Hot Flushes Last Much Longer Than Expected in Practice

Laurie Barclay, MD

April 26, 2011

April 26, 2011 — Hot flushes may last longer than generally accepted in clinical practice, according to the results of a study reported in the May issue of Obstetrics & Gynecology.

"The peak prevalence of hot flushes occurs approximately 1 year after menopause, but the overall duration of hot flushes is unclear," write Ellen W. Freeman, PhD, from the Department of Obstetrics/Gynecology, the Center for Clinical Epidemiology and Biostatistics, and the Center for Research in Reproduction and Women's Health at the School of Medicine, University of Pennsylvania in Philadelphia, and colleagues. "Clinical guidelines indicate that the duration of hot flushes for most women is approximately 6 months to 2 years....Increased information about the duration of hot flushes is important for the clinical management of menopausal symptoms."

The goal of the study was to estimate the duration of moderate to severe menopausal hot flushes and to identify potential risk factors for hot flush duration among women monitored for 13 years in the Penn Ovarian Aging Study. In-person interviews at 9- to 12-month intervals allowed assessment of hot flushes. Duration of moderate to severe hot flushes, as estimated by survival analysis in 259 women, was the main study endpoint, and a secondary analysis was performed in 349 women who reported any hot flushes. The investigators evaluated menopausal stage, age, race, reproductive hormone levels, body mass index (BMI), and current smoking as potential risk factors associated with hot flushes.

The median duration of moderate to severe hot flushes was 10.2 years. Duration was strongly associated with menopausal stage at onset, with median duration of more than 11.57 years for hot flushes starting near entry into the menopause transition, 7.35 years (95% confidence interval [CI], 4.94 - 8.89; P < .001) for those beginning in the early transition stage, and 3.84 years (95% CI, 1.77 - 5.52; P < .001) for those beginning in the late transition to postmenopausal stages.

The most common ages at onset of moderate to severe hot flushes were 45 to 49 years, with median duration of 8.1 years (95% CI, 5.12 - 9.28). Compared with white women, African American women had a longer duration of hot flushes, according to results of an adjusted analysis.

"The median duration of hot flushes considerably exceeded the timeframe that is generally accepted in clinical practice," the study authors write. "The identified risk factors, particularly menopausal stage, race, and BMI, are important to consider in individualizing treatment and evaluating the risk-to-benefit ratio of hormones and other therapies."

Limitations of this study include possible overestimation of hot flush duration because of use of survival analysis, possible causation of some hot flushes by conditions other than menopause, exclusion of women using hormone therapy, and lack of generalizability to other populations.

"Perhaps treatments for vasomotor symptoms should be targeted more commonly to younger, irregularly menstruating women, although it must be recognized that traditional hormone therapy may not be the ideal choice for this population given, for example, the problems of breakthrough bleeding and the need for contraception," the study authors conclude. "Other treatments for hot flushes need to be evaluated, particularly for women who have not reached menopause. Race and body mass index also significantly influenced the duration of hot flushes and are important considerations in individualizing treatment, particularly when the predicted duration of hot flushes is substantially longer than the length of hormone therapy that is currently recommended."

The National Institutes of Health supported this study. Dr. Freeman has received research support from Forest Laboratories, Inc, Wyeth, Pfizer, and Xanodyne Pharmaceuticals. She has also received honoraria for consulting and presentations from Wyeth, Forest Laboratories, Inc, Pherin Pharmaceuticals, and Bayer HealthCare. The other study authors have disclosed no relevant financial relationships.

Obstet Gynecol. 2011;117:1095-1104. Abstract

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