Metabolite of the pesticide DDT and incident type 2 diabetes in urban India.

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.