Hot flashes and awakenings among midlife women

For most women, the menopause is accompanied by hot flashes and sleep problems. Although hot flashes reportedly wake women from sleep, in the few studies that have used objective measures of both sleep and hot flashes, links between hot flashes and nocturnal awakening have been inconsistent. In a well-characterized cohort of midlife women, we examined the association between objectively assessed hot flashes and actigraphically defined wake from sleep. We hypothesized that wake episodes would be more likely during an objective hot flash relative to minutes without a hot flash.

Peri- and postmenopausal midlife women underwent simultaneous objective measurement of hot flashes (sternal skin conductance) and sleep (actigraphy) over 24 hours in the home. The likelihood of waking in the minutes during the hot flash relative to the minutes preceding the hot flash was compared using generalized estimating equations.

We studied 168 women with at least one objective nocturnal hot flash and actigraphy data. Actigraphy-assessed wake episodes were concurrent with 78% of the objective hot flashes. We found an increased likelihood of wake in the minutes during the objective hot flash (0 to +5 min: OR [95% CI] = 5.31 (4.46 to 6.33); p < .0001) relative to the minutes preceding it (-10 to -1 min). The increased likelihood of wake occurred irrespective of whether the women reported the objective hot flash.

Among these women who underwent objective measurement of sleep and hot flashes, nocturnal wakefulness was observed with the majority of hot flashes.