GBA1 and Parkinson disease: The mean age at onset for the individuals who had 2 Parkin mutations (24.0 years) was younger than the age of those who had GBA mutations (P = 0.0009) and those without mutations (P = 0.006) (Table1).The mean duration of PD (± SD) in patients at DBS surgery was 15.0 ± 6.6 years (range, 3.8–38.0 years).