SLC6A3 and Parkinson disease: We analyzed 7 years of motor, non-motor, and cognitive assessments and 5 years of dopamine transporter imaging along with baseline α-syn SAA results from 564 PPMI participants (n=332 sporadic PD, 162 LRRK2 PD, and 70 GBA PD) using linear mixed-effects models, adjusted for potential confounders, to test whether baseline α-syn SAA positivity (n=315 sporadic PD, 111 LRRK2 PD, and 66 GBA PD) was associated with PD progression.