Sleep stages decoded in 5 fast facts

N1 is the lightest non-REM stage, a brief transition from wakefulness, often just a few minutes.
N2 is the stage with sleep spindles and K-complexes, often 10 to 25 minutes in the first cycle.
N3 is the deepest non-REM sleep, or slow-wave sleep, and is most concentrated early at night.
REM brings vivid dreaming, rapid eye movements, and temporary muscle atonia, usually starting about 90 minutes after sleep begins.
Micro-arousals are brief wake intrusions during sleep, commonly lasting about 3 to 15 seconds.

falling asleep and usually lasts one to seven minutes.

spend about half their sleep time in N2 sleep.

each N2 stage can become longer during the night.

eventually comprising about 45% of total sleep.

stage of sleep, and it\u2019s harder to wake someone up if they\u2019re in this phase.

these stages get shorter, and more time gets spent in REM sleep instead.

the eyes and diaphragmatic muscles, which remain active.

the final cycle lasting up to 1 hour.[21]

later stages can last for around an hour.

Sleep stages decoded in 5 fast facts

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