Sleep Runs in Cycles of About Ninety Minutes
Sleep is the natural state of reduced consciousness. It is not uniform but moves through repeating stages all night.
Sleep is the natural recurring state in which consciousness is suspended and the body rests. It is not one continuous condition: sleep runs in cycles of roughly ninety minutes, moving from light sleep through deep slow-wave sleep and into REM, when most vivid dreaming happens and the body is temporarily paralysed. Deep sleep dominates the early cycles, REM the later ones, which is why the last hours before waking hold the most dreaming. *Sleep on it* is old advice with some evidence behind it, since sleep helps consolidate memory.
- Natural rest. *A good night's sleep.*
- REM sleep — the dreaming stage. *REM sleep.*
- Slow-wave sleep — deep sleep. *Deep sleep.*
- Sleep on it — decide tomorrow. *Sleep on it.*
- Old English — *slæp*. *The source.*
Word forms
| Form | Word | Example |
|---|---|---|
| Noun | sleep | Deep sleep. |
| Verb | sleep | Sleep well. |
| Past | slept | Slept. |
| Adjective | sleepy | Sleepy. |
| Adjective | asleep | Asleep. |
- She had eight hours of sleep.Rest.
- Cycles last about ninety minutes.Science.
- Let me sleep on it.Idiom.
The stages of a sleep cycle
- N1 — the brief drift into sleep
- N2 — light sleep, the largest share of the night
- N3 — deep slow-wave sleep, hardest to wake from
- REM — rapid eye movement, vivid dreams, muscles paralysed
- Each cycle lasts about ninety minutes and repeats four to six times
Old English *slæp*, of Germanic origin, related to Dutch *slaap* and German *Schlaf*.
Why do we dream most before waking?
Because REM sleep takes a larger share of each later cycle, so the final hours before waking contain the most dreaming.
Does sleeping on a decision help?
There is evidence that sleep aids memory consolidation and problem solving, so the old advice has some support.