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Health Area: Sleep

Sleep depends on enough hours, a regular schedule and a body clock set by light. When sleep problems persist, it is worth checking for two common conditions with established treatments: insomnia and obstructive sleep apnea.

Why it matters

Most sleep advice is a list of tips. Our topics point to a different order: first check for insomnia or sleep apnea, which have treatments with strong evidence, then work on the habits that are cheap to change. Caffeine and alcohol matter more than many people notice, and how much caffeine affects your sleep depends on the dose and the timing.

Key insights from this synthesis

  • For insomnia that lasts for months, the recommended treatment is a structured programme called CBT-I, not more sleep tips. On their own, sleep hygiene tips are not recommended as a treatment.
  • Sleep apnea is common and often missed, and it does not always look like snoring. Treatment reliably reduces daytime sleepiness; it has not been shown to prevent heart attacks or strokes.
  • The practical habits are about timing: a consistent wake-up time, with enough time for the sleep you need, and daylight in the morning.
  • Caffeine and alcohol can affect sleep more than you notice. The later and larger the caffeine dose, the more it reduced sleep in controlled studies.

Draws evidence from 19 expert discussions across 2 topics — 8% of our analysed library.

Synthesised 2026-10-08

How firmly is each conclusion stated?

Conclusionson this page
  • · What sleep depends on
  • · What sleep depends on
  • · What gets in the way
  • · What gets in the way
  • · What gets in the way
  • · What helps most
  • · What helps most
  • · What helps most

Each segment represents one conclusion. Its colour shows how firmly our topics state it, not how certain the science is. Read the full explanations in How confident can we be?

What may help?Practical steps for better sleep, and when to seek treatment.
How confident can we be?See what the evidence supports, and where confidence is weaker.
Firmly statedPartly supported

Light is the main signal that sets the body clock. Daylight in the morning and dimmer light in the evening support it; how bright the light is and when you see it matter, not only its blue part. Specific amounts of light are expert rules of thumb.

Sleep & Circadian Rhythm

Methodology & sources

Library reach

This Health Area draws evidence from 2 topics, 19 expert discussions and 1,361 minutes of expert conversation — 8% of the 244 discussions analysed so far.

This describes how much of our library contributes to this page. It is not a claim about how much of human health this subject accounts for.

About the sources

This page combines findings from 2 topics. Each topic is itself synthesised from expert discussions, and every finding links back to the topics that support it. Where topics disagree, or the evidence is limited, that is shown rather than hidden.

Topics (2)

Most influential here

The topics the most findings on this page draw on — a measure of this synthesis, not a ranking of the topics themselves.

Expert discussions (19)

1,361 minutes of expert conversation across the topics above.

Showing 10 of 19
What this page cannot yet tell you
  • Sleeping pills, antihistamines and other sleep aids: their risks, their benefits, and how they compare with CBT-I.
  • Melatonin dosing: the doses mentioned are expert statements we have not checked.
  • Shift work, menopause, teenagers, older adults, naps and restless legs.
  • Caffeine beyond its effect on sleep rests on one episode.
  • None of our sources is a psychiatrist or a pharmacologist.

Last synthesised 2026-10-08

What can we get wrong, what is contested, and what is changing?Common mistakes, expert disagreements, emerging evidence and important context.

Where experts diverge

Experts disagree on several key points. Each entry shows the mainstream view, the contested view, and what guidance survives both.