The effects of sleeping in a cold room

Sleeping in a cold room might not sound like a game-changer, but science says otherwise. According to Dr. Kelvas, when your bedroom is either too hot or too cold, your body struggles to regulate hormones that control sleep, making it harder to fall or stay asleep. The Sleep Foundation recommends keeping your bedroom between 60°F and 68°F (15.5°C to 20°C), a range shown to support your body’s natural cooling process and improve sleep quality and onset time.

The human body is equipped with a thermoregulatory system designed to maintain a stable internal temperature despite external changes. This system kicks into action through processes like sweating, shivering, and altering blood flow near the skin. Sweat cools you down when you overheat, while shivering generates heat when you’re too cold. Blood vessels also play a role—dilating to release heat or constricting to retain it, depending on your body’s needs.

You’ve probably noticed how this works when you’re getting ready for bed. Cold feet can keep you up, while slipping on socks can suddenly make you feel cozy. Or maybe you’ve tossed one foot out from under the blanket to cool off. These small actions reflect how sensitive our sleep is to temperature.

Temperature doesn’t just affect comfort—it’s deeply connected to our internal clock. It acts as a “zeitgeber,” or a time cue, guiding our circadian rhythm. In fact, studies of pre-industrial societies show people typically fell asleep as temperatures dropped and woke up before dawn, when it was coldest. During sleep, especially in the early stages, your core body temperature begins to decline and reaches its lowest point during deep sleep. This drop isn’t random—it’s critical for a good night’s rest.

Melatonin, often known as the sleep hormone, increases in a cool environment. While it’s heavily influenced by light exposure, temperature plays a significant supporting role. On the flip side, if your room is too hot, your body struggles to cool down, and this can negatively affect both REM sleep—where dreaming and emotional processing occur—and slow-wave sleep, where the body repairs itself and clears toxins from the brain.

In one study involving elderly men, even slight heat exposure during the night led to disrupted REM sleep and increased sweating. Another study out of UCLA showed warm-blooded animals with higher body temperatures got less REM sleep than their cooler counterparts. Humidity makes things worse. High humidity has been linked to more wakefulness and fewer restorative sleep phases, thanks to its interference with your body’s ability to cool down.

Sleeping in a room that’s too cold isn’t great either. If your body has to work too hard to stay warm, it can prevent you from slipping into the deeper stages of sleep. But if you find that sweet spot of a comfortably cool room, the benefits are worth every shiver.

For starters, a cooler room can lead to better quality sleep. When your environment supports your body’s natural nighttime cool-down, it helps regulate melatonin and reduces the stress hormone cortisol, letting you sink into deeper sleep with fewer wakeups from night sweats or overheating.

You’ll also fall asleep faster. Since your core body temperature needs to drop before you drift off, a cooler environment helps that process. Studies show that people with insomnia often have higher core body temperatures, which disrupts sleep. A chillier room helps sidestep that problem, allowing your circadian rhythm to work as it should.

And then there’s weight management. Cold temperatures activate brown fat—a type of fat that burns calories to generate heat. A study from Australia found that men who slept in 66°F (18.8°C) rooms for a month nearly doubled their brown fat, which in turn helped them burn more belly fat and boost metabolism.

Better still, cooler sleeping conditions may reduce your risk for diseases. The same Australian study showed participants burned more calories throughout the day when they slept in cooler temperatures. Cold sleeping environments also help regulate insulin, improving sensitivity and potentially lowering the risk of type 2 diabetes and other metabolic issues.

There’s even evidence suggesting that cooler sleep environments may protect brain health. Research in JAMA Neurology shows that poor sleep—both too little and too much—is linked to higher risks of Alzheimer’s, greater depressive symptoms, and cognitive decline. Since deep, restorative sleep is when your brain flushes out harmful toxins, anything that helps you stay in those sleep stages longer is a good thing.

If you’ve ever found yourself sleeping with a cold towel during a heat wave, you already know how temperature impacts rest. Women going through menopause often experience heightened sensitivity to temperature changes. Even natural fluctuations throughout the menstrual cycle can make a difference.

The message is clear: turn down the thermostat. Whether you’re chasing better sleep, sharper focus, improved health, or even a slimmer waistline, the temperature of your bedroom plays a bigger role than you might think. So tonight, open a window, shed a layer, and embrace the cool—you might just wake up feeling better than ever.