Plasma GFAP levels were positively correlated with age in HCs (r = 0.319, p = 0.002) and PD patients at baseline (r = 0.628, p < 0.001) and 1-year (r = 0.602, p < 0.001) and 2-year (r = 0.665, p < 0.001) follow-ups (Fig. 1D). Here, GFAP is linked to Parkinson disease.