While non-statistically significant, there was a trend towards faster motor decline in participants with α-syn SAA positive LRRK2 PD compared to those with α-syn SAA negative LRRK2 PD (MDS-UPDRS III points per year: 2.39 (95% confidence interval: 1.86–2.92) vs. 1.76 (0.93–2.60); difference = 0.63 (−0.29 to 1.55, p = 0.18). Here, LRRK2 is linked to Parkinson disease.