In Parkinson disease, the NfL concentration in CSF correlated with UPDRS III scores (rs = 0.36, P < 0.001), lower DAT activity in the caudate (rs = −0.21, P = 0.037, poorer cognitive performance in psychomotor speed, language, episodic memory and executive function (rs between −0.30 and 0.39, P < 0.005) and with age (rs = 0.63, P < 0.001). Here, NEFL is linked to Parkinson disease.