sleep architecture unfolds in repeating cycles that begin with NREM sleep (stages N1–N3) and progress into REM sleep. Each cycle lasts about 90 minutes in adults, and across the night the REM portion tends to lengthen while deep NREM (N3) shortens. Because of natural individual variation, a typical NREM-to-REM cycle is in the range of roughly 90 to 120 minutes. That’s why the 90-120 minute range best describes the normal cycle. Shorter estimates around 60–80 minutes miss the full progression of a complete cycle, while 180 minutes is longer than usual for a single cycle.