LRRK2 and Parkinson disease: Specifically, among participants without the LRRK2 G2019S variation, participants with GBA experienced faster decline compared with those without (ie, GBA PD vs idiopathic PD), but among participants with LRRK2 G2019S, those with a GBA variation had no difference compared with participants without a GBA variation (ie, LRRK2/GBA PD vs LRRK2 PD).