The answer to a good night’s sleep might be found in your bathtub

22 Jul 2019

Image: © Fabio Principe/

Biomedical engineers have pored through data to find that a particular amount of time in the bath helps you get a good night’s sleep.

The question of how to get a good night’s sleep remains ever-present for those with sleep issues, but researchers at the University of Texas at Austin believe they’ve found an answer.

In a paper published to Sleep Medicine Reviews, the biomedical engineers pored through thousands of studies linking water-based passive body heating, or bathing and showering with warm or hot water, with improved sleep quality.

It showed that taking a bath between one and two hours before bedtime would significantly improve your sleep. Additionally, the ideal temperature would be between 40 degrees Celsius and 43 degrees Celsius.

“When we looked through all known studies, we noticed significant disparities in terms of the approaches and findings,” said Shahab Haghayegh, 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.”

A total of 5,322 studies were analysed as part of this latest work, which explored water-based passive body heating and the length of time it takes to accomplish the transition from full wakefulness to sleep, the total sleep time, and how ‘efficient’ a person’s sleep was. By taking a bath at this newly discovered optimum time, the researchers said it could hasten the speed of falling asleep by an average of 10 minutes.

Warm baths and showers stimulate the body’s thermoregulatory system, causing a noticeable increase in the circulation of blood from the internal core of the body to the peripheral sites of the hands and feet. This results in efficient removal of body heat and decline in body temperature, which is necessary for a good night’s sleep.

The average person’s circadian cycle will see body temperature drop fractionally an hour before their regular bedtime, dropping to its lowest in the middle of the night and rising again before waking.

Colm Gorey was a senior journalist with Silicon Republic