Pesticide exposure and diabetes mellitus in a semi-urban Nepali population: a cross-sectional study

Objective Epidemiological studies suggest exposure to pesticides to be related to risk of diabetes mellitus. The objective of the present study was to assess the association between pesticide use and diabetes mellitus in a semi-urban population in Nepal. Methods We conducted a nested cross-sectional study on pesticides and diabetes mellitus in a population-based cohort from the former Lekhnath Municipality, Nepal. 2643 persons were invited, and 2310 persons participated (response rate 87.4%). All participants were tested for fasting plasma glucose. Diabetes mellitus was defined as either fasting plasma glucose (FPG) >= 7.0 mmol/L (126 mg/dL) or self-reported diagnosis of diabetes mellitus. Exposure to pesticides was determined by questionnaire. For the exposed persons, three exposure metrics (years of exposure, weeks of exposure per year and hours of exposure per week) were categorized and used to model exposure-response relationships. Results Although 62% of participants reported to be exposed to pesticides, the frequency and intensity of pesticide usage was low. Contrary to our hypothesis, we found lower odds of diabetes mellitus among persons reporting any pesticide use compared to those reporting no use of pesticides-adjusted odds ratio with 95% CI = 0.68 [0.52; 0.90]. However, we found no clear exposure-response relationships between pesticide exposure and neither diabetes mellitus nor FPG, and few and inconsistent associations were seen between pesticide exposure and symptoms of acute pesticide intoxication. Conclusions The apparently lower odds of diabetes mellitus among pesticide-exposed persons in this population are probably due to residual confounding. Our results do not seem to support an association between pesticide exposure and diabetes mellitus in this low-exposed population dominated by subsistence farmers, although results should be interpreted with caution in light of the study limitations.