Taking a warm bath an hour or two before bedtime could be the key to getting a better night's sleep.
A group of biomedical engineers from the University of Texas and the University of Southern California analyzed that link water-based passive body heating (bathing or showering with warm or hot water) with improved sleep quality.
Bathing In Warm Water And Sleep
"When we looked through all known studies, we noticed significant disparities in terms of the approaches and findings," explained Shahab Haghayegh, lead author of a study published in the journal Sleep Medicine Reviews. "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 reviewed a total of 5,322 studies and extracted pertinent information to explore the effects of water-based passive heating to factors related to sleeping such as sleep onset latency (amount of time it takes to transition from wakefulness to sleep), sleep efficiency (amount of time spent in bed intended for sleep), and subjective sleep quality.
How To Improve Sleep Quality According To Science
They found that showering or bathing in water between 104 and 109 degrees Fahrenheit (40 and 42 degrees Celsius) improved overall sleep quality. If scheduled an hour or two before bedtime, showering or bathing in warm water can make a person fall asleep faster by an average of 10 minutes.
The researchers explained that warm baths stimulate the thermoregulatory system of the body, causing an 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 lower body temperature.
The body temperature is involved in the regulation of the circadian rhythm. Previous studies have found that the body temperature is about 2 to 3 degrees Fahrenheit higher in the late afternoon to early evening compared to during sleep.
The core body temperature drops about 0.5 to 1 degree Fahrenheit an hour before the usual sleep time. It drops to its lowest level between the middle to the later span of sleep. It rises again in the morning, serving as an internal alarm clock to wake the body up.
A warm bath, if taken during the right time, can aid in falling asleep faster and improve the overall sleep quality.