The effects of body mass index on age at menopause

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 +/- 1.2y)) or late (n=682; greater than or equal to50y 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 +/- 2.8y). 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 4y 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.