GFAP and Parkinson disease: As shown in Figure 1, there were no significant differences between the PD and HC groups in the plasma levels of α-syn, Aβ42, Aβ42/Aβ40 ratio, T-tau, and p-tau181 levels; however, the PD patients had a significantly higher level of GFAP (99.583 ± 42.135 pg/mL vs. 70.415 ± 19.539 pg/mL, p < 0.001) than the HCs, and the PDD patients had lower T-tau levels (0.863 ± 0.451 pg/mL vs. 1.294 ± 0.595 pg/mL, p < 0.01) than the PD-NC patients.