Neurofilament light predicts worse nonmotor symptoms and depression in Parkinson's disease

The identification of biomarkers that reflect worse progression of nonmotor symptoms (NMS) in Parkinson's disease (PD) is currently an unmet need. The main aim of this study was to investigate whether cerebrospinal fluid (CSF) and serum neurofilament light (NfL), measured at baseline or longitudinally, can be used to predict the progression of NMS in patients with PD. Baseline and longitudinal NfL levels were measured in the CSF and serum in 392 PD patients and 185 healthy controls from the Parkinson's Progression Marker Initiative. NMS were assessed using several scales, including, but not restricted to, the Movement Disorder Society Unified Parkinson's Disease Rating Scale (MDS-UPDRS) part I, the Geriatric Depression Scale (GDS) and the State-Trait Anxiety Inventory (STAI). The relationship between baseline and longitudinal NfL levels with changes in NMS was assessed using linear mixed effects models (LME) in PD patients. In addition, we compared CSF and serum NfL levels between groups and assessed the relationship between NfL biomarkers with baseline NMS. Finally, to assess the specificity of our findings we ran the previous LME models using other biomarkers such as CSF amyloid-β1–42, total tau, phosphorylated tau181 and total α-synuclein and we also ran the models in healthy controls. Baseline levels and longitudinal changes in serum and CSF NfL predicted worse longitudinal MDS-UPDRS-I and depression scores over time in PD (p