Why is it hard to sleep in the heat? Experts explain.

The temperature of your bedroom may be affecting your sleep. (Getty Images)

Nobody enjoys waking up in the middle of the night, especially if you don’t understand why you’re even awake in the first place. But for more than 35% of adults who get less than 7 hours of sleep each night, this may be a common scenario. There are several reasons people get less sleep — stress, caffeine late at night or taking too long of a nap during the day — but one overlooked reason you may not have considered is temperature.

As the planet’s warming trends continue because of climate change, we’re on course for warmer winters and hotter summers. Your bedroom is no exception. “If you look at the projection of temperatures across the next 50 years, what you find is that global temperatures are going to be increasing, and it’s going to influence people’s sleep,” explains Sara Mednick, a cognitive neuroscientist at the University of California, irvine

Of course, you’re not doomed to spend your nights sleeping like you’re in a sauna. Yahoo Life spoke with experts on what heat does to your sleep, the ideal bedroom temperature, and steps you can take today to make your bedroom more conductive to a good night’s rest.

How does sleeping in a hot room affect your sleep?

When your bedroom temperature is high, there’s a greater chance of having problems sleeping. Even if you can sleep, a too-hot room may prevent you from getting the full restorative benefits of sleep.

Hot temperatures can disrupt stage three sleeps, during which the body enters slow-wave sleep — a deep state of rest in which brain activity slows down to recover from the day. “Heat can affect your ability to get to stage three and the amount of time that you spend in phase three,” Azizi Seixas, an associate professor of psychiatry and behavioral sciences at the University of Miami Miller School of Medicine, tells Yahoo Life.

A 2020 study found that increases in bedroom temperatures were associated with less time spent in REM sleep and in sleeping altogether.

Sleep is also essential for cleaning out waste that builds in the brain from the day before. Seixas says that trouble sleeping could affect the process of clearing the brain of toxins and consolidating memories. “There has been some evidence showing a clearance of the brain in slow-wave sleep to get rid of protein debris, such as amyloid plaques linked to Alzheimer’s dementia and mild cognitive impairment,” he says.

How does sleeping in a freezing room affect your sleep?

While it’s better to be cooler than too hot, sleeping in freezing rooms is not ideal either. That’s because it forces your body to draw blood away from the extremities to warm up and protect your internal organs during sleep. That leads to cold hands and feet, which Seixas says can cause problems when it comes to initiating sleep.

“Temperature plays a significant role in insomnia and getting enough sleep,” says Seixas. “A chillier body can cause sleep fragmentation, as you’re more likely to awaken from any noise or light exposure or cause you to wake up and use the bathroom.”

What’s the best temperature for sleep?

Both experts agree the ideal temperature is 65 degrees Fahrenheit, or between 67 to 69 degrees Fahrenheit. However, a 2018 review looking at optimal sleeping conditions suggested a range of 62.6 to 82.4 degrees Fahrenheit.

Seixas explains that the range in temperature reflects the fact that every person is different. For example, older adults are more sensitive to heat than younger adults.

Why cooler temps are better

Mednick says that keeping the temperature on the cooler side is a cue to your body that it’s time to get to sleep. She explains that the body is heated during the morning and afternoon and gradually uses energy from all the day’s activities. But when you sleep, you enter a mini-hibernation state that significantly decreases your energy, giving your body time to replenish the energy reserves.

“Getting into a cool temperature means that you’re conserving your energy, and it’s a good signal for the brain that you’re going to rest,” Mednick says.

How to get your bedroom and body temperature just right for sleep

Along with sleeping in a dark and quiet room, there are several steps you can take to prepare your body for sleep. While adjusting your thermostat to the ideal sleeping temperature is a simple solution, older adults and people of low socioeconomic backgrounds may lack a thermostat or the mobility to adjust the temperature.

A 2019 review suggests that gradually moving from a hot to cold environment helps prepare the body for sleep by lowering the core temperature and promoting brain activity for rest. One way is to take a hot shower but then use cold water toward the end or leave a hot shower and enter a cool room.

Another option is to keep your feet and hands outside of the bedcovers. “The difference between the core temperature at your belly and the temperature that leaves your body through your feet, hands and head increase your chances of getting into a deep sleep,” Mednick explains. Having your feet and hands unexposed will also give them more exposure to the cooler air outside the blanket.

But if your feet feel too cold at night, Seixas recommends wearing socks to give you extra warmth. Having a heated mattress pad may also help with homes that have poor heating systems in winter months. A 2020 study found that older adults without heat who used bed warmers lowered the time it took them to fall asleep and extended the time they spent sleeping.

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