In light of a recent Daily Mail article, "Why Sleeping Naked Could Cut Your Risk of Diabetes ... Not to Mention Ward Off Infections, Trim Your Waistline and Make You Less Exhausted" [Nov. 24, 2014], I was wondering whether you think the government should ban pyjamas? —Sarah Chekroud
A pajama ban might be slightly overstepping things—firstly, because I, for one, don't want to be the person going around policing it. Secondly, at the risk of sounding puritanical, getting naked might be overrated. The claim, while it does follow a pattern distantly related to logic, is nowhere near scientifically proven. And while there's no denying that regular nudity will very likely improve certain aspects of your life, unfortunately there are no reported links thus far between orgasms and insulin sensitivity. We'll be the first to let you know when anything turns up.
Let's acknowledge that the Daily Mail—a British tabloid not best known for its science reportage—has it essentially right on at least one point: sleep is good. When you don't get enough of it, scary things tend to happen. Microsleeps, for instance—without sufficient sleep the brain forces us to take tiny involuntary naps, more or less pulling the plug on our consciousness every so often. Add in the fact that the cognitive effects of a week of reduced sleep have been found equivalent to a blood alcohol level of 0.089, and you see why sleep deprivation is a serious menace to car, air and space shuttle traffic alike. The immune system and reaction times fall victim to drowsiness too, as do fine-motor function, working memory, and (need we even mention it?) mood.
Lack of sleep can also make you fat. For one thing, sleepy people tend to eat more. Brains need stimulants to keep from crashing, and sugar is an easy (if poor) substitute. Also, fewer hours asleep equals more hours awake to eat donuts. The more people are exposed to food, the more likely they are to eat it. And leptin and ghrelin, hormones that play a major role in appetite regulation, are dependent on sleep quantity and quality—as is glucose regulation. This means that not only can reduced sleep cause increased hunger and appetite throughout the day, it makes binge-eating ice cream even worse for you than usual. Maybe unsurprisingly, a long-term study of 68,000 women found that compared to those who slept seven hours a night, women who slept five hours or less were 15 percent more likely to become obese.
And being overweight can, of course, increase your risk of diabetes. There's evidence, too, that the body's sensitivity to insulin is much worse after less sleep, or interrupted sleep. So the idea of a connection between sleep and diabetes risk certainly isn't crazy.
All this established, we'll move on to the central question: to strip or not to strip? This is where things get a little iffy. To support the big claim made in their headline, the Daily Mail cites a study published last summer in the journal Diabetes reporting that five men who slept in colder temperatures for a month showed significantly better insulin sensitivity and developed more brown fat. Brown fat is metabolically active (as opposed to the Crisco that coats the rest of our bodies), and is considered good because it takes sugar out of your bloodstream to maintain body temperature. So, OK: sleeping in the cold is better for you. But the Mail's crack reporting team leaves out a key detail: these men weren't naked—they were all thoroughly pajama-ed.
So far, Cecil 1, Daily Mail 0 (not that we keep track of these things). But we're not done here: the Mail also claims more basically that "going naked means a good night's sleep." Admittedly, getting quality sleep is a surprisingly tricky process. Your core body temperature needs to drop almost a degree Fahrenheit for you to fall and stay asleep, meaning the ideal bedroom should be fairly cool, and bundling up too much is counterproductive. But in the process your skin temperature needs to increase, thus allowing blood vessels to expand enough to release that excess core heat. The Mail insists that being naked helps make this complex thermoregulation happen, but to defend the point it winds up relying on a 2008 Dutch study that found subjects slept more deeply and soundly with their skin warmed by water-filled thermosuits. Again—and I hate to have to mention it—these subjects obviously weren't naked.
It's not hard to see how a paper that specializes in celebrities' beach bodies and baby bumps might oversell the nudity concept for clickbait purposes. Some optimized combination of room temperature and skin coverage could well improve your sleep and/or even help build brown fat, either of which may in turn ultimately lower your diabetes risk, and nakedness could conceivably play a role in such a scenario. But since a. no one has yet gone full monty in a clinical setting and b. over-thinking all this provokes more insomnia-inducing anxiety than not, I hereby pardon all pajama-wearers. Thermosuits, birthday suits—wear whatever helps you sleep at night.
Send questions to Cecil via StraightDope.com or write him c/o Chicago Reader, 350 N. Orleans, Chicago 60654.