Sleep hygiene — 8 research-backed rules (and 3 myths)

"Sleep 8 hours" is the world's most common and least practical advice. Sleep research (summarised e.g. in Irish et al., 2015) shows that sleep quality depends on a handful of concrete, modifiable habits — and that some popular tips are myths.

8 rules that work

1. A fixed schedule — weekends included. The circadian rhythm loves predictability; Saturday lie-ins act like a mini jet lag.
2. Daylight before noon. 15–30 minutes outside anchors the body clock more strongly than any evening supplement.
3. Bedroom: dark, quiet, cool. Around 18–19°C is optimal for most people.
4. Caffeine has a ~5-hour half-life. A 4 p.m. coffee is still a quarter dose at midnight.
5. Screens leave an hour before sleep. It is not just blue light — it is the arousal from content.
6. Daytime movement shortens sleep onset and deepens slow-wave sleep.
7. A wind-down ritual — a repeatable sequence (shower, stretching, reading) teaches the brain that sleep is coming.
8. Can't sleep after 20 minutes? Get up. Return only when sleepy — the bed should be associated with sleep, not frustration.

3 myths

"Alcohol helps you sleep" — it speeds up falling asleep but fragments the second half of the night and suppresses REM. "A nap is always a good idea" — beyond 30 minutes or after 3 p.m. it eats the evening's sleep pressure. "Older people only need 5 hours" — sleep need declines only slightly with age; the ability to maintain sleep declines more.

Where to start

Not with everything at once. The sleep hygiene test shows which habits sabotage you most — fixing two or three is usually enough to feel a difference within two weeks.