Before-bedtime passive body heating by warm shower or bath to improve sleep: A systematic review and meta-analysis.
Level 1 - systematic review of randomized trials
Systematic review and meta-analysis of intervention studies
PubMed 31102877 · doi:10.1016/j.smrv.2019.04.008
What was done
The authors conducted a systematic search across six databases (PubMed, CINAHL, Cochrane, Medline, PsycInfo, and Web of Science) to evaluate the effects of water-based passive body heating (warm shower or bath) before bedtime on sleep onset latency, wake after sleep onset, total sleep time, sleep efficiency, slow wave sleep, and subjective sleep quality. From 5,322 candidate articles, 17 met predefined inclusion criteria, and 13 provided comparable quantitative data for meta-analyses.
What was found
Passive body heating with water at 40–42.5 °C was associated with improved subjective sleep quality and sleep efficiency. When scheduled 1–2 hours before bedtime for as little as 10 minutes, it significantly shortened sleep onset latency. The abstract reported no exact effect sizes, point estimates, or confidence intervals.
Why it matters
This review aggregates evidence for an accessible, low-cost sleep intervention, identifying an optimal window (1–2 hours before bed) and water temperature range (40–42.5 °C) to facilitate thermoregulatory heat dissipation and improve sleep onset.
Limits
The abstract provides no quantitative effect sizes, confidence intervals, or total participant count. The authors note that findings are limited by the scarcity of available studies, leaving optimal timing, duration, and exact physiological mechanisms open to further investigation.
Cited by
- supports Core body temperature must drop by approximately 1 to 3 degrees to initiate and maintain deep sleep, and must rise by 1 to 3 degrees to wake feeling refreshed.
- supports In order to fall asleep and stay deeply asleep, human body temperature must decrease by approximately 1 to 3 degrees.
- supports In order to fall asleep and stay deeply asleep, core body temperature must decrease by about 1 to 3 degrees, and must increase by about 1 to 3 degrees to wake up feeling refreshed.