Objective: This study aimed to investigate the association between exposure to pesticides and the risk of Parkinson’s disease (PD).

Background: PD is the second most common neurodegenerative disease worldwide with a prevalence of over 8.5 million. Among neurological disorders, it appears to be the fastest growing in prevalence and disability. In recent years, studies have sought to identify modifiable risk factors for PD, as evidence-based interventions could help to prevent PD incidence on a global scale. One such risk factor is pesticide exposure. Pesticides such as paraquat and rotenone have been found to increase the risk of PD through oxidative stress or mitochondrial complex I inhibition, respectively, in animal models.

Method: This study identified studies investigating pesticide exposure and risk of incident PD published between 1980 to 2022 from PubMed, Embase and Web of Science. Data extraction was performed and cross-screened by two independent researchers. A meta-analysis for log relative risk (RR) was performed using the R package metafor. Study population representativeness, confounder adjustment, and exposure and case ascertainment methods were tracked and included as potential bias covariates in the model.

Results: 77 papers were included in total, with 37 from PubMed and 40 from Embase and Web of Science. Pesticide exposure was assessed through questionnaires as “ever used” (36.4%) or classified according to duration of use (48.9%), serum levels of specific pesticides were measured in 14.3% of the studies. The majority of studies assessed PD diagnosis through examination by specialists (62.3%), while 20.8% reviewed medical notes, and 5.19% were self-reported. Preliminary results show that the overall RR estimate for exposure to any pesticide was 1.93 (95% CI 1.64-2.26). In sub-analyses by pesticide type, herbicide overall RR estimate was 1.37 (95% CI 1.01-1.86), insecticide was 2.57 (95% CI 1.69-3.74), fungicide was 2.45 (95% CI 1.37-4.37), organochlorine was 1.99 (95% CI 1.03-3.88) and organophosphorus was 2.32 (95% CI 1.11-4.85).

Conclusion: This study strongly supports a positive association between pesticide exposure and risk of incident PD. Further studies on specific pesticides associated with higher PD risk could be helpful in guiding policymakers globally to implement regulations on the use of these pesticides and play a role in PD prevention.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/systematic-review-and-meta-analysis-of-pesticide-exposure-and-the-risk-of-parkinsons-disease/