REM sleep is the sleep stage marked by rapid eye movements (REMs). Throughout the night, we experience 3 to 5 REM sleep periods, occurring every 1-2 hours and varying in duration from 5 minutes to over an hour. Approximately 20% of our sleep is spent in REM sleep, so if you sleep 7-8 hours, around 90 minutes is likely REM sleep. This phase is also characterized by rapid, low-voltage brain waves seen in EEG recordings, along with irregular breathing, heart rate, and muscle twitches.In contrast, NREM (non-REM) sleep is a dreamless state. During NREM sleep, EEG brain waves are typically slow and high-voltage, breathing and heart rate are steady and slow, blood pressure is low, and the sleeper remains relatively still. NREM sleep is divided into four stages, each deeper than the last, eventually leading to REM sleep. About 80% of sleep is spent in NREM, which means if you sleep for 7-8 hours, nearly all but an hour and a half is in this dreamless state.

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