Mediation effect of body mass index on the association between age at menopause and type 2 diabetes mellitus in postmenopausal Chinese women

This study aimed to examine the association between age at menopause and type 2 diabetes mellitus (T2DM), and whether this association is mediated by body mass index (BMI) in postmenopausal Chinese women.This cross-sectional study enrolled 4,279 postmenopausal women. Binary logistic regression was used to estimate the association between age at menopause and T2DM. A multiple linear regression model was used to evaluate the relationships between age at menopause and fasting plasma glucose (FPG), 2-hour postprandial blood glucose (2hPBG), homeostasis model assessment for insulin resistance (HOMA)-IR, and HOMA of ß-cell function (HOMA-ß). Mediation analysis was performed to investigate whether these associations were mediated by BMI.After full adjustment, women with a later age of menopause (>54 y) were more likely to have T2DM (odds ratio =1.401, 95% confidence interval [CI], 1.010-1.945; P = 0.044) than those in the reference group (4453 y). After multiple adjustments, each 1-year increase in the age at onset of menopause was associated with a 0.021 mmol/L increase in FPG (95% CI, 0.004-0.038; P = 0.014), 0.048 mmol/L increase in2hPBG (95% CI, 0.0060.090; P = 0.024), and 1.540 decrease in HOMA-ß (95% CI, -2.386 to -0.695; P < 0.001), but no changes in HOMA-IR. Later age of menopause was associated with overweight/general obesity (odds ratio = 1.416, 95% CI, 1.028-1.950; P = 0.015). BMI partially mediated the association between age at menopause and FPG and 2hPBG, and the proportion of the effect was 5.42% and 7.69%, respectively. Further, BMI suppressed the association between age at menopause and HOMA-ß, and the proportion of the suppressing effect was 9.54%.The later age of menopause was positively related to T2DM. BMI partially mediated the association between age at menopause and glucose status and suppressed the association between age at menopause and HOMA-ß. Prospective studies are warranted to confirm this association.