Sources & how to read the evidence

This guide was built from the primary literature — clinical guidelines, randomised trials, meta-analyses, and validation studies — and graded by how strong the evidence actually is. Sleep is a field thick with gadgets and overstated books, so where a claim is thin or a product is hyped, it says so and shows both sides.

How it was built

The approach: Every load-bearing claim comes from a named guideline, trial, meta-analysis, or validation study, with the evidence dots (●●●●● = strong and replicated, down to ○○○○○ = essentially unproven) reflecting study design, size, and replication. Figures are group averages; individuals vary widely. This is educational, not a diagnosis or a prescription — and where a popular book (like Why We Sleep) overstates a scary number, the guide uses the underlying literature instead.
The key sources: Foundations & metrics: the AASM/Sleep Research Society duration consensus, the Sleep Regularity Index mortality studies, and Van Dongen's sleep-debt work. Environment: the Zeitzer, Chang & Mason-Zee light studies, the Haghayegh warm-bath meta-analysis, the Drake caffeine study, and the Stutz exercise-timing meta-analysis. Tracking: the Chinoy multi-device validation and the orthosomnia literature. Breathing: the AASM apnea guideline, WatchPAT validation, SURMOUNT-OSA (tirzepatide), and the mouth-taping safety review. Supplements & drugs: the AASM pharmacologic guideline, the low-dose-melatonin work and the melatonin-quality analyses, and the DORA/doxepin trials. Jet lag & mind: the Cochrane melatonin jet-lag review, the creatine sleep-deprivation study (graded as early), the ACP recommendation of CBT-I as first-line, and the Balban breathwork trial. The frontier: the Ngo and Papalambros closed-loop pink-noise work, the Elemind trial, the Ekholm weighted-blanket RCT, and the bedroom-CO₂ study.

Educational reference — not medical advice

This guide summarises published research for general education. It is not a diagnosis, a prescription, or a substitute for care. Get red-flag symptoms assessed — loud snoring with witnessed pauses, gasping, severe daytime sleepiness, or a sudden change in your sleep — and never start, stop, or change any medication on your own. Decide anything here, especially anything involving a drug or a suspected sleep disorder, with a qualified clinician.

The Sleep Guide