Reproductive hormones and obesity: 9 years of observation from the Study of Women's Health Across the Nation

Abstract

The effect of change in reproductive hormones and menopause on incident obesity (body mass index > or =30 kg/m(2)) and severe obesity (body mass index > or =35 kg/m(2)) was evaluated over 9 years in 3,260 US women recruited in the multiethnic Study of Women's Health Across the Nation in 1996-1997. After 9 years, cumulative incidences of obesity and severe obesity reached 21.8% and 12.3%, respectively. In multivariate analysis, hormone changes, chronic health conditions, lower physical activity, race/ethnicity, and age were significantly associated with incident obesity and/or severe obesity. The odds of incident severe obesity increased with surgical menopause (odds ratio (OR) = 5.07, 95% confidence interval (CI): 2.29, 11.20; P < 0.001) and initiation of hormone therapy prior to 12 months of amenorrhea (OR = 2.94, 95% CI: 1.14, 7.58; P = 0.03). Predictors of obesity included an increase in free androgen index (OR = 1.37, 95% CI: 1.12, 1.68; P = 0.002) and a decrease in sex hormone-binding globulin (OR = 0.60, 95% CI: 0.45, 0.80; P = 0.0005). Similar results were found for severe obesity. Obesity rates varied by race, but no hormone-by-race interactions were observed. These longitudinal data demonstrate that higher androgens, lower sex hormone-binding globulin, surgical menopause, and early hormone therapy use predict incident obesity and/or severe obesity in a multiracial cohort of women transitioning into menopause.

Figure 1.

Prevalence of obesity at baseline by ethnicity in the Study of Women's Health Across the Nation, United States, 1996–1997.

Figure 2.

Kaplan-Meier curves showing freedom from A) incident obesity and B) severe obesity over a 9-year period in the Study of Women's Health Across the Nation, United States, 1996–2006.