Studies have shown that in general, the optimal room temperature for sleeping is quite cool, around 60 to 68 degrees Fahrenheit, and temperatures much above or below this range can lead to restlessness.
But a new study suggests there are nuances to this phenomenon, and that a restful night’s sleep may be more complicated than simply turning down your thermostat.
Thermoregulation—your body’s heat distribution system—is strongly linked to sleep cycles. Even lying down can induce sleepiness by redistributing your body heat from your core to your periphery.
Sleep deprivation has virtually the same effect on your immune system as physical stress or illness, which explains in part why lack of sleep is associated with an increased risk of multiple chronic diseases. Therefore, high-quality sleep is critical to your health.
In this article, I’ll be discussing the latest research on sleep temperature, as well as other factors that can ease you into a blissful night’s slumber.
Cooler Heads Prevail
While you sleep, your body’s internal temperature actually drops to its lowest level of the day, generally about four hours after you fall asleep.
Research has determined that insomniacs typically have a warmer core body temperature just before bed than normal sleepers, which leads to heightened arousal and difficulty drifting off.
Many scientists believe that anything that mimics your body’s natural temperature drop may help promote sleep—such as the abrupt temperature change that occurs shortly after getting out of a hot bath.
Keeping a “cool head”—or more specifically, a cool brain—appears to induce sleepiness. Researchers from the University of Pittsburgh School of Medicine found that a cap worn by insomniacs filled with cool circulating water helped them sleep almost as easily as people without sleep disorders.
Those whose caps were set to the coolest temperatures were able to get more sleep than those whose caps were set slightly warmer. The caps’ success can be explained by the fact that heightened brain activity raises your brain’s temperature.
Many insomniacs report that they can’t fall asleep because they “can’t turn their brains off” at night, but the cooling cap helped resolve this. Researchers concluded that their extra brain activity was keeping their brains too hot for sleep.
Cooling off your brain makes sense, as melatonin (your sleep hormone) works in part by lowering your body temperature. Yawning may also serve to cool your brain by drawing a bolus of cool air into your sinuses.
Your brain temperature is higher when you’re sleep deprived, which might explain why exhaustion triggers excessive yawning.
The Secrets to Burning More Fat While You Sleep
New research from the National Institutes of Health (NIH) suggests that sleeping in a cool room has significant calorie- and fat-burning health benefits.
According to Dr. Francesco Celi, Chairman of Virginia Commonwealth University’s Division of Endocrinology and Metabolism, even a small reduction in room temperature helps your body “burn calories and dispose of excess blood sugar”—thanks to your body’s brown fat.
Brown fat generates heat by helping you burn calories, which is why it’s being explored as a tool for weight loss, healthy metabolism, and more. The more brown fat you have, the better, as there are direct correlations between your level of activated brown fat and optimal metabolic markers.
People with more brown fat have a faster metabolism, better blood sugar control, and higher insulin sensitivity when exposed to cold temperatures. As you age, the activity of your brown fat decreases, which helps explain why there’s a tendency to gain weight with age. However, exercise may help prevent this.
Unfortunately, other evidence suggests that the optimal temperature for activating brown fat may NOT be the best for a sound sleep.
Shivering Activates Brown Fat—But Hampers Your Sleep
According to Dr. Celi, there is evidence pointing to shivering as the mechanism that triggers brown fat to produce heat and burn calories. Like exercise, shivering triggers your muscles to secrete a hormone that stimulates energy use in your brown fat cells.
But shivering is not conducive to sleeping soundly, as evidenced by research from Dr. Eus van Someren and colleagues at the Netherlands Institute for Neuroscience.
While a dip in core temperature before bedtime flips on your “time for bed” switches, Someren’s research indicates that deep, restful slumber requires you to keep your skin temperature “perfectly comfortable.” So, if you’re thinking about chilling yourself during the night to boost your health and metabolism, it simply won’t work—you’ll end up sleep deprived.
In fact, Someren’s work and that of others suggest that skin temperatures in the range of 90 degrees may be optimal. Typically, all that’s required to get your skin to 90 degrees Fahrenheit are thin pajamas, plus a sheet, and a light blanket—even if your bedroom thermostat is set to 65.
So, if you’re one to turn the heat way down and crawl under a big puffy comforter, you may sleep well, but you’re probably not experiencing much brown fat activity. The other thing that can happen if your bedroom is too chilly is that the blood vessels in your skin will constrict, locking in heat and raising your core temperature to a point at which your sleep can be disturbed.
If you introduce a bed partner into the mix—and it doesn’t matter whether he or she is the two-legged or four-legged variety—then things get even more complicated, especially if you each have different Goldilocks zones for comfort.
Sharing your sleep sanctuary can be tricky business. Finding your “perfect sleep temperature” is a bit of a process and differs for everyone. But body temperature is only one of many factors that control the quality and duration of your sleep.
Sleeping in the Buff May Be Beneficial
Professor Russell Foster of the University of Oxford recommends ditching your pajamas to improve your slumber—which is actually done by one-third of all adults in the US, according to one study. If you’re wearing lots of bedclothes, it may be more difficult for your body to regulate its temperature.
With or without pajamas, it’s important to make sure your hands and feet are warm because if they aren’t, the blood vessels near your skin constrict and reduce blood flow in an effort to prevent heat from escaping, and this prevents your core temperature from dropping easily. Conversely, warming your skin causes your peripheral blood vessels to widen, promoting heat loss. To summarize, if you want to fall asleep easily, you’ll need to be warm enough that your blood vessels won’t constrict, but not so hot that your body can’t cool down.