To quantify the association between paraquat exposure and Parkinson’s disease (PD) risk in U.S.-based studies using meta-analytic 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.

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) but low by I² (0.8%). 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.

Current U.S.-based epidemiologic evidence does not demonstrate a statistically significant association between paraquat exposure and PD risk. Despite low I², the wide prediction interval and significant Q test suggest variability across studies.