Background: Previous epidemiological studies, largely conducted in high-income countries and cross-sectional, have suggested a relatively strong association between exposure to dichlorodiphenyldichloroethylene (DDE), a metabolite of the pesticide dichlorodiphenyltrichloroethane (DDT), and type 2 diabetes. DDT is widely used in India and the prevalence of type 2 diabetes there is increasing, but the association between these factors has not been explored to date. Objective: The objective was to estimate the association of the p,p′ isomer of DDE with incident type 2 diabetes in India. Methods: A nested case-control study was conducted in a representative prospective cohort of adults from two cities in India. Participants were enrolled in 2010–11 (n = 12,271) and followed for annual assessment of chronic diseases including type 2 diabetes. Baseline plasma samples from incident cases of diabetes (n = 193) and sex-city-matched controls (n = 323) were selected for analysis of p,p-DDE. Odds ratios (OR) and 95% confidence intervals (CI) were estimated using conditional logistic regression. Results: At baseline, cases had higher p,p-DDE concentrations: geometric mean (95% CI) 330 (273–399) ng/g lipid compared to 223 (189–262) ng/g lipid among controls. Delhi participants had higher p,p-DDE concentrations: 579 (521–643) ng/g lipid compared to 122 (102–145) ng/g lipid in Chennai. In unadjusted models, being in the highest versus lowest quartile of p,p-DDE was associated with a more than doubling of the odds of diabetes: unadjusted OR (95% CI), 2.30 (1.19, 4.43). However, this effect was no longer significant after adjustment for age: adjusted (95% CI), 0.97 (0.46, 2.06). Discussion: Results suggest that levels of p,p′-DDE in Delhi are exceptionally high, but we did not observe a significant association between p,p-DDE and incident type 2 diabetes. As this is the first study to evaluate this association in India, more studies are needed to inform our understanding of the association in this context, including potential routes of exposure. Keywords: Asia, Endocrine disruptors, Pesticides, Diabetes mellitus, Case-control studies
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