GFAP and Parkinson disease: PD patients with high baseline plasma GFAP also showed a more rapid decline in MoCA scores (β: -0.501, 95% CI [− 0.768 to − 0.234], p < 0.001) and FAB scores (β: − 0.358, 95% CI [− 0.587 to − 0.129], p = 0.002) than those with low baseline plasma GFAP (≤ 48.36 pg/mL; Fig. 3E–F).