GBA1 and Parkinson disease: Of those participants that reported a family history of PD (i.e., first degree relative), the frequency of LRRK2 p.G2019S carriers was 1.66% (SE = 0.07%), 0.08% (SE = 0.05%) for GBA1 p.N409S, 0.05% (SE = 0.01%) for dual carriers, and 97.50% (SE = 0.08%) for noncarriers.