Body Temperature and Sleep: Why You Get Hot During Sleep
If your body temperature becomes too hot or too cold at night, you probably won’t sleep well. A number of factors can affect your body temperature during sleep, from your bedding and pajamas to the presence of a medical condition. We explore how sleep affects your body temperature, why body temperature drops during sleep, and how to enjoy cooler sleep if you’re a hot sleeper.
How Does Sleep Affect Your Body Temperature?
Your circadian rhythm, the same internal body clock that regulates your sleep cycles, also regulates your core body temperature. Your core body temperature changes in a fairly predictable pattern over the course of each 24-hour day, decreasing in the evening, which encourages sleep. Once you fall asleep, your body temperature continues falling, facilitating restful sleep. Then, beginning in the morning, it heats back up throughout the day.
Why Does Your Body Temperature Drop When You Sleep?
Across species, mammals tend to experience a lower core body temperature before and during sleep. In addition to signaling to the body that it's time for sleep, experts think this temperature drop might help conserve energy and prompt certain genes to express themselves.
Humans often snuggle up in bedding at night to warm their skin temperatures. Perhaps surprisingly, increasing skin temperature likely helps reduce core body temperature, by diverting blood to the skin. As you sleep, your body continuously adjusts the blood flow to your skin, along with your sweat rate and hormone levels, to keep your body temperature within the best range for sleep.
Why Do I Get Hot While Sleeping?
After learning that your core body temperature drops at night, you may wonder why you tend to feel hot while you're sleeping. There are a few potential explanations.
An Overly Hot Room
A bedroom that is too hot can increase the amount of time you spend in bed awake. Thanks to the training of your circadian rhythm, your body associates heat with wakefulness, so when you get hot, your body is more likely to stay awake.
Once you do fall asleep, heat can affect how much time you spend in each sleep stage. People who sleep in bedrooms that are too hot spend less time in both deep sleep and rapid eye movement (REM) sleep, two stages of sleep that are essential to your emotional and physical wellbeing, muscle and tissue recovery, memory formation, and cognitive performance.
An Overly Humid Room
When your bedroom is too humid, your sweat can’t evaporate as quickly, so you feel hotter. Too high of humidity can also keep you awake and decrease the time you spend in deep and REM sleep once you are asleep.
Your Clothing or Bedding
The clothes you wear to bed, along with your bedding, also contribute to your nighttime heat and humidity levels. Sweating helps your body avoid becoming too hot, so you want to avoid fabrics that interfere with your ability to sweat.
Sleep Disorder or Underlying Condition
Certain health conditions can also affect your body’s ability to regulate temperature, leading to hot sleep. These include sleep disorders, like obstructive sleep apnea. Also, people who have depression don’t experience as much of the decrease in core body temperature that’s supposed to occur before sleep and tend to sweat more at night.
Night sweats in particular have been linked to a number of conditions, including gastroesophageal reflux disease (GERD), diabetes, and obesity. Hormonal changes, such as the decrease in estrogen during menopause, can also lead to hot flashes and disrupted sleep. Finally, certain medications may be associated with night sweats, such as antidepressants, antipsychotics, and anticholinergic drugs, among others.
Tips for Sleeping Cooler
For a cooler night’s sleep, try these tips.
Turn Down Your Thermostat
The ideal bedroom temperature for sleep falls between 66 and 70 degrees Fahrenheit. To stay warm while your room's temperature is in this range, wear pajamas and use bedding that keeps your bed a comfortable temperature.
Wear the Right Clothes to Sleep
The right clothing at night can help you sleep. For example, consider wearing socks to bed. Your feet and hands tend to be colder than the rest of your body. Wearing socks can heat your feet, opening up your blood vessels and enabling your body to maintain a stable core temperature.
As for your pajamas, wool or cotton fabrics could be good choices. In one study of older adults, those who wore wool sleepwear fell asleep faster, and enjoyed better quality sleep, than those who wore cotton or polyester. Their bedrooms were on the warmer side, at 86 degrees Fahrenheit and 50% humidity.
In another study, those who wore wool sleepwear in a bedroom measuring 63 degrees Fahrenheit fell asleep faster than those who wore cotton. When the thermostat was set to 72 degrees Fahrenheit, however, wearing cotton sleepwear was associated with more time spent in deep sleep.
Avoid Strenuous Exercise Before Bed
Don’t do anything too vigorous that may increase your body temperature, like exercise, immediately before bed. Although exercise in general promotes sleep, intense exercise done within 60 minutes of your bedtime can increase the amount of time it takes you to fall asleep, reduce how much you sleep overall, and make you more likely to wake up during the night.
Watch What You Eat and Drink Before Bed
Avoid coffee or spicy meals before sleeping. Caffeine can increase your core body temperature, delaying sleep. Spicy foods can also increase your core body temperature and reduce sleep quality. Plus, both caffeine and spicy foods are associated with heartburn, acid reflux, and indigestion — all of which can make it harder to fall asleep.
Consider Sleeping Alone or Without a Pet
Sharing your bed with a sleep partner, whether human or animal, may increase body heat. If your sleep partner is making your bed too hot, you might want to consider sleeping in separate beds. Although, some people feel the benefits of co-sleeping, such as an increased sense of safety or intimacy, outweigh potential sleep disruption.
However, it’s worth noting that sleeping in the same room as a pet, but not in the same bed, can still provide some benefits. For example, a study of dog owners found that those who had the dog sleep on the floor enjoyed more restful sleep than those who shared their bed.
Change Your Sleep Position
Some research suggests that sleeping on your side may be cooler than sleeping on your back, since you reduce the amount of contact between your body and the mattress.
Talk to Your Doctor
If a medical condition is making you too hot to sleep well, talk with your doctor to learn about potential treatments that may allow you to sleep better. For women experiencing menopause, hormone replacement therapy has proven effective for reducing night sweats and other symptoms. If you’re taking a medication known to affect the body's ability to regulate temperature, such as antidepressants, ask your doctor if there are alternatives you can take instead.
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