α-Synuclein Strain Dynamics Correlate with Cognitive Shifts in Parkinson's Disease.

α-Synuclein (α-syn) strains can serve as discriminators between Parkinson's disease (PD) from other α-synucleinopathies. The relationship between α-syn strain dynamics and clinical performance as patients transition from normal cognition (NC) to cognitive impairment (CI) is not known. Here, we show that the biophysical properties and neurotoxicity of α-syn strains change as PD cognitive status transitions from NC to mild cognitive impairment (PD-MCI) and dementia (PD-D). Both cross-sectional and longitudinal analyses reveal distinct α-syn strains in PD patients correlating to their level of cognitive impairment. This study presents evidence that individuals with PD have different α-syn strains that change in accordance with their cognitive status and highlights the potential of α-syn strain dynamics to guide future diagnosis, management, and stratification of PD patients.