What to do when it’s too hot to sleep

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There are many things that can hamper a good night’s sleep: late-night Netflix binges, inadequate exercise, a late-afternoon latte. But a hot bedroom can be one of the most frustrating.

For most people, optimal sleeping conditions are between about 60° and 68° F (15 to 20 C) and 40 to 60 per cent humidity. Anything outside of these ranges, experts say, and sleep quality plummets. Multiple nights spent tossing and turning can leave you cranky and unproductive during the day, and over time, poor sleep has been tied to serious health consequences.

In the coming years, experts predict that—because of climate change—more heat waves will ripple across the globe with increasing intensity.

But with a few smart tips, you can transform an uncomfortably hot bedroom into something more tolerable, ensuring sounder slumber on even the warmest nights.

The perils of poor sleep

Few studies have looked into how sleeping in a hot room might affect your health, says Lauren E. Hale, PhD, a professor of family population and preventive medicine at Stony Brook University in New York and editor-in-chief of the journal Sleep Health.

But in general, scientists know that getting enough restorative sleep—in both time and quality—“is critical for the optimal functioning of every organ in the body,” she says.

Studies have linked long-term insomnia to an increased risk of high blood pressure, diabetes, cardiovascular disease, anxiety, depression, work and family problems, diminished quality of life, and even early death.

Why heat can make you feel beat

Your body temperature naturally fluctuates throughout the day, helping to regulate your internal clock, or circadian rhythm. When it rises, you tend to feel alert and awake, and when it falls, you tend to feel sleepy.

The ideal sleeping temperature differs from person to person, but in general, your body’s core temperature needs to drop for you to drift off at night. That slows down your metabolism and coincides with the release of melatonin, a hormone that makes you feel drowsy, sending a signal to your brain that it’s time to fall asleep. If your body is overheating at night, Hale says, it’s going to interrupt this process.

And a warm or muggy bedroom doesn’t just make it more difficult for you to cool down and fall asleep. It can make it harder to stay asleep, too. Some studies suggest that the discomfort of sleeping in a hot room can cause more frequent awakenings throughout the night and can disrupt restorative rapid eye movement (REM) sleep.

But the good news, experts say, is that there are things you can do to get relief—even if you don’t have air conditioning.

How to chill when it’s hot out

Block out the sun. If it’s hotter outside than inside, pull down the shades or close the blinds, and shut your windows, says Alcibiades Rodriguez, MD, an associate professor of neurology and medical director of the Comprehensive Epilepsy Center-Sleep Center at the New York University NYU Langone Health medical centre. That helps keep cool air in and hot air out. Closing the blinds has other benefits, too, because a dark room promotes a sounder sleep.

Cool down your room. Dial down the temperature and humidity in your bedroom with a window AC unit or central AC.

“If you aren’t fortunate to have those in your house or bedroom, then you can think about creating cross-ventilation,” Hale says. Open the windows (in the best-case scenario, more than one) and use a fan to circulate the air. If you have only one window in your bedroom, position a fan there so that it circulates the cooler nighttime air inside.

A bonus of having a fan, says Douglas Kirsch, MD, a clinical professor in the department of neurology at the Wake Forest School of Medicine, is that it provides white noise, “which often helps block other noises and improves sleep quality.”

An important note about fans, however: Public health agencies warn that using an electric fan in extremely hot conditions can be ineffective. The U.S. Centers for Disease Control and Prevention says that when indoor temperatures are above 90° F (32 C), a fan can actually increase body temperature.

And a study in Annals of Internal Medicine found that a fan’s effectiveness may be related to humidity—or the lack of it. When the researchers evaluated how well a fan cooled 12 healthy men, they found that it was helpful in reducing heat stress in the study subjects when conditions were hot and humid. But in very hot, dry heat, using a fan actually raised the men’s internal temperature and heart rate.

Chill your bed. Try sealing your bedsheets and pillowcases in a plastic bag and sticking them in the freezer, Hale says. And to steer clear of overheating in your bed, avoid silk or polyester blended sheets; 100 per cent cotton is best, according to the U.S. National Sleep Foundation, because it breathes better.

Some bed-cooling technologies, such as chilled mattress pads and toppers or cooling blankets, might also help. When CR tested them, we found that those that worked by chilling water before sending it through tubes in the pad worked better than those that used air.

Choose a mattress that sleeps cool. If your bed-chilling attempts aren’t working, your mattress might be the problem. Some types, such as those made from foam, sleep warmer than others, such as innerspring mattresses.

Lower your body temperature. Taking a cold shower before bed can help lower your core body temperature and help promote sleep, Rodriguez says. You can also pat your bare skin with a damp towel or washcloth (while in your bed or just before you go to sleep), or try a cool compress on your forehead.

Stay hydrated. Warm temperatures make you thirsty, and getting out of bed for water disrupts sleep. Making sure you’re hydrated before you hit the hay and keeping a bottle or glass of water near your bed can minimize the need to leave your bedroom for middle of the night water breaks, Rodriguez says.

Sleep solo. If you share a bed with your partner, that extra body heat can zap the quality of your sleep. Consider sleeping separately on really hot nights, Hale says. “That might have other benefits as well, if your partner snores or kicks,” she says.

Written by Julia Calderone, updated by Catherine Roberts, Consumer Reports