Protocol
Evening warm bath or shower (40 to 42.5°C water)
(Sleep Med Rev, 2019; 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. 31102877) pooled 13 studies: water at 40 to 42.5°C for as little as 10 minutes, one to two hours before bed, went with faster sleep onset and better self-rated sleep.
Grade C: human trials exist, but they are small, mixed or not yet repeated. This is not a finding that it does not work. How to read a grade →
At a glance
A warm bath or shower an hour or two before bed raises body temperature, and the drop afterward may help sleep start. Small studies found people fell asleep a little faster after soaking in hot water for 10 minutes or more. A study of warm footbaths in older adults found no change.
Haghayegh et al. (Sleep Med Rev, 2019; PMID 31102877) pooled 13 studies: water at 40 to 42.5°C for as little as 10 minutes, one to two hours before bed, went with faster sleep onset and better self-rated sleep. The studies were small, and a warm footbath trial in 25 older adults found no change in measured or self-rated sleep (Liao et al., Int J Nurs Stud, 2013; PMID 23669188).
Why this letter
Why this gradeGrade C, small or unreplicated trials. The reasoning, and what the grade does not cover.
Grade C on sleep onset and sleep quality. Pooled small studies favored a warm bath or shower one to two hours before bed (Haghayegh et al., 2019; PMID 31102877), the supporting experiments held 6 to 9 people each (PMIDs 2578367, 3381061, 8736588), and the one randomized-order footbath trial was null (PMID 23669188).
WHY NOT Bno adequately sized randomized trial has repeated the pooled result.
WHAT THIS GRADE DOES NOT COVERsaunas, which have their own records; hot tubs and hot springs; baths taken right before lights out rather than one to two hours earlier; and insomnia as a diagnosed disorder, which the pooled studies mostly did not enroll.
A grade describes the human evidence for a named use. It is not advice, and it is not a judgment on any individual prescription. How the letters are decided →
Evidence notes: meta-analysis A study that pools the numbers from several trials into one combined estimate., 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.
Endpoint The outcome a trial measures to decide whether the treatment worked, such as heart attacks, blood pressure or a symptom score. graded: Sleep onset latency and sleep quality after a warm bath or shower one to two hours before bed (functional)
Last reviewed: October 2026
The trial that would change this grade.
A positive trial of this shape, supported by further trials, would move this entry to B.
Why the current trials fall short
The pooled studies are small single sessions. A trial of nightly use over weeks has not been run.
Why people believe itOne human source; no published case reports of benefit; no reports of harm.
The case for an evening bath is that sleep usually begins as body temperature falls, and warming the skin before bed speeds that fall.
What supporters point to, and what each source actually shows. None of it is enough to move this letter higher; the trial described above under Evidence wanted is what would.
- Human trial, blood or body markerIn 6 young women, a hot afternoon bath that raised core temperature by 1.8°C was followed by more deep sleep that night. PMID 2578367
A case report describes what happened to one or a few patients. It cannot show the treatment caused the change, and reports of success are published more often than reports of failure.
A PubMed search in October 2026 found no published case report of benefit for this use.
Searched PubMed, October 2026: 8 case report record(s) returned. None describes a bath taken for sleep. The records concern sauna burns, cardiac events and unrelated conditions.
Dose, form and timing
Sleep onset latency and wake after sleep onset on a sleep diary or wearable for two weeks with and two weeks without the bath.
As studiedDose, form, population and duration for every use.
A grade describes the intervention that was tested. Where the product on the shelf differs from it, this says so.
Grade history
How this letter has changedLatest: No. 368 · October 2026 · First graded.
An evening bath or shower now has a record. Pooled small studies found faster sleep onset with water at 40 to 42.5°C one to two hours before bed (Haghayegh et al., Sleep Med Rev, 2019; PMID 31102877), and a footbath trial found no change (Liao et al., Int J Nurs Stud, 2013; PMID 23669188). Grade C.PMID 31102877 PMID 23669188
Every change to a letter on this site is dated and published. The full evidence log →
Sources
- Citations
- Every paper cited on this page is matched to its PubMed record on every build.
- Retractions
- None of these papers is retracted or under a journal expression of concern. PubMed is checked again on every build.
- Read against the papers
- October 2026. By a language model (AI-assisted reading), not yet reviewed by a clinician.
- Outside review
- Not yet done. No reviewer outside EBL has checked this record.
What each of these checks can and cannot show: evidence integrity.
The evidence, in fullFive papers, each linked to its PubMed record.
Haghayegh et al. (Sleep Med Rev, 2019; PMID 31102877): systematic review A review that searches for every study on a question using a method set in advance, then assesses them together. of 17 studies, 13 pooled; the authors describe the evidence as scarce. Horne and Reid (Electroencephalogr Clin Neurophysiol, 1985; PMID 2578367): 6 women, deep sleep rose after a hot bath. Bunnell et al. (Sleep, 1988; PMID 3381061): deep sleep rose only after evening immersion. Dorsey et al. (J Geriatr Psychiatry Neurol, 1996; PMID 8736588): 9 older women with insomnia, better sleep continuity after hot baths. Liao et al. (Int J Nurs Stud, 2013; PMID 23669188): randomized-order 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., 25 older adults, a 40°C footbath changed neither polysomnography nor self-rated sleep.
How EBL searched for the trials (1 search)
The search that was run, what it returned, and what was left out and why, so the absence of evidence can be checked as well as its presence.
("warm bath"[tiab] OR "hot bath"[tiab] OR "warm shower"[tiab] OR "passive body heating"[tiab] OR footbath[tiab]) AND sleep[tiab]Disclosure
Educational use only · Not medical advice · EBL grades published human evidence and does not recommend treatment. Stopping a prescription is a decision for your physician.
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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These statements have not been evaluated by the Food and Drug Administration. Any grade on this page describes the strength of published human trial evidence in the populations studied. It is not a recommendation for any individual and is not medical advice. Starting, stopping or changing any supplement or medication is a decision for your physician.
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