Title: Paraquat Exposure and Parkinson’s Disease Risk in the United States: A Meta-analysis of Epidemiologic Studies (P3-16.005)
Authors: Jamir Pitton Rissardo, Ana Leticia Fornari Caprara, Ian M. Walker
Conference: 2026 AAN, Chicago, IL
Objective
To quantify the association between paraquat exposure and Parkinson’s disease (PD) risk in U.S.-based studies using meta-analytic methods.
Background
Paraquat, a widely used herbicide, has been implicated as a potential environmental risk factor for PD. While numerous studies have examined this association globally, regulatory and exposure patterns differ by region. Clarifying the risk in U.S. populations is critical for public health and policy decisions.
Design/Methods
We conducted a systematic review and meta-analysis of 19 U.S.-based studies assessing paraquat exposure and PD risk. Binary outcome data were synthesized using the Mantel-Haenszel method under fixed- and random-effects models. Between-study variance (τ²) was estimated using the DerSimonian-Laird method, and heterogeneity was assessed with Cochran’s Q and I². Subgroup analyses were performed for occupational, environmental, and mixed exposure categories. Publication bias was evaluated using Egger’s, Begg’s, and Thompson-Sharp tests, as well as trim-and-fill analysis.
Results
The fixed-effects model yielded an effect size of −0.01 (95% CI: −0.09 to 0.07; p = 0.76), while the random-effects model showed −0.07 (95% CI: −0.30 to 0.15; p = 0.52). The prediction interval ranged from −0.91 to 0.76, indicating substantial uncertainty in true effects across populations. Heterogeneity was statistically significant by Q test (Q = 83.9, p < 0.001). Subgroup analyses revealed no significant associations for occupational exposure (OR 0.99; 95% CI, 0.88–1.12), environmental exposure (OR 0.98; 95% CI, 0.87–1.10), or mixed exposure (OR 3.46; 95% CI, 0.38–31.55), with all confidence intervals crossing unity. No evidence of publication bias was detected by Egger’s (p = 0.696), Begg’s (p = 0.916), or trim-and-fill methods.
Conclusions
Current U.S.-based epidemiologic evidence does not demonstrate a statistically significant association between paraquat exposure and PD risk. The wide prediction interval and significant Q test suggest variability across studies.
Citation
Rissardo JP, Caprara ALF, Walker IM. Paraquat Exposure and Parkinson’s Disease Risk in the United States: A Meta-analysis of Epidemiologic Studies (P3-16.005). Neurology 2026;106(11_suppl):620. doi: 10.1212/WNL.0000000000213021.
Figure 1. Forest plot of U.S. studies on paraquat exposure and Parkinson’s disease showing pooled odds ratios near unity across occupational, environmental, and mixed exposures, with substantial heterogeneity and wide prediction interval.
Figure 2. Funnel plot with confidence contours showing study distribution around pooled effect estimates; symmetry and formal tests indicate no significant publication bias in U.S. paraquat–PD studies.