Menopausal Hot Flashes Flourish During First Half of Night

Menopausal hot flashes are more likely to fire off during the first half of the night, especially if the room is warm, investigators reported here.

People are more easily roused in the first half of the sleep cycle, whereas rapid eye movement (REM) activity suppresses thermoregulatory signals in the second half of the night, reported researchers at the North American Menopause Society meeting here.

If women experience these symptoms, turning the thermostat down to approximately 64° F for the first half of the night may reduce hot flashes and improve sleep quality, said Robert R. Freedman, Ph.D., of Wayne State in Detroit.

"Hot flash-induced sleep disturbances appear in the first half of the night, when REM sleep is less frequent and is not there to suppress hot flashes," said Dr. Freedman. "Some reports of poor sleep during Menopause may be due to normal aging, but misattributed to hot flashes," he said.

Dr. Freedman and co-investigators conducted their study because despite epidemiologic studies and the widely held belief that hot flashes disturb sleep, they had evidence to the contrary from a recent sleep study of their own. In a probability sample of 589 subjects, the team found that postmenopausal women actually have better sleep quality than premenopausal women.

A hot flash is a brief feeling of intense warmth and sweating. Hot flashes commonly occur in women around the time of Menopause.

Researchers do not know exactly what causes hot flashes. Current theories suggest hot flashes are due to a Menopause related drop in the body's level of female hormones called estrogens. This drop affects the hypothalamus, an area of the brain that regulates body temperature. In a hot flash, the hypothalamus seems to sense that your body is too hot even when it is not, and tells the body to release the excess heat. One way the body does this is to widen (dilate) blood vessels, particularly those near the skin of the head, face, neck and chest. Once the blood vessels return to normal size, you feel cool again.

Therefore, they launched a sleep study involving 36 women. Eighteen were postmenopausal and experiencing vasomotor symptoms; six were postmenopausal and asymptomatic, and 12 were still cycling. On four consecutive nights the investigators varied the ambient room temperature. The first night, the adaptation night, the temperature was 23° C (73° F) or neutral. On subsequent nights, the room was randomly 18° C (64° F) or cool, 23° C (73° F) or neutral, or 30° C (87° F) warm.