There was a slower, although not statistically significant, rate of cognitive decline for carriers with a LRRK2 G2019S variation compared with individuals with idiopathic PD for LRRK2 PD alone (B [SE], 0.10 [0.06] points/y; P = .08) and LRRK2/GBA PD (B [SE], 0.08 [0.05] points/y; P = .12). Here, LRRK2 is linked to Parkinson disease.