In the estimated trajectories, onsets of DAT decline in the GBA and LRRK2 PD groups started at a similar age (GBA PD 50.0 vs. LRRK2 PD 50.3 years), however, GBA PD patients showed a rapid decrease in estimated SBRs and earlier onset of motor symptom compared to the LRRK2 PD and sPD groups (SBR reduction during premotor phase; GBA PD 0.19/year, LRRK2 PD 0.16/year, sPD 0.15/year). The gene discussed is SLC6A3; the disease is Parkinson disease.