Will you sleep better naked when it's hot? Sleep researchers weigh in

Sleep researchers offer a few things to bear in mind from fabrics to hormones plus that you may want to wash your sheets more often as they will be absorbing more sweat. — Photos: dpa

If the weather is warm where you are, you may be tempted to skip putting on your nightwear altogether.

Does that make sense? We asked the experts - after hearing that some of us are sleeping without our clothes on anyway. A Yougov poll found 15% of adults in Germany prefer to sleep naked - mostly men.

Does sleeping naked help our bodies to relax more?

Not generally, says Hans-Günter Weess of the German Society for Sleep Research and Sleep Medicine (DGSM). "We’re facing another spell of hot nights. There are certainly people who spontaneously choose to sleep naked.”

The key, he says, is feeling comfortable. "Then I’m relaxed, then I’m at ease - ‘cool,’ in other words. That’s the ideal way to get a good night’s sleep.

No matter whether you sleep naked or not, the key is feeling comfortable.

I've heard that people who sleep without clothes have less body odour.

"That’s true,” says Bavarian dermatologist Petra Ziegler from the Professional Association of German Dermatologists (BVDD). "Sweat itself is odourless. It’s only when it’s trapped - for example, by clothing that sweat sticks to - that bacteria have more of a surface to attack. They then break down proteins and sebum on the skin. That’s what actually causes body odour.”

Through sweating, the body loses around three-quarters of a litre of sweat at night. Sometimes, however, this isn’t entirely undesirable.

"Of course, we don’t want to smell bad. But our body odour contains a bit of our DNA. When it comes to forming a bond with a partner, it literally matters whether you can stand the smell of each other or not.”

Do people who sleep naked and in a cool room burn more calories?

"That depends more on how long you sleep,” says Weess, head of the sleep medicine department at the Pfalzklinikum Klingenmünster in Rhineland-Palatinate. "If, like most of us, I’m somewhat sleep-deprived, then I don’t burn as much energy. Sleeping for a long time, on the other hand, is good for calorie burning because we release leptin whilst we sleep." This satiety hormone is produced in fat cells.

In this respect, a long night’s sleep could help you lose weight. "But only if we also watch our calorie intake during the day.” It is certainly plausible that more calories are burnt in a cooler environment, as the body has to expend more energy to keep itself warm. "On the other hand, however, this causes physical stress - and that leads to poorer sleep.”

Is tight, non-breathable nightwear problematic for health reasons?

"Yes," says dermatologist Ziegler. "As far as possible, even if we don’t want to sleep completely naked, we shouldn’t wear tight underwear made of synthetic materials at night. Nightwear must allow the genital area to breathe. Otherwise, the yeast Candida albicans will thrive.” This can lead to vaginal infections.

It has also been proven that tight underwear contributes to reduced sperm production. "Because sperm love it when it's cool.”

You shouldn’t wear tight underwear made of synthetic materials at night.

People who sleep naked feel sexy.

"That’s certainly possible,” says dermatologist Ziegler. "With a surface area of up to two square metres, the skin is our largest sensory organ. Sleeping naked can therefore be associated with positive sensory experiences.”

Even without a sexual context, this is good for the couple’s bond. "Skin-to-skin contact increases the production of the ‘cuddle hormone’ oxytocin. This boosts relationship satisfaction - and the body also releases more endorphins - commonly known as ‘happiness hormones’.”

Is it true that people who go to bed without clothes are more likely to catch a chill?

"It’s not out of the question. It can also lead to muscle tension,” says sleep researcher Weess. "On hot nights, all the windows are often left open to create a draught, or a fan - or air conditioning - is running. You really do need to be careful.”

Does sweat cause problems in the skin folds?

"We always have bacteria on our skin,” says Ziegler. "We live alongside millions of them, mostly in harmony.”

However, some bacteria or fungi can occasionally multiply excessively and cause problems. "This issue with skin folds - for example, in the armpits or the groin area - naturally also occurs during the day when we sweat in summer. Generally speaking, applying a zinc paste helps. It blocks moisture to some extent and also has an anti-inflammatory effect.”

If you do sleep naked, bear in mind you should pay much closer attention to hygiene.

"Sweat can’t just vanish into thin air,” says dermatologist Ziegler. "It soaks into the sheets and bed linen. That’s why, for hygiene reasons, we should change them twice as often - that is, about once a week. Otherwise, the bed will start to smell."

If you are allergic to house dust mites - which live in every mattress and feed on dead skin cells - and if you sleep unclothed then get a tight-fitting mattress cover. "I would only ever recommend nightwear for people with atopic dermatitis,” Ziegler says. That also applies to those with open wounds.

In summer, natural materials such as silk or very fine cotton fabrics are helpful. – dpa