Over the last few months, we’ve read dozens articles claiming that you should sleep naked to sleep better. Our team at Cosmo was skeptical. If sleeping naked is such a miracle cure, why aren’t doctors recommending it? We decided to look at the facts and in the end we were surprised how many websites misquoted research or didn’t look at research at all. Here’s what we found:
Sleeping naked can be beneficial, but only if you are already too warm
Many websites cite “new research” by Dr. Van den Heuvel from the University of South Australia to support claims that sleeping naked improves sleep quality. The premise is that cooler temperatures are good for sleep. The source– a press release from 2004– makes no mention of sleeping naked.
What Van den Heuvel’s research does say is that the inability to regulate body temperature is a common cause of insomnia, especially among 20–30-year-olds. Some cases of insomnia may simply be an inefficiency in dissipating heat:
“To drop the core temperature, the body needs to act like a radiator, with heat from the central core transferring to areas such as the hands, face and feet, causing the peripheral skin temperature to rise and then lose heat to the surrounding environment,” Dr Van den Heuvel said.
According to the researcher, it takes only a half degree of temperature Celsius to throw off sleep. It would seem as though removing excess clothing that traps heat, especially socks, could significantly improve sleep for some people.
We’ll take this as evidence that sleeping naked is beneficial for sleep, but only if you have trouble keeping cool to begin with. This should be obvious to anyone who ever spent a summer night without air conditioning or slept with too many layers in the winter.
In most situations sleeping naked will not improve rest.
The research everyone misunderstood
In addition to the aforementioned press release from Australia, most articles also cite a study from the Netherlands (because Europeans know everything). As before, the idea is that cooler temperatures, and thus removing clothes, improve sleep. It seems no one read this research, because it says exactly the opposite: keeping warm improves sleep.
As part of the study, the test group wore a bodysuit that increased surface degree body temperature 0.4 degrees Celsius relative to the control group.
Participants noticed a marked increase in nocturnal slow-wave sleep and longer sleep duration as a result of the temperature increase. The improvements were most marked among elderly insomniacs, who experienced a doubling of the proportion of nocturnal slow waves.
Many reputable sites, including one written by a doctor, cite this article as proof that lower body temperature improves sleep. It seems nearly every journalist misunderstood the article and claimed the exact opposite of the authors’ results. The researchers increased surface body temperature. They did not decrease it.
Keeping your extremities unclothed may have benefits
Curiously, there many be benefits to keeping the extremities of your body cool (and thus unclothed) and keeping the body’s core warm. A study published in the Journal of Neurology, Neurosurgery, and Psychiatry found that proximal (close to the torso) skin warming improved deep sleep and reduced wakefulness in narcolepsy patients, while distal skin warming (away from the body) reduced deep sleep. Note that this study was conducted by one of the same researchers from the previous article.
Interestingly, warming the skin closest to the body’s core and cooling skin in the extremities had the optimal effect. With this combination participants noticed the greatest improvements in sleep quality: a 160% increase in short-wave sleep, a 50% increase in REM sleep, and a 68% decrease in wakefulness.
So what should you do?
The key issue here is not whether you should sleep with our without clothes, but determining the optimal body temperature for sleep. Published research primarily examines the impact of surface body temperature on different stages of sleep. The most compelling evidence shows that, at least for narcoleptics, cooling only the extremities is beneficial for sleep. Conversely, slightly warming the core surface improves sleep.
Notably, there is no evidence that shows that sleeping naked is bad for you. Many people report sleeping better in cool environments. And almost everyone can attest to waking up in the middle of the night feeling too warm. The author of this article can report throwing his clothes off halfway through the night on many occasions to cool off.
We would like to see more research on how surface body temperature affects each stage of sleep. It may very well be that certain temperatures work better for certain people depending on individual circumstances. What helps one stage of sleep (ie warmth for deep sleep) may impair another (falling asleep). Research should also examine how differences in temperature throughout the day impact sleep. Perhaps a shift in ambient temperature from warm to cold to simulate life in nature is beneficial, for example.
Much like self-help websites have incorrectly used research to promote the virtues of cold showers, we think the Internet is well-intentioned but ill-advised in recommending sleeping naked as the best way to rest. Our advice is to try different approaches and decide what works best for you. If you’re currently sleeping naked, keep sleeping naked. If you prefer sleeping with clothes, this may actually be better for some people. There’s no need to ditch the Star Wars pajamas just yet.