Factors related to age at natural menopause: longitudinal analyses from SWAN

Abstract

Early age at the natural final menstrual period (FMP) or menopause has been associated with numerous health outcomes and might be a marker of future ill health. However, potentially modifiable factors affecting age at menopause have not been examined longitudinally in large, diverse populations. The Study of Women's Health Across the Nation (SWAN) followed 3,302 initially premenopausal and early perimenopausal women from 7 US sites and 5 racial/ethnic groups, using annual data (1996-2007) and Cox proportional hazards models to assess the relation of time-invariant and time-varying sociodemographic, lifestyle, and health factors to age at natural FMP. Median age at the FMP was 52.54 years (n = 1,483 observed natural FMPs). Controlling for sociodemographic, lifestyle, and health factors, we found that racial/ethnic groups did not differ in age at the FMP. Higher educational level, prior oral contraceptive use, and higher weight at baseline, as well as being employed, not smoking, consuming alcohol, having less physical activity, and having better self-rated health over follow-up, were significantly associated with later age at the FMP. These results suggest that age at the natural FMP reflects a complex interrelation of health and socioeconomic factors, which could partially explain the relation of late age at FMP to reduced morbidity and mortality.

Keywords: age; education; ethnicity; menopause; oral contraceptives; race; smoking; weight.

Figure 1.

Estimated distribution of age at final menstrual period, unadjusted and adjusted racial/ethnic differences, in the SWAN cohort, 1996–2007. For African Americans, unadjusted median age = 52.17 years and adjusted median age = 52.59 years; for Caucasians, unadjusted median age = 52.88 years and adjusted median age = 52.85 years; for Chinese, unadjusted median age = 52.41 years and adjusted median age = 52.86 years; for Hispanics, unadjusted median age = 50.86 years and adjusted median age = 53.10 years; and for Japanese, unadjusted median age = 53.14 years and adjusted median age = 53.24 years. SWAN, Study of Women's Health Across the Nation.

Figure 2.

Estimated distribution of age at final menstrual period, unadjusted and adjusted differences by educational level, in the SWAN cohort, 1996–2007. For ≤high school, unadjusted median age = 51.53 and adjusted median age = 52.13 years; for some college, unadjusted median age = 52.32 years and adjusted median age = 52.62 years; and for ≥college degree, unadjusted median age = 53.07 years and adjusted median age = 53.05 years. SWAN, Study of Women's Health Across the Nation.

Figure 3.

Estimated distribution of age at final menstrual period, unadjusted and adjusted differences by baseline smoking status, in the SWAN cohort, 1996–2007. For never smokers, unadjusted median age = 52.73 years and adjusted median age = 52.76 years; for ever smokers, unadjusted median age = 52.88 years and adjusted median age = 52.83 years; and for current smokers, unadjusted median age = 51.35 years and adjusted median age = 51.43 years. SWAN, Study of Women's Health Across the Nation.

Figure 4.

Estimated distribution of age at final menstrual period, unadjusted and adjusted differences by oral contraceptive use, in the SWAN cohort, 1996–2007. For never users, unadjusted median age = 52.07 years and adjusted median age = 52.08 years; for ever users, unadjusted median = 52.72 years and adjusted median age = 52.75 years. SWAN, Study of Women's Health Across the Nation.