The Surprisingly Easy Body-Temperature Trick That Helps You Sleep Deeper, According to Doctors

Sleep can be a fickle thing: sometimes we succeed in staying off our phones and properly winding down before bed, but still feel groggy the next morning. If you’ve got your bedtime routine down and still aren’t feeling rested, there might be one key variable you’re overlooking: temperature. 

According to sleep doctors, the trick to improving sleep is not to bundle up and get cozy, but to cool the body down before bed. Keep reading to hear from experts about the importance of deep sleep, the critical role temperature plays in this type of sleep, and their best tips for enhancing sleep quality by being mindful of temperature. 

The Importance of Deep Sleep

We all know sleep is important, but why is deep sleep so crucial to feeling rested? “Deep sleep is the most restorative stage of sleep,” says Dr. Andrea Matsumura, board-certified sleep medicine physician. “It’s when the brain clears waste, the body repairs tissues, and key hormones that affect energy, metabolism, and immunity are regulated. Without enough deep sleep, people often wake feeling unrefreshed, even if they got a full night’s sleep.” According to the Sleep Foundation, we spend the most time in deep sleep during the first half of the night. This is why properly setting the stage to fall and stay asleep is key to feeling rested.

How Temperature Is Connected to the Sleep Cycle

According to Dr. Raj Dasgupta, chief medical advisor at Sleepopolis, body temperature and the sleep/wake cycle are linked via your circadian rhythm, which controls your body temperature. “[Your core body temperature] drops before and while you sleep (lowest in early morning) to promote rest, then rises during the day, peaking in the afternoon/evening, signaling alertness and activity,” he says. That drop in core body temperature prior to sleep serves as a biological cue to wind down by affecting a number of processes. “Cooler temperatures during sleep, and especially the natural drop in core body temperature before sleep, strongly promote the parasympathetic nervous system, which signals relaxation, reduces stress hormones like cortisol, calms the heart by slowing the heart rate, and enhances deeper and restorative sleep stages like slow-wave sleep and REM sleep.” 

Dr. Matsumura notes that lowering core body temperature by cooling your sleep environment helps the body enter deep sleep more easily. “Anything that gently accelerates or enhances this nighttime cooling process can help the body transition into sleep more efficiently,” she says. “A cooler environment helps the body reach that lower temperature, which supports deeper, more continuous slow-wave sleep. If the room is too warm, sleep can be lighter or more fragmented.”

5 Tips for Using Temperature to Improve Deep Sleep

Place a cool, damp towel on your forehead.

Sleep scientists support using one of the oldest sleep tricks in the book. “A cold towel can help initiate that temperature drop more quickly,” Dr. Matsumura says. Drape a cool, damp towel or washcloth over your forehead and eyes to cool down as you drift off.

Take a warm bath or shower.

It may seem counterintuitive, but a properly-timed warm bath or shower can gently ease the body temperature down before bed. “Warm baths and showers prior to sleep work by temporarily raising body temperature and then allowing heat to escape through your skin after you exit the tub, which lowers core temperature to help induce relaxation and sleepiness,” Dr. Dasgupta says. According to the Sleep Foundation, the ideal time for a warm bath or shower is at least one hour before sleeping. 

Sleep with socks on.

In a similar vein, keeping your feet warm at night can facilitate cooling in the rest of the body. “Warming the feet causes blood vessels in the feet to dilate, which allows heat to move from the core to the extremities," explains Dr. Matsumura. The cooler your core body, the stronger the signal to your brain that it’s time to sleep. 

Improve airflow.

Make sure you’re not trapping heat in your room and bedding even after you’ve turned down the thermostat. Both Dr. Matsumura and Dr. Raj recommend using a fan or opening a window to promote air circulation in your bedroom. “If you’re using heavy blankets or memory foam mattresses that trap heat, consider swapping them out for lighter, breathable alternatives,” Dr. Matsumura suggests. “Invest in moisture-wicking, breathable bedding—think bamboo or cotton sheets.”

Similarly, Dr. Dasgupta suggests using “a cooling pillow or mattress topper with temperature-regulating technology.” He specifically warns against heavy blankets over your torso early in the night, since the majority of deep sleep occurs during the first few hours of sleeping.