Tony Roy is among the 30% of American adults with insomnia-related problems. “I can go to sleep, but I wake up three or four hours later,” says Roy, a 51-year-old philosophy professor at California State University, San Bernardino. When he sought help at the nearby Sleep Disorders Center at Loma Linda University Medical Center, he got advice that had never occurred to him: Pay close attention to your bedroom temperature.

For years, Roy had followed his energy-conscious wife’s suggestion to lower the thermostat. “It was quite cold in our house,” he says. “We used to sleep with the thermostat set at about 60. I used lots of blankets.”

Not enough, it turned out. The very first night Roy followed his doctor’s suggestion to push the heat up to a more comfortable 68 degrees, he got a much better night’s sleep. “I was able to go back to sleep when I did wake up,” he says.