Nearly 40% of UK adults sleep in pyjamas, while just under a third sleep naked, according to a survey of 1,200 people. The average time between pyjama washes is two weeks, with many citing lack of smell as a reason for not washing more often. However, experts say sleeping naked may not be healthier, despite common beliefs.
Contrary to popular opinion, skin does not 'breathe', so sleeping naked offers no respiratory benefit. However, it does help keep the body cooler, which is important for sleep. The optimal sleeping temperature is around 20°C. Overheating can disrupt the body's natural temperature drop after three to four hours, hindering the 'sleep mechanism', according to the Sleep Council.
For those who prefer pyjamas, heavy duvets and fluffy nightwear can cause overheating. Feet should not get too cold either; a hot water bottle is recommended over bed socks, which can become uncomfortably warm.
Regarding reproductive health, wearing underwear at night can increase genital sweating, raising the risk of infections like yeast for women with conditions such as vulvitis. For men, a US study of 500 men found that those who wore boxers during the day and nothing at night had 25% lower sperm DNA fragmentation than those in tight pants day and night. However, another study in the Journal of Urology found no significant link between underwear type and semen quality, concluding it is unlikely to affect male fertility significantly.
Ultimately, experts say the choice of sleeping attire is not a health issue, except for avoiding overheating and ensuring pyjamas are clean. Tracksuits, worn by some survey respondents, are deemed unsuitable for sleep.
