Effect of aging, menopause, and age at natural menopause on the trend in body mass index: a 15-year population-based cohort

Abstract

Objective: To observe the effects of menopause, age at natural menopause (ANM), and aging on the trend in body mass index (BMI).

Design: Prospective cohort with a 15-year follow-up of 929 women. Data obtained from the Tehran Lipid and Glucose Study.

Setting: Not applicable.

Intervention(s): none.

Participant(s): Of women participating in the Tehran Lipid and Glucose Study, 929 who were reproductive during the study and menopaused at the last follow-up were included. Anthropometric data were measured repeatedly every 3 years, and the trend in BMI, associated with menopause and ANM, was tested using the generalized estimating equation.

Main outcome measure(s): Body mass index in each follow-up session.

Result(s): The adjusted model of the generalized estimating equation illustrates that BMI increases by age (β = 0.16) and menopausal status (β = 1.11). It also shows that women with higher ANM experienced a decreasing BMI (β = -0.03) compared with women with lower ANM. The interaction term of menopause and time (menopause × time) has a negative effect on BMI; that is, the usual increase in BMI after menopause is attenuated by time. (β = -0.4, 95% confidence interval -0.6, -0.3).

Conclusion(s): Menopause and aging are independently correlated with increasing BMI. The trend in BMI, however, depends on the ANM of study participants: women with higher ANM than mean ANM of our population (i.e., 49 years) face a decreasing BMI compared with those with lower ANM.

Keywords: Age at natural menopause; body mass index; interrupted time series analysis; menopause; obesity.