NEFL and Parkinson disease: In patients with PD, those classified as N+ had worse scores on the MoCA-J, Hoehn and Yahr, MDS-UPDRS III, SCOPA-AUT, BDI-II, PDQ-39, and QUIP scales than patients classified as N−, suggesting that plasma NfL levels are related to cognitive function, and motor and non-motor symptoms.