SAN DIEGO — Postmenopausal women with severe vasomotor symptoms show a circadian rhythm of hot flashes that peaks in the late afternoon and early evening hours, results from a small study showed.
“A lot of women complain about frequency of hot flashes at night,” Lauren Drogos said in an interview after her poster presentation at the annual meeting of the North American Menopause Society. “But we found that women were having the least frequent amount of hot flashes at night.”
For the study, Ms. Drogos and her associates evaluated baseline data from a trial of 29 postmenopausal women who had at least 35 hot flashes per week and were enrolled in a clinical trial comparing the efficacy of hormone therapy, black cohosh, and red clover for menopausal symptoms and cognition.
The women wore ambulatory sternal skin conductance monitors, which recorded their hot flashes over a 24-hour period. Hot flashes were defined as a greater than 2-micromho increase in skin conductance within 30 seconds. The women also kept a diary of perceived hot flashes.
In an effort to reduce the interindividual variability in the time of hot flashes for study participants on different sleep/wake schedules, the researchers normalized the data to each woman's wake time. The mean age of the study participants was 53 years, 61% were African American, 36% were white, and the rest were Asian American.
The women had an average of 19 hot flashes during the 24-hour monitoring period, including 14 during waking hours and 5 during sleeping hours, reported Ms. Drogos, a graduate student in the department of psychology at the University of Illinois at Chicago. “There was a broad peak of hot flash frequency, extending from late afternoon to evening hours, and a nadir that roughly corresponded to the time of the sleep episode,” the investigators wrote in their poster.
Ms. Drogos acknowledged certain limitations of the study, including its small sample size and the fact that it focused on highly symptomatic women.
She reported no conflicts of interest.