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November 8, 2000

Race, Parity, and Gestational Diabetes as Risk Factors for Type 2 Diabetes Mellitus—Reply

Author Affiliations

Stephen J.LurieMD, PhD, Senior EditorIndividualAuthorPhil B.FontanarosaMD, Executive Deputy EditorIndividualAuthor

JAMA. 2000;284(18):2318-2319. doi:10.1001/jama.284.18.2317

In Reply: Although the association between high parity and increased risk of type 2 diabetes is not well established, it is certainly a plausible confounder because the effect of pregnancy may mediate this relationship through increased weight gain or other independent pathways. In our study, women were asked to report their number of pregnancies. Additional analyses indicate that this variable was associated both with race and diabetes risk. In general, African American women had a greater number of pregnancies than white women (median numbers of pregnancies were 4 for African American women and 3 for white women). In addition, greater parity was associated with higher diabetes risk (RR, 1.12 per pregnancy; 95% confidence interval [CI], 1.09-1.15).

However, the confounding by number of pregnancies of the association between race and diabetes risk was minimal. After adjusting for age, family history of diabetes, education, body mass index, waist-to-hip ratio, sports-related and non–sports-related leisure time activity, smoking, alcohol use, dietary energy intake, and number of pregnancies, the RR of type 2 diabetes associated with being African American was 1.81 (95% CI, 1.50-2.17) and the risk of type 2 diabetes associated with additional pregnancy was 1.02 (95% CI, 0.99-1.06). In our previous analysis in which number of pregnancies was not included in the regression model (Model 5 in Table 3 of our article), the RR of type 2 diabetes associated with being African American was similar at 1.85 (95% CI, 1.55-2.21).

As Drs Kahn and Williamson state, gestational diabetes is associated with increased diabetes risk, thus the differential exclusion of gestational diabetes with respect to race may result in higher diabetes incidence among African American women. Unfortunately, our study did not collect specific information on gestational diabetes.