As autumn settles in and temperatures plummet, we’re naturally inclined to twist the dial of the thermostat to a higher, more comfortable setting. But you might want to think twice before you raise the heat in the bedroom. In addition to fostering a sounder sleep, colder rooms may aid metabolic health and assist in other reparative functions.
First, a bit of background. Thermoregulation (the way in which our body distributes heat) and sleep are inextricably linked. While we rest, our bodies’ internal temperature drops to its lowest levels of the day — this general occurs near the four-hour mark. A cooler bedroom, scientists generally agree, complements this natural plummet and assists rest. (Fun fact: chronic insomniacs often have a higher body temperature; one study showed that when cold compresses were placed on sufferers’ foreheads, cooling the pre-frontal cortex, they fell asleep about as quickly as those without sleep issues.)
The generally agreed-upon best setting for sleep? Between 64 and 72 degrees.
It may not be a matter of comfort, but also general health. According to a 2014 study published in Diabetes, dialing down the temp can help lower your risk of certain metabolic diseases. For four months, researchers compared the insulin levels and caloric expenditures of a group of five healthy men sleeping in climate-controlled rooms. They slept for the first month at 75 degrees (widely considered a neutral temperature), then switched to 66 degrees. For the final month, researchers cranked the dial to 81 degrees.
Sleeping in 66 degrees, it turns out, doubled he subjects’ brown fat, the good stuff that helps promote metabolic activity. They also burned more calories through the day and their risk of diabetes was greatly lessened. When they returned to the 80 degree room, these positive effects were reversed. According to the New York Times, the men actually “had less brown fat than after the first scan.”
In addition to the metabolic advantages, colder temperatures are thought to have a positive effect on aesthetics. Melatonin, the sleep hormone, also plays an important anti-aging role, helping facilitate hair growth and repair damaged skin. To reap the pore-shrinking, wrinkle-removing benefits, the temperature should be less than 72 degrees.
However, don’t go overboard. According to a 2013 study from Japan’s Nara Medical University, sleeping in a 57 degree room led to an average eight percent rise in blood pressure come morningtime. Subjects who slept in 76 degree rooms, meanwhile, saw no such issues. The spike was the result of our heart having to work harder to warm up the body.
Climate, of course, is related to more than merely the thermostat. In the Diabetes study, the subjects slept beneath a single sheet. Had they been swaddled in blankets, the results would’ve been different. The same goes for sleeping with a companion — another’s body heat can influence our own.
The one thing that seems to be certain, however, is that cranking up the thermostat doesn’t contribute to a healthy sleep. This winter, go easy on the radiator and keep the temperature somewhere between 64 and 72.