The Science of Sleeping Hot Vs. Cold

For approximately five- to eight-hours daily, we get to lay our worries to rest, crawl into a cool bed, close our eyes and drift into a restful sleep. In a perfect world, we’d wake when our alarm went off and not a minute before. Unfortunately, the reality is that many of us have woken up in the middle of the night feeling overheated with our once-cool sheets stuck to our legs with sweat. How is it possible that the sleep environment that once brought us so much joy, can bring such discomfort in a matter of hours?

The Relationship Between Body Temperature and Sleep

As human beings, we are able to maintain our inner core body temperature and skin in a process called thermoregulation. Our core body temperature is regulated by our circadian rhythm, or internal clock. During the daytime, core body temperature tends to be high and outer temperature low for optimal alertness. While the hours tick on throughout the workday, our body temperatures gradually start to fall and heat loss increases until, eventually, the time to curl into bed and under the covers arrives, the National Sleep Foundation says.

While sleeping, our core body temperature continues to fall by 1- to 2-degrees Fahrenheit as less energy is used to maintain body temperature, according to the Division of Sleep Medicine at Harvard Medical School. During non-REM sleep, a period in which the body repairs and regenerates tissues, core temperature reduces at a slightly lower level before falling to its lowest point about 90 minutes into the night, during REM sleep.  

Throughout this process, the blankets that once protected us from a cool night’s breeze may start to trap every bit of discarded body heat until we wake up, irritable and overheated. Not only is this uncomfortable, but it can significantly affect our ability to obtain quality shut eye and hinder daytime energy levels. So, what’s the solution? Before you crank up the air conditioner or toss out your favorite bedspread, read these simple solutions.

Optimal Temperature for Sleep

Like Goldilocks, the ideal temperature for sleep is not too hot or too cold, but just right. The National Sleep Foundation suggests a bedroom temperature of between 60- and 67-degrees Fahrenheit for optimal sleep, because it mimics the body’s internal temperature drop. Meanwhile, more extreme temperatures, including those above 75 degrees Fahrenheit and below 54 degrees will disrupt sleep.

“The key is to find a good balance between hot and cold to support your body in moving you from alertness to sleep and then back to alertness when you are ready to wake up,” Sleep Doctor Michael Breus says.

Tips for Staying Cool

It turns out that our inkling to seek out the cool side of the pillow is more than just a personal preference. Research shows that cooler body temperatures lead to more deep sleep. While consistently turning the thermostat between 60- and 67-degrees Fahrenheit may not be a plausible solution in setting up your ideal sleep environment, there are a variety of other factors to help you sleep cool. 

• Take a Bath: One great way to cool down and destress before bedtime is by taking a bath around 60 to 90 minutes before bed. While soaking in warm water may sound counterproductive to the cooling process, it helps by first raising body temperature while you’re in the tub to lowering it when you eventually get out.
• Wear Light Pajamas and Socks: Breathable fabrics, including cotton, linen and silk, are best for sleeping. If your feet are cold, complete your pajama ensemble with a pair of cashmere socks or cover your feet with an extra blanket in bed. Warming up your feet causes vasodilation, the dilation of blood vessels, which redistribute heat throughout the body and signal to the brain that it’s bedtime.
• Cover Yourself in the Right Bedding: While we venture through the summer months, it’s safe to pull out a lightweight comforter or blanket and forgo the winter quilt. Avoid synthetic fabrics and high-thread-count sheets, which trap heat and moisture, and instead opt for cotton or bamboo sheets and comforters.
•  Invest in a Good Mattress: Visible signs of overuse, such as sagging or damage, stiffness and aches in your back, and constant feelings of overheating can be signs that your once-trusty mattress needs replacing. With Ananda’s Pearl and Gel Infused Memory Foam Mattress, cooling gel is infused into the top and second layers of the mattress to neutralize varying temperatures throughout the night while you sleep. Additionally, cooling Tencel is woven into the mattress cover for even more temperature control.

If you’ve ever wondered why your temperature seems to run hotter at night, you’re not alone. Don’t let the nightmare of overheating wake you from your deepest stages of sleep. Achieve a cooler, more restful sleep through the right external temperatures, breathable bedding and clothing, and a reliable mattress to help you fall asleep faster and stay asleep longer.