High plasma neurofilament light (NFL) levels correlate with poor cognition in Parkinson disease (PD) and Alzheimer disease (AD) and may represent a blood-based biomarker of cognitive decline, according to study results published in Scientific Reports.

In the current study, levels of plasma NFL in 119 patients with AD, 23 with Parkinson disease dementia (PDD), 26 with nondemented Parkinson disease (PDND), 56 with mild cognitive impairment (MCI), and 59 healthy control (HC) participants with normal cognitive functioning were measured and compared to illuminate the associations between plasma NFL levels and cognitive decline. Patients were also given physical exams, clinical interviews, brain imaging, and neuropsychological evaluations to assess cognition, dementia, and disease severity.

On all cognitive tests, patients in the AD group scored significantly worse than patients in the MCI, HC, and NDPD groups and significantly worse on measures of category verbal fluency and delayed recall than patients in the PDD group (P <.001 for all).

Mean plasma NFL was 32.9±25.5 pg/mL in the AD group, 23.3±10.8 pg/mL in the PDD group, 15.4±9.9 pg/mL in the NDPD group, 20.0±7.3 pg/mL in the MCI group, and 17.8±6.4 pg/mL for the HC participants and increased with age across all subgroups (Pearson r =0.427; P <.001).

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After adjusting for sex, age, education, and carrier status for the apolipoprotein E (APOE)-ε4 allele, patients with AD had higher levels of plasma NFL than HC participants, patients with NDPD, and patients with MCI (P <.001 for all) or PDD (P =.047). Levels of plasma NFL were not correlated with motor symptoms in PD, as measured by the Unified Parkinson’s disease rating scale for NDPD (r =−0.069, P =.743 ), PDD (r =0.056; P =.81), and for all (Pearson r =0.177; P =.238).

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Study investigators concluded that “[h]igh plasma NFL correlated with poor cognition both in AD and PD patients, but not with motor symptoms in PD patients. Plasma NFL may represent a biomarker of cognitive decline in AD and PD, with greater specificity for AD.”


Lin YS, Lee WJ, Wang SJ, Fuh JL. Levels of plasma neurofilament light chain and cognitive function in patients with Alzheimer or Parkinson disease. Sci Rep. 2018;8(1):17368.