Changes in body composition in women over six years at midlife: Ovarian and chronological aging

Context: Understanding the menopause association with body weight is important because excess weight increases risk for stroke, incident cardiovascular disease, cardiovascular mortality, and all-cause mortality among the middle-aged. Objective: The objective of this study was to examine chronological age and ovarian age and consider how these could influence body size and composition in midlife women. Design and Setting: The Study of Women's Health Across the Nation is a longitudinal, community-based study. This report uses data from the Michigan Study of Women's Health Across the Nation site. Participants: Participants were 543 premenopausal or early peri-menopausal African-American and Caucasian women aged 42-52 yr at baseline examination. Main Outcome Measures: Waist circumference, fat mass and skeletal muscle mass, from bioelectrical impedance, were assessed in seven annual serial measures. Annual FSH values were assayed by ELISA. The final menstrual period was defined retrospectively after 12 months of amenorrhea. Results: There was an absolute cumulative 6-yr increase in fat mass of 3.4 kg and a 6-yr decrease in skeletal muscle mass of approximately 0.23 kg. There was an absolute cumulative 6-yr increase of approximately 5.7 cm in waist circumference. The logFSH change was positively correlated with log(fat mass) change. Waist circumference increased over the time period, but 1 yr after final menstrual period, the rate of increase slowed. Fat mass continued to increase with no change in rate. Conclusions: Both time (chronological aging) and ovarian aging contributed to substantial changes in body composition (fat and skeletal muscle mass) and waist circumference. These changes have important ramifications for establishing a metabolic environment that can be healthy or unhealthy.