N1 sleep is the lightest phase, what most people call napping. It lasts less than ten minutes.
N2 sleep is what I've known as delta-wave sleep. It lasts 30-60 minutes. The combination of N1 and N2 is what is conventionally evoked in a twenty minute "power nap."
N3 sleep is the deepest phase of non-REM sleep, lasting 20-40 minutes. Waking someone from this phase is VERY difficult. Ironically, THIS is the phase where night terrors occur, and the difficulty waking someone is definitely part of the problem.
REM sleep is when dreaming happens. It can take anywhere from an hour to two hours to even GET to REM sleep, so the popular advice for "90 minute sleep cycles' is BUNK.
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dancing_serpent
A detail
Date: 2025-07-02 02:04 pm (UTC)N2 sleep is what I've known as delta-wave sleep. It lasts 30-60 minutes. The combination of N1 and N2 is what is conventionally evoked in a twenty minute "power nap."
N3 sleep is the deepest phase of non-REM sleep, lasting 20-40 minutes. Waking someone from this phase is VERY difficult. Ironically, THIS is the phase where night terrors occur, and the difficulty waking someone is definitely part of the problem.
REM sleep is when dreaming happens. It can take anywhere from an hour to two hours to even GET to REM sleep, so the popular advice for "90 minute sleep cycles' is BUNK.