Sleep Better,

Ignore Everything the Internet Says about Sleeping Naked

Person sleeping naked

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.


Daniel is the founder and CEO at Cosmo. When he's not helping the world sleep better, he enjoys swimming, photography, and brewing coffee.

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