GFAP and Parkinson disease: In light of the above, this study aimed to compare six biomarkers (α-syn, Aβ42, Aβ42/Aβ40 ratio, T-tau, p-tau181, and GFAP) using plasma and neuronal EVs between HC and different levels of cognitive function in patients with PD in order to find a biomarker that can provide meaningful information about movement or cognitive severity.