Association of Favorable Cerebrospinal Fluid Markers With Reversion of Mild Cognitive Impairment Due to Parkinson's Disease.

Objective: Cognitive impairment is a common nonmotor symptom among individuals with Parkinson's disease (PD). Although cognitive impairment generally develops progressively, individuals with PD-associated mild cognitive impairment (PD-MCI) may revert to being cognitively normal (CN), which is referred to as PD-MCI reversion. Previous studies are inconsistent in whether PD-MCI reverters are at greater risk for PD-MCI recurrence relative to CN individuals. Even less is known about how PD-MCI reverters compare with CN individuals or PD-MCI nonreverters in terms of neurodegenerative biomarkers. The authors examined group differences (CN, PD-MCI reversion, and PD-MCI nonreversion) in cerebrospinal fluid (CSF) markers of Alzheimer's disease (AD), including amyloid beta, tau (total [t-tau] and phosphorylated [p-tau]), and alpha-synuclein.

Methods: Data from the longitudinal international multisite Parkinson Progression Marker Initiative were used. Participants were newly diagnosed as having PD (N=430) and completed a battery of neurocognitive assessments at baseline and annual follow-ups for up to 5 years. Participants were classified as CN, PD-MCI reverters, or PD-MCI nonreverters on the basis of the first two neurocognitive assessments.

Results: The PD-MCI nonreversion group had greater p-tau:amyloid beta and t-tau:amyloid beta ratios relative to the PD-MCI reversion group. The CN and PD-MCI reversion groups did not significantly differ in any of the CSF markers.

Conclusions: PD-MCI reverters may have a more favorable trajectory in terms of AD pathology relative to PD-MCI nonreverters. Future studies are needed to verify whether PD-MCI reversion may represent an intermediate prognostic group between CN individuals and those with MCI nonreversion.