NREM sleep, or non-rapid eye movement sleep, is a phase of sleep without dreams. During this stage, EEG recordings show slow, high-voltage brain waves. Breathing and heart rate are steady and slow, blood pressure is reduced, and the person remains mostly motionless. NREM sleep progresses through four stages, each becoming progressively deeper.In contrast, REM sleep is when dreaming happens. Throughout a night, we typically experience 3 to 5 REM cycles, occurring every 1-2 hours. These periods vary in length, lasting anywhere from 5 minutes to over an hour. REM sleep is marked by rapid, low-voltage brain waves, irregular breathing and heart rates, and occasional muscle twitches.Approximately 80% of our sleep is spent in NREM sleep. So, if you sleep for 7-8 hours a night, nearly all but about an hour and a half is dreamless NREM sleep.

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