You’ve no doubt had trouble falling asleep at some point in your life (if you’re like me, you unfortunate soul, most nights of your life) and you’ve no doubt ran across the advice to take a warm bath or shower to combat insomnia, right?
It’s fairly common advice, but…what’s the actual science behind it?
Researchers in the Cockrell School of Engineering at The University of Texas (UT) at Austin set out to learn just that, and their findings (which were recently published in the journal Sleep Medicine Reviews) could help you make the most out of this age-old advice.
While much of the science to support the links between “water-based passive body heating” (e.g. taking a bath before bed) and improved sleep has already been established, Shahab Haghayegh, a Ph.D. candidate in the Department of Biomedical Engineering and lead author on the paper, stated:
When we looked through all known studies, we noticed significant disparities in terms of the approaches and findings. The only way to make an accurate determination of whether sleep can in fact be improved was to combine all the past data and look at it through a new lens.
So, the UT researchers teamed up with the UT Health Science Center at Houston and the University of Southern California and reviewed more than 5,000 studies and pulled information to specifically explore the effects of water-based passive body heating on several sleep-related matters: sleep onset latency (SOL), wake after sleep onset, total sleep time, sleep efficiency (SE), slow wave sleep, and subjective sleep quality.
What did the researchers find?
The researchers found the optimal timing of bathing for cooling down of core body temperature in order to improve sleep quality is about 90 minutes before going to bed. Warm baths and showers stimulate the body’s thermoregulatory system, causing a marked increase in the circulation of blood from the internal core of the body to the peripheral sites of the hands and feet, resulting in efficient removal of body heat and decline in body temperature. Therefore, if baths are taken at the right biological time — 1-2 hours before bedtime — they will aid the natural circadian process and increase one’s chances of not only falling asleep quickly but also of experiencing better quality sleep.
A warm bath or shower of between 104 and 109 degrees Fahrenheit is optimum for improving your overall sleep quality, and scheduling that bath or shower 90 minutes (or between one and two hours) before bedtime is best for speeding up the time it takes you to fall asleep by 10 minutes.
Aha! So now you have a bit more direction.
Give it a try tonight. Whether or not you have difficulty sleeping, try having a nice warm bath about an hour and a half before your usual bedtime, and see how it affects your sleep tonight. Come back in the morning and let us know how it goes!