Imapct [sic] of Pesticide Exposure on Motor Function and Mortality Among Patients with Parkinson's Disease in Southern Brazil

BACKGROUND: Multiple studies have suggested that various pesticides are associated with a higher risk of developing Parkinson's disease (PD). However, few studies have examined the impact of pesticide exposure on motor impairment and the risk of mortality among patients with PD. This study takes place in the context of growing pesticide use in Brazil as well as many other low- and middle-income countries around the world. OBJECTIVE: This study examines whether occupational pesticide exposure influences motor impairment and the risk of mortality among patients with PD in Southern Brazil, when accounting for socioeconomic status, disease-specific factors, nicotine exposure, and caffeine exposure. METHODS: 150 patients with idiopathic PD in Porto Alegre, Brazil were enrolled from 2008-2013 and followed until 2019. In addition to undergoing a detailed neurologic evaluation, patients completed surveys regarding environmental exposures. 105 of these patients also completed an additional survey regarding socioeconomic factors. The primary outcomes were whether occupational pesticide exposure was associated with motor impairment (as measured by linear regression with UPDRS-III score) and mortality (as determined by the log-rank test and Kaplan-Meier testing). Secondary analyses included models that accounted for relevant socioeconomic and disease specific characteristics (multiple linear regression for motor function, and multivariate cox proportionate hazards regressions for mortality). RESULTS: Of the 150 patients in this prospective cohort, 20 (13.3%) reported a history of occupational pesticide exposure, with an average duration of exposure of 14.3 years (SD = 10.6, median = 10). In the univariate analysis, occupational pesticide exposure was associated with a 16.10 point increase in the UPDRS-III (motor function) score (95% CI: [7.11, 25.02], p < 0.001). Similarly, in the multiple linear regression which controlled for several socioeconomic and disease-related covariates, pesticide exposure was associated with a 16.84 point increase in the UPDRS-III score (95% CI: [8.84, 24.85], p < 0.001). Patients with occupational pesticide exposure were more than two times as likely to die than their unexposed PD counterparts (HR = 2.32, 95% CI [1.15, 4.66], p = 0.22). This was significant when controlling for smoking history, caffeine intake, and socioeconomic factors such as historical monthly income, education, and a history of working predominately in agricultural professions. Patients with 10 or more years of occupational pesticide exposure had a significantly elevated risk of mortality (HR = 2.81, 95% CI [1.17, 6.73], p = 0.02), in contrast to patients with fewer than 10 years of exposure. CONCLUSION: In addition to providing a broad overview of the socioeconomic breakdown of a contemporary cohort of patients with PD in South America, this study implicates occupational pesticide exposure as an independent risk factor for poor motor function and mortality among patients with PD when controlling for disease-specific and socioeconomic confounding factors. This is especially important in the Brazilian market, and perhaps in other developing countries, where new pesticides continue to be introduced without the corresponding research output necessary to understand the impact on human health.