Body mass index in mid-life women: relative influence of menopause, hormone use, and ethnicity.
OBJECTIVE: To assess the relative influence of menopausal status and hormone use on body mass index (BMI) among a multiethnic sample of mid-life women. DESIGN: Cross-sectional telephone survey conducted at seven sites where each site targeted an ethnic minority group and Caucasians as part of Study of Women's Health Across the Nation (SWAN). SUBJECTS: A total of 7181 Caucasians, 3949 African-Americans, 1660 Hispanics, 562 Chinese Americans, and 803 Japanese Americans between ages of 40 and 55 y residing in or near Boston, Chicago, Detroit, Los Angeles, Newark, NJ, Oakland, CA, and Pittsburgh, PA. MEASUREMENTS: Self-reported BMI based on weight in kg divided by height in m(2) menopausal status, physical inactivity, postmenopausal hormone use, ethnicity, and age in years. RESULTS: Compared to premenopausal women (covariate adjusted M=27.3), women reporting a surgical menopause (M=28.2) or being in the perimenopausal transition (M=27.7 for early and 27.9 for late perimenopause) had higher BMI. Women reporting a natural menopause (M=27.4) did not have a higher BMI than premenopausal women, after adjusting for chronological age and other covariates. Hormone use was associated with lower BMI (M=26.5 vs 27.3). A comparison of effect sizes showed that menopausal status (F=13.1), followed by chronological age (F=24.0), were the least powerful predictors of BMI, whereas the more powerful predictors were physical activity level (F=1377.1) and ethnicity (F=400.5). CONCLUSIONS: The menopausal transition affects body mass index in mid-life, but the effect is small relative to other influences. Interventions to increase physical activity are highly recommended to prevent increases in adiposity common in mid-life.