Protocol · not graded
Caffeine timing before sleep
How long before bed caffeine was taken, and what it did to sleep measured at home.
At a glance
This page is about how long before bed caffeine was taken and what it did to sleep. In one small trial, 12 healthy adults took a large dose of caffeine, about four cups of coffee, at bedtime, 3 hours before or 6 hours before. Even 6 hours before bed, it cut sleep by more than an hour. No trial has tested a cutoff time.
One small trial found 400 mg of caffeine 6 hours before bed still shortened measured sleep; not graded.
Why this letter
Not graded. One small randomized crossover A trial design in which each participant receives both the treatment and the comparison, one after the other, and serves as their own control. trial tested one 400 mg dose at three times before bed; no trial has tested a cutoff time against a health outcome.
Evidence notes: randomized trial, not independently replicated The same finding reproduced by a separate research group. A result seen once can be chance or bias; a replicated one is harder to explain away.
Last reviewed: October 2026
Dose, form and timing
No outcome target is established.
Grade history
How this letter has changedLatest: No. 351 · October 2026 · Corrected.
The nutrition page's caffeine entry had no citation. It now cites Drake et al. (J Clin Sleep Med, 2013; PMID PubMed ID: the permanent number the US National Library of Medicine gives a published paper. Each one links to that paper's record on PubMed. 24235903), a randomized crossover trial in 12 healthy adults in which 400 mg of caffeine taken even 6 hours before bed shortened measured sleep by more than an hour. One small trial of one dose carries no letter.PMID 24235903
Every change to a letter on this site is dated and published. The full evidence log →
Sources
The evidence, in fullOne paper, linked to its PubMed record.
Drake et al. (J Clin Sleep Med, 2013; PMID 24235903): randomized, double-blind Neither the participants nor the people assessing them know who received the real treatment until the trial ends., placebo-controlled crossover trial in 12 healthy normal sleepers. 400 mg of caffeine or placebo An inactive substitute made to look like the real treatment, so participants cannot tell which one they received. was taken at bedtime, 3 hours before and 6 hours before, with sleep measured at home. Caffeine at every time point disrupted sleep, and even 6 hours before bed it reduced total sleep time by more than an hour.
Disclosure
Educational use only · Not medical advice · EBL grades published human evidence and does not recommend treatment.
Evidence Based Longevity, Inc. is owner-operated and edited by Arnold Sandlow, D.C., a California-licensed chiropractor. Evidence Based Longevity publishes in English only · Machine translations are not produced or reviewed by EBL for accuracy
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