SNCA and Parkinson disease: CSF α-synuclein, Aβ40, and Aβ42 were significantly lower in PD patients as compared with HC subjects (F(1,6) = 8.35; p = 0.01, F(1,6) = 14.69; p = 0.001, and F(1,6) = 4.61; p = 0.05, respectively).