As many as 85% of menopausal women experience hot flashes. During a hot flash, women have sensations of heat that may or may not involve sweating. Hot flashes can occur during the night, and they have been attributed to sleep disturbances and insomnia . But many other factors associated with age—including anxiety, sleep apnea, chronic pain, and generally poor health—can also affect sleep, so the exact link between hot flashes and insomnia has been unclear.

A new study in the June 26, 2006 issue of Archives of Internal Medicine studied a group of almost 1,000 women and found that as the severity of hot flashes increased, the likelihood of having chronic insomnia increased.

About the Study

This study involved 982 women ages 35-65. The women completed phone interviews to assess their insomnia symptoms (eg, problems falling or staying asleep, dissatisfaction with sleep quality), overall health, and menopausal status. The women were classified as being premenopausal (still having regular menstrual cycles), perimenopausal (irregular menstrual cycles, but at least one in the previous year), or postmenopausal (no menstrual bleeding in the past year). They reported whether they were having hot flashes at least three days per week during the past month, and if so, if they were usually mild, moderate, or severe. Mild hot flashes did not involve sweating, moderate ones involved sweating but did not interrupt daytime activities, and severe ones involved sweating and caused the women to stop their activities.

About one-third of the women reported having hot flashes, including 13% in the premenopausal group, 79% in the perimenopausal group, and 39% in the postmenopausal group. Even after controlling for other factors thought to affect sleep, severe hot flashes were significantly associated with symptoms and a diagnosis of chronic insomnia. The likelihood of having insomnia increased with hot flash severity—81% of the women, who reported severe hot flashes, had symptoms of chronic insomnia. Poor health, chronic pain, and sleep apnea were also associated with chronic insomnia.

These findings were limited because the women were studied at one point in time rather than over a period of time, making it impossible for researchers to determine if hot flashes actually cause insomnia. Also, severity of hot flashes and insomnia symptoms were based on self-report, which is subject to error.

How Does This Affect You?

This study suggests that women who experience severe hot flashes are more likely to have insomnia. Other studies have shown that the risk of having insomnia increases as women reach menopause.

Not getting enough sleep at night can be frustrating, and it can leave you tired and irritable—unable to function as you normally would. If you are having hot flashes severe enough to interfere with your sleep, talk with your doctor. He or she can recommend lifestyle modifications (eg, keeping your bedroom cool; avoiding spicy foods, alcohol, and caffeine) and/or medications that may ease your hot flashes and allow you to get the sleep you need.