RESUMEN
OBJECTIVE: The menopausal transition results in a progressive decrease in circulating estrogen levels. Experimental evidence in rodents has indicated that estrogen depletion leads to a reduction of energy expenditure and physical activity. It is unclear whether treatment with estrogen therapy increases physical activity level in postmenopausal women. METHODS: A total of 27,327 postmenopausal women aged 50-79 years enrolled in the Women's Health Initiative randomized double-blind trials of menopausal hormone therapy. Self-reported leisure-time physical activity at baseline, and years 1, 3, and 6 was quantified as metabolic equivalents (MET)-h/wk. In each trial, comparison between intervention and placebo groups of changes in physical activity levels from baseline to follow-up assessment was examined using linear regression models. RESULTS: In the CEE-alone trial, the increase in MET-h/wk was greater in the placebo group compared with the intervention group at years 3 ( P = 0.002) and 6 ( P < 0.001). Similar results were observed when analyses were restricted to women who maintained an adherence rate ≥80% during the trial or who were physically active at baseline. In the CEE + MPA trial, the primary analyses did not show significant differences between groups, but the increase of MET-h/wk was greater in the placebo group compared with the intervention group at year 3 ( P = 0.004) among women with an adherence rate ≥80%. CONCLUSIONS: The results from this clinical trial do not support the hypothesis that estrogen treatment increases physical activity among postmenopausal women.