Introduction:
Recent studies report an association between early age at menarche and risk of type 2 diabetes (T2D). However, information in young women is limited to self-reported diabetes in primarily white populations. We explored the association of age at menarche and clinically-defined T2D among young black and white women (mean age 25 at baseline) in the Coronary Artery Risk Development in Young Adults (CARDIA) cohort.
Hypothesis:
We assessed the hypothesis that the rate for T2D will decrease with each 1 year increase in age at menarche.
Methods:
Our analysis included 1,258 white and 1,341 black women (total=2,599) who participated in CARDIA during 1985-2006. We used Cox proportional hazards models to estimate hazard ratios (HR) for T2D (yes/no as determined at clinic visits) by continuous age at menarche. We excluded women with diabetes at baseline, missing age at menarche, or menarche <8 or >18 years. T2D was defined cumulatively from baseline among non-pregnant women as fasting blood glucose ≥ 126 mg/dl, A1C ≥ 6.5%, 2-hour oral glucose tolerance ≥ 200 mg/dl, or use of diabetes medication. Adjusted models included race (except race stratified models) and parental history of diabetes, as well as baseline age, education, and BMI as covariates.
Results:
Mean age at menarche was 12.6 years (SD=1.5; black=12.5, white=12.7). We identified 176 cases of T2D over 20 years of follow-up (cumulative incidence=6.8%). Among all women, the rate for T2D decreased by 16% for each 1 year increase in menarche age (
Table 1
); we found no evidence of nonlinearity. HRs remained protective, but no longer statistically significant after adjustment for BMI. HRs were lower for white women compared to black women, although a test for race by menarche age interaction was not significant (p=0.26).
Conclusions:
We found evidence to support the hypothesis that early menarche increases the rate for T2D among young women. Higher baseline BMI among women with earlier menarche appears to attenuate the association of age at menarche and future glucose metabolism.
Table 1.
Hazard Ratio (HR) of Type 2 Diabetes for Each One Year Increase in Age at Menarche in the CARDIA Study, 1985-2006
Crude
Model 1
Model 2
# T2D
HR
95% CI
HR
95% CI
HR
95% CI
All Women
176
0.84
0.76, 0.93
0.88
0.79, 0.98
0.94
0.85, 1.04
White
46
0.78
0.64, 0.96
0.83
0.68, 1.02
0.93
0.76, 1.16
Black
130
0.90
0.80, 1.01
0.90
0.80, 1.02
0.96
0.85, 1.08
Model 1: adjusted for race (except for race-stratified models), family history of diabetes, baseline age, and participant level of education at baseline (<HS, HS, >HS) Model 2: adjusted for variables in Model 1 plus baseline BMI
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