By Lily Hautau, CNN
(CNN) — If you have ever tossed and turned under heavy blankets, you’ve felt firsthand how being too warm can wreck your sleep.
“Temperature is one of the most underappreciated factors in sleep,” said Joseph Dzierzewski, senior vice president of research and scientific affairs at the National Sleep Foundation. “We often hear about light, screens and stress, but even modest changes in temperature and airflow can influence how quickly you fall asleep and how deeply you stay asleep.”
Your core body temperature naturally drops by about 1 to 2 degrees Fahrenheit (about 0.6 to 1 degree Celsius) to fall asleep, he said, and if that cooling process is disrupted even slightly, sleep can become more fragmented and less restorative.
The most important thing is creating what Dzierzewski calls a comfortable sleep microclimate, in which your body isn’t trapping heat between your skin, sleepwear and bedding.
“For some people, that may mean sleeping naked or with minimal clothing; for others, lightweight, moisture-wicking fabrics work well,” he said. The goal is to feel comfortable and secure while helping your body cool naturally.
For Brian Diva Cox in Portland, Oregon, that microclimate is easiest to achieve without pajamas. He said sleeping naked became a nightly habit in his teens and, while it’s more occasional now as an adult, he still does it when he wants to prioritize comfort and recovery — especially on nights when time is short.
“I wake up refreshed,” he said, adding that he invariably has energy and his smart watch’s sleep chart shows his improved sleep quality the next day.
Whether you ditch your pajamas or simply switch to lighter layers, reducing insulation can make it easier for your body to release heat. Interestingly, Dzierzewski also noted that warming the hands and feet before bed can help the body release heat more efficiently and fall asleep faster. For people who naturally have cold extremities, keeping them comfortably warm during sleep can also help maintain more stable sleep.
How much moisture there is in the air matters, too.
“High humidity limits your body’s ability to cool itself through sweat,” he said, so using breathable, moisture-wicking materials in mattresses, bedding and sleepwear can all help your body offload the heat.
Keeping a cooler room, typically around 60 to 67 degrees Fahrenheit (around 15 to 19 degrees Celsius) with good airflow, can also support that process, Dzierzewski explained. Be flexible with those temperatures, since comfort can vary by person and people who sleep hot or are experiencing hormonal changes tend to prefer the cooler end of the range.
Finally, it’s not just about setting a cooler temperature — it’s about keeping it consistent through the night. Big swings can trigger middle-of-the-night wake-ups if you start overheating.
Cooler temps can also impact sperm production
Temperature doesn’t just affect sleep quality — it plays a role in reproductive health, too.
“The testes are outside the body for a reason — optimal sperm production requires temperatures a few degrees below core body temp,” said CNN contributor Dr. Jamin Brahmbhatt, a urologist and robotic surgeon with Orlando Health. That’s why what you choose to wear or not wear to bed can matter.
Brahmbhatt, who is also an assistant professor at the University of Central Florida’s College of Medicine, also referenced a large Harvard University study that showed men who wore boxers had higher sperm concentration than those who wore formfitting styles. But he said the key factor is not the tightness itself, but the heat.
“Tight underwear traps heat against the body,” he explained, echoing the same reasoning arou