Outcome Data

Summary statistics from the largest, published PD GWAS meta‐analysis involving 26,035 PD cases and 403,190 controls of European ancestry were used as the outcome data for the primary analysis. Recruitment and genotyping quality‐control procedures were described in the original report.11

A newer PD GWAS included a total of 37,688 cases, 1,417,791 controls, and 18,618 “proxy cases” from the UKB (individuals that reported having a parent with PD).2 However, there was substantial overlap in control subjects between each of the UKB exposures and the Nalls and colleagues 2019 meta‐analysis, which can, in turn, lead to bias in causal effect estimates. For this reason, we repeated the analyses using only 5,851 clinically diagnosed PD cases and 5,866 matched controls as the outcome, after excluding UKB samples and self‐reported PD cases and controls. Finally, we used an earlier PD GWAS as the outcome that included 13,708 cases and 95,282 controls.12