NEFL and Cognitive impairment: Furthermore, FOG progression was associated with higher levels of cognitive impairment-related biomarkers including CSF T-tau (β = 0.00015, p = 0.034, Fig. 2c), P-tau (β = 0.00013, p = 0.038, Fig. 2d), NfL (β = 0.00071, p = 0.009, Fig. 2e) and serum NfL (β = 0.00097, p = 0.004, Fig. 2f).