Sleep
How Much Deep Sleep Do I Need?
Short answer
Most healthy adults spend roughly 13-23% of total sleep time in deep (slow-wave) sleep, which works out to about one to one and a half hours on a seven-to-eight hour night. Deep sleep declines naturally with age. Rather than chasing a wearable's deep-sleep minutes, the reliable route is to extend and stabilize total sleep — deep sleep largely takes care of itself.
What suppresses deep sleep
- Alcohol in the evening — it fragments the second half of the night and blunts slow-wave sleep.
- Late, large meals and late caffeine.
- High evening body temperature and a warm bedroom.
- Irregular bed and wake times, which desynchronize the circadian drive.
- Chronic short sleep: less total sleep means less of every stage.
What reliably increases it
- Consistent wake time seven days a week.
- Daytime aerobic exercise, finished several hours before bed.
- A cool, dark, quiet room.
- Morning daylight exposure to anchor the circadian rhythm.
A note on wearables
Consumer sleep-stage estimates are inferred from movement and heart-rate signals, not EEG. Use them for trends across weeks, not for judging a single night.
More answers
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