The basics, ranked by how much they matter
High impact
- Consistent wake time. The single most useful item. A fixed wake time anchors the circadian system far more effectively than a fixed bedtime, because light exposure after waking is the strongest entraining signal available.
- Morning daylight. Ten to twenty minutes of outdoor light within an hour of waking. Indoor lighting is roughly one to two orders of magnitude dimmer and much weaker as a signal.
- Caffeine timing. Caffeine has a half-life of about five to six hours, so an afternoon coffee still has meaningful levels at bedtime. Sensitivity varies genetically; some people tolerate an afternoon cup, many do not.
Moderate impact
- Temperature. Core body temperature needs to drop to initiate sleep. A cool room (roughly 16–19°C for most people) plus warm extremities helps. See best sleeping temperature.
- Alcohol. Shortens sleep onset, suppresses REM early in the night, and causes rebound arousal as it clears — which is why a nightcap reliably produces a 3am wake-up.
- Late heavy meals. Digestion raises core temperature. Timing matters more than content for most people.
Lower impact than the internet suggests
- Screen blue light. The effect is real but modest. The more important variable is what you are doing on the screen: an arousing email or a competitive game matters far more than the wavelength.
- Mattress and pillow upgrades. Worth doing if yours is genuinely uncomfortable; rarely the cause of chronic insomnia.
- Supplements. See melatonin and magnesium for what the evidence actually supports.
Why sleep hygiene is not a treatment for insomnia
Sleep hygiene assumes the problem is habits that were never learned. Chronic insomnia is usually a system that has learned the wrong thing: bed now predicts wakefulness, and the effort to sleep produces the arousal that blocks it. Changing room temperature does not unlearn that. The techniques that do are stimulus control and sleep restriction, both from CBT-I.
Sleep hygiene is best understood as the floor: get it right so nothing is actively working against you, then do the real work.
A practical baseline
- Fixed wake time, seven days a week.
- Daylight within an hour of waking.
- No caffeine after 12pm until you know your own tolerance.
- No alcohol within four hours of bed.
- Cool, dark, quiet room.
- Screens down 30–60 minutes before bed, and nothing arousing after that.
- Bed for sleep and sex only.
If you do all of this for three weeks and still cannot sleep, the problem is not hygiene.