Researchers have found that having a bath 90 minutes before bedtime can significantly improve the quality of a person’s sleep.
Researchers from the University of Texas at Austin’s Department of Biomedical Engineering have assessed 5,322 existing studies and investigated the impact “water-based passive body heating” – a warm bath – had on total sleep time, subjective sleep quality, sleep onset latency – how long it takes to go from being awake to completely asleep – and sleep efficiency, or the amount of time a person is asleep compared to “the total amount of time spent in bad intended for sleep”.
They found that a bath taken one or two hours before bed, ideally 90 minutes, improve sleep guality. They also discovered the bath sped up falling asleep by 10 minutes on average, while the perfect bathroom temperature was between 104 and 109 degrees Fahrenheit or 40 to 43 degrees Celsius.
“When we looked through all known studies, we noticed significant disparities in terms of the approaches and findings”, said the lead author Shahab Haghayegh. “The only was 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”.
Both sleep and out body’s core temperature are regulated by the circadian clock, the natural, internal sleep-wake cycle which repeats roughly every 24 hours. An average person’s circadian cycle is characterized by a reduction in core body temperature around an hour before bedtime.
Warm baths and showers stimulate the body’s thermoregulatory system, causing an increase in the circulation of blood from the internal core of the body to extremities like the hands and feet, resulting in a decline in body temperature.
Therefore, if baths are taken between one to two hours before bedtime, it will aid the natural circadian process and increase the likelihood of a person falling asleep quickly and getting a night of better-quality sleep.
The study was published in the Sleep Medicine Reviews Journal.