Those who sleep in cold environments, meanwhile, tend to fare better. A study of people with a sleep disorder found that they slept longer in temperatures of 61 degrees Fahrenheit versus 75 degrees. The cold-sleepers were also more alert the next morning. The basic physiology is that your body undergoes several changes at night to ease you into sleep: Your core and brain temperatures decrease, and both blood sugar and heart rate drop. Keeping a bedroom hot essentially fights against this process. Insomnia has even been linked to a basic malfunctioning of the body’s heat-regulation cycles—meaning some cases could be a disorder of body temperature.

In light of this physiology, sleep experts unanimously suggest keeping your bedroom cooler than the standard daytime temperature of your home. There is no universally accepted temperature that is the correct one, but various medical entities have suggested ideal temperature ranges. The most common recommendation, cited by places like the Cleveland Clinic and the National Sleep Foundation, is 60 to 67 degrees Fahrenheit. Within that range, experts vary. A neurologist in Virginia told Health.com that the magic number is 65. Others have advised an upper limit of 64.