A billboard displays a temperature of 118 degrees Fahrenheit (48 degrees Celcius) during a record heat wave in Phoenix, Arizona on July 18, 2023. Swaths of the United States home to more than 80 million people were under heat warnings or advisories, as relentless, record-breaking temperatures continued to bake western and southern states. In Arizona, state capital Phoenix recorded its 17th straight day above 109 degrees Fahrenheit (43 degrees Celsius), as temperatures hit 113F (45C) Sunday afternoon. (Photo by Patrick T. Fallon / AFP) (Photo by PATRICK T. FALLON/AFP via Getty Images)
VIDEO: Arizona doctor says people are getting burned falling to the ground
01:14 - Source: CNN

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CNN  — 

Are you waking up in a puddle of sweat — if you can sleep at all? That’s the grim reality for millions of people around the globe suffering through severe, unbearable heat waves.

Electric fan in-front of an unmade bed with light coming through a window

July is the hottest month on record for the planet and very likely the hottest period in 120,000 years, according to global climate authorities. “These are the hottest temperatures in human history,” Samantha Burgess, deputy director of the European Union’s Copernicus Climate Change Service, told CNN recently.

It’s expected to get worse: A new study found the number of days of “dangerous heat” — defined as 103 degrees Fahrenheit (39.4 degrees Celsius) — will more than double by 2050 in the midlatitude regions, which include Western Europe and countries such as China, Japan and the United States. Tropical areas could face those temperatures for the majority of the year.

No relief at night

It’s not just the unbearable sunshine — temperatures at night aren’t dropping as they should. Nights are warming faster than days on average in most of the US, the 2018 National Climate Assessment found. That’s dangerous for sleep — a vital period when the body and brain do housekeeping chores such as repairing and discarding old cells and generating new ones.

Warm nighttime temperatures have robbed people around the world of an average of 44 hours of sleep annually during just the first two decades of the 21st century, according to a 2022 study. And unfortunately, daytime naps and longer sleep on cooler nights did not seem to make up for that lost sleep, researchers found.

To get the best quality sleep, experts have long recommended sleeping in a cool room — between 60 and 67 degrees Fahrenheit (15.6 to 19.4 degrees Celsius) is best. What happens when you can’t achieve that during a heat wave?

Studies have shown higher nighttime temperatures increase wakefulness and reduce deep wave and REM (rapid eye movement), both critical to how well the body repairs and refreshes itself at night.

Exposure to heat waves during pregnancy may be associated with adverse outcomes such as preterm birth, according to a 2019 study. Older adults may have higher heart rates and more physiological stress when sleeping in warmer temperatures. A 2008 Australian study even found deaths due to mental and behavioral disorders rose during heat waves, especially for older adults.

10 tips for sleeping in the heat

Learning how to better cope with sleep problems during heat waves might limit the negative impact on our health, according to a team of experts from the European Insomnia Network. Here are their top tips, along with some guidance from experts in the US.

Stay hydrated. Drinking plenty of water during the day can help your body better regulate your temperature at night.

But don’t drink for the hour or two before bed, or you’ll end up waking yourself in the night to go to the bathroom, said sleep specialist Dr. Raj Dasgupta, an associate professor of clinical medicine at the Keck School of Medicine at the University of Southern California. Instead, “try sucking on ice cubes before bed.”

Eat light. Eating lighter, especially for the last meal of the day, can help set you up for better sleep, experts say. Avoid sugar and carb-laden foods, saturated fats and too much fiber as the day goes on, as that can disrupt sleep as well, according to a 2016 study.

Dress lightly. Sleep in the buff or choose loose, cotton clothing — avoid synthetics, which can trap heat next to the skin.

Look for chances to cool the bedroom. If you’re lucky enough to have a cooler period during the day, open windows and doors and start up fans to ventilate the bedroom, then close it off when the temperature rises.

If there are no breaks from the heat, close blinds, pull window shades, and do what you can “to keep the house and bedroom as cool and dark as possible both during day and night,” the network experts suggested.

Avoid alcohol. Drinking booze in the evening dehydrates the body and sets you up for nighttime sweats, said Dr. Phyllis Zee, chief of sleep medicine and professor of neurology at Northwestern University Feinberg School of Medicine in Chicago.

Set aside time to relax. For you and your child, set aside an hour or more before bedtime for calming activities, such as “reading a book, listening to a story or to music. This could help in cooling down and relaxing,” according to the network.

Shower in tepid water. Before you hit that hot sack, take a lukewarm or cool (but not cold) shower or foot bath, which may help to reduce your heat stress and set you up for sleep. How does that happen?

“Your body temperature lowers after you leave the shower or bath as your body adapts to the cooler environment,” Dasgupta said. “This drop in temperature prepares your body for sleep because our body temperature has a natural circadian rhythm — the body is primed to cool down when you lay down and warm up when you get up.”

Find the coolest place to sleep. Try your best to keep your bedroom cooler than 77 degrees Fahrenheit (25 degrees Celsius) if you can. To do so, try using ceiling fans or floor or bedside electric fans, which use “up to 50-times less electricity” than air conditioning,” the review noted.

“There are also fairly inexpensive ice cooling fans that can be placed near the bed,” Zee told CNN. “If you’re unable to keep the bedroom cool, sleeping temporarily on lower floors like the basement (if there is one) will be cooler.”

Keep a regular sleep schedule. If you sleep badly one night, don’t go to bed early the next, experts said. It’s important to stick to a regular bedtime to train the brain that it’s time to sleep, regardless of the temperature.

If you do wake up early and can’t go back to sleep without 15 to 20 minutes, get up and do something soothing and mindless, such as folding laundry, until you’re sleepy. If that doesn’t work, start your day, the network experts suggest.

Exercise safely. Don’t put aside exercise, even in the heat. Try to do some physical activity in the early morning, when it is still relatively cool outdoors, experts suggest, as a key way to keep a regular sleep and wake schedule.

CNN’s Angela Dewan, Laura Paddison and Rachel Ramirez contributed to this report.