The effects of body mass index on age at menopause

Abstract

Objective: We examined which of body mass index (BMI, kg/m(2)), serum cholesterol (mg/dl), or systolic blood pressure (SBP, mm Hg) affected age at natural menopause.

Design: A population-based follow-up program.

Methods: We determined the age at natural menopause in 1136 women followed biennially since their first examination in 1958-1959 through the 16th examination in 1988-1989. Four-hundred and ninety-three naturally menopausal women were classified into three groups by BMI, serum cholesterol and SBP measurement levels at age 40 or 41 y: the upper 25%, middle 50%, and lower 25%. We then studied whether there was a difference in age at menopause among the three groups thus classified. The 1136 natural menopausal women were also classified as early (n=454; 45-49 y at menopause (48.3+/-1.2 y)) or late (n=682; >or=50 y at menopause (52.3+/-1.6 y)) menopausal and compared for premenopausal trends in BMI, serum cholesterol and SBP in the early and late menopausal women by means of a longitudinal data analysis model.

Results: When women were classified into the three groups based on a BMI that was measured at 40 or 41 y, age at menopause in the upper 25% (50.4+/-2.8 y) was significantly higher (P<0.05) than that in the lower 25% (49.7+/-2.8 y). The entire premenopausal trend in BMI in late menopausal women shifted upward compared to that in early menopausal women. On the other hand, the premenopausal trend more than 4 y before menopause in serum cholesterol and the entire premenopausal trend in SBP in late menopausal women were identical to those in early menopausal women.

Conclusion: Among the variables studied, only BMI is related to age at menopause, and the greater the BMI, the later the age at menopause.