Causal Inference
Paraquat exposure and Parkinson’s Disease: A meta-analysis stratifying by decade of publication, study design, and adjustment for history of head injury Tony Cappello* Tony Cappello Alex Riordan Elizabeth Best Hannah Mazzotta
We conducted a preliminary literature review and meta-analysis of studies that examined the risk of Parkinson’s Disease among persons exposed to paraquat, including residential and occupational settings. Our systematic literature search in PubMed identified 25 published papers that were considered for meta-analyses. Pooled risk estimates or meta-relative risks (meta-RR) were calculated using random effects models, stratifying by overall risk, decade of publication, study design, and adjustment for history of head injury. The overall preliminary meta-RR for Parkinson’s disease was 1.37 (95% CI: 1.21-1.66). For the decade of publication, meta-RRs were only elevated at a level of statistical significance for the earliest decade (1990s) compared to the later decades (2000s, 2010s, and 2020s), reflective of study quality improvement over time. For study design, meta-RRs were only elevated at a level of statistical significance for case-control studies, compared to cohort studies which did not reach statistical significance. When adjusted for history of head injury, the meta-RR was 1.22 (95% CI: 0.74- 2.02) and did not reach a level of statistical significance. Based on this analysis, there is consistent evidence to suggest that exposure to paraquat is not associated with an increased risk of Parkinson’s Disease.