Studies have found that in general, the optimal temperature for sleep is quite cool, around 60 to 68 degrees Fahrenheit. Temperatures that fall too far below or above this range can lead to restlessness.
Temperatures in this range help facilitate the decrease in core body temperature that in turn initiates sleepiness. A growing number of studies are finding that temperature regulation plays a role in many cases of chronic insomnia.
Researchers have shown, for example, that insomniacs tend to have a warmer core body temperature than normal sleepers just before bed, which leads to heightened arousal and a struggle to fall asleep.
For troubled sleepers, a cool room and a hot-water bottle placed at the feet, which rapidly dilates blood vessels and therefore actually helps lower core temperature, can push the internal thermostat to a better setting.