Taking a very hot bath or shower (104 to 109 degrees Fahrenheit) around 90 minutes before bedtime can help you fall asleep more quickly and even improve your sleep quality, according to a new analysis of thousands of studies. As a comparison, the average hot tub is set around 100 to 102 degrees F.
Research has shown that around 35 percent of Americans don’t get the recommended minimum amount of sleep (7 hours) per night. Around 20 percent of Americans are affected by a sleep disorder.
For the analysis, biomedical engineers at The University of Texas at Austin analyzed 5,322 studies linking water-based passive body heating, or bathing and showering with warm/hot water, with improved sleep quality.
“When we looked through all known studies, we noticed significant disparities in terms of the approaches and findings,” said Shahab Haghayegh, a Ph.D. candidate in the Department of Biomedical Engineering and lead author on the paper.
“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.”
The research team explored the effects of water-based passive body heating on a number of sleep-related conditions: sleep onset latency the length of time it takes to accomplish the transition from full wakefulness to sleep; total sleep time; sleep efficiency — the amount of time spent asleep relative to the total amount of time spent in bed intended for sleep; and subjective sleep quality.
The team discovered that the optimum temperature of between 104 and 109 degrees Fahrenheit improved overall sleep quality. When scheduled 1 to 2 hours before bedtime, it can also hasten the speed of falling asleep by an average of 10 minutes.
According to the study, the optimal timing of bathing is about 90 minutes before going to bed. This allows the core body temperature to cool down enough to sleep.
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.
The findings are published in the journal Sleep Medicine Reviews.
Source: University of Texas at Austin