GBA1 and Postural instability: The incidence of cognitive impairment and postural instability did not exhibit statistically significant differences among the three CSF SERPIN E1 tertile groups throughout the longitudinal study in PD total cohort, PD WT and PD GBA1. The time interval until 50% of PD patients reached cognitive impairment did not show any statistically significant differences based on the SERPIN E1 tertiles.