Elevated plasma neurofilament light chain (NfL) levels are associated with higher disease severity and dementia in patients with Parkinson disease (PD), a study in Neurology suggests.

Patients with PD (n=116), multiple system atrophy (MSA [n=22]), and healthy controls (n=40) were enrolled in this prospective follow-up study. An electrochemiluminescence immunoassay was used to measure participants’ plasma NfL levels.

At baseline and mean 3-year follow-up, patients with PD were assessed for changes in motor and cognition faculties using the Unified Parkinson’s Disease Rating Scale part III motor score and Mini-Mental State Examination score.

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The plasma levels of NfL were higher in patients with MSA than in patients with PD and healthy controls (35.8±6.2 pg/mL vs 17.6±2.8 vs 10.6±2.3 pg/mL, respectively; P <.001). Patients with PD had significantly higher plasma NfL levels if they were in advanced Hoehn-Yahr stage (10.7 ± 6.9 pg/mL for stage I vs 66.8 ± 1.5 for stage V; P <.001).

Plasma levels of NfL increased with increasing severity of cognitive dysfunction (P <.001, 1-way analysis of variance test). There was a modest association between plasma NfL level and Unified Parkinson’s Disease Rating Scale part III score (r, 0.42; 95% CI, 0.46-0.56; P <.001). In the adjusted analysis, higher plasma NfL levels at baseline correlated with higher risks for progression of motor (P =.029) or cognition (P =.015) symptoms.

Limitations of this study included assessment of cognitive function through only Mini-Mental State Examination and inability to confirm the clinical diagnosis of PD and MSA through postmortem studies.

Investigators concluded “this study demonstrated that plasma NfL levels distinguished patients with PD and those with MSA and reflected disease severity in terms of both motor and cognitive functions in patients with PD.” They add, findings from this study suggest “plasma NfL level could serve as a noninvasive, easily accessible biomarker to assess disease severity and to monitor disease progression in PD.”


Lin CH, Li CH, Yang KC, et al. Blood NfL: a biomarker for disease severity and progression in Parkinson disease. Neurology. 2019;93(11):e1104-e1111.