Warm Socks May Help You Sleep

(MSNBC, September 1 1999)  Wearing socks to bed may not excite your partner, but it just might help you fall asleep. A researcher says people with chronically cold feet and hands might drift off faster if they warm their feet with socks or a hot water bottle, and maybe even wear mittens.

Scientists at Switzerland's Chronobiology and Sleep Laboratory, at the Psychiatric University Clinic, said Wednesday that warm feet and hands induce sleep quickly. The heat from mittens and socks dilates blood vessels that help to redistribute body heat. This together with the release of hormones like melatonin, which helps control the sleeping cycle, is part of the sleep routine.

Most people go through the process naturally and wouldn't need socks or a water bottle to help them sleep. The key step to opening the gates of sleep is that your feet and hands get hot and you lose heat to the outside. That has to happen before you go to sleep, said Anna Wirz-Justice, who led the Swiss research.

People who go to bed with cold feet will have a much more difficult time than those who help themselves with hot water bottles and bed socks, but they have to have a cool bedroom or they won't be able to lose the heat to the outside. That's the key mixture. The release of heat is one of many steps in the body that lead to sleep. The body clock must be at the right time and melatonin must be rising.

Wirz-Justice and colleagues didn't directly test whether socks or water bottles promote sleep. But they did analyze data from 18 healthy young men who participated in sleep studies. The results suggest that blood vessel dilation in the hands and feet in late evening, and resulting heat loss, are key to falling asleep.

According to a letter to the science journal Nature, the researchers measured blood flow and heat loss and timed how long it took a group of healthy young men to fall asleep. The men were given melatonin, heavy meals and exposed to bright lights to see how it would influence sleep. The researchers found that the more the blood vessels were dilated in the late evening, the shorter it took to fall asleep.

The Associated Press and Reuters contributed to this report.