Scientists have proven that taking a bath 90 minutes before going to bed can help you get a better night's sleep.

Researchers at the University of Texas in Austin analysed thousands of studies on "water-based passive body heating" or bathing and showering with hot water.

The biomedical engineers found that bathing between one and two hours before bedtime in water between 40C (105F) and 42C (109F) can significantly improve sleep.

"When we looked through all known studies, we noticed significant disparities in terms of the approaches and findings," said Shahab Haghayegh, a PhD candidate 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 team published its paper in the journal Sleep Medicine Reviews after analysing 5,322 studies.

A lot of the science proving how a bath or shower improves sleep is already established.

Both sleep and core temperature in humans are regulated by something called the circadian clock, which is located within the brain's hypothalamus which sets the pattern for our bodily functions.

Our body temperature is closely involved in regulating our sleep, and our temperatures can be up to three degrees Fahrenheit higher in the late afternoon and early evening than when we sleep.

Image: Baths around 40C (105F) are ideal

As our temperature rises during the night it works like a kind of biological alarm clock which ultimately disrupts our sleeping.

According to the researchers: "The temperature cycle leads the sleep cycle and is an essential factor in achieving rapid sleep onset and high efficiency sleep."

They discovered that perfect timing between having a bath and our core body temperature cooling down to improve sleep quality is 90 minutes.

"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," according to the researchers.

"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."