Researchers at the University of Southern California have found that having a bath 90 minutes before bedtime could be the key to a good night's sleep.
A study that analysed more that 5,000 studies on sleep-related conditions, found that having a bath between 40°C and 42°C could increase the speed of falling asleep by ten minutes.
Why is this the case? It's all to do with body temperature.
Reads Science Daily: "Body temperature, which is involved in the regulation of the sleep/wake cycle, exhibits a circadian cycle, being 2-3 degrees Fahrenheit higher in the late afternoon/early evening than during sleep, when it is the lowest.
The average person's circadian cycle is characterized by a reduction in core body temperature of about 0.5 to 1 F around an hour before usual sleep time, dropping to its lowest level between the middle and later span of nighttime sleep. It then begins to rise, acting as a kind of a biological alarm clock wake-up signal. The temperature cycle leads the sleep cycle and is an essential factor in achieving rapid sleep onset and high efficiency sleep.
The researchers found the optimal timing of bathing for cooling down of core body temperature in order to improve sleep quality is about 90 minutes before going to bed. 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."