GFAP and Alzheimer disease: Finally, in the comparison between DS‐AD and DS‐pAD, based on two studies involving 162 DS‐AD and 109 DS‐pAD individuals, the SMD was 0.42 (95% CI [0.17, 0.67], z = 3.29, Pp = 0.001), indicating a significant difference in plasma GFAP levels between the two groups, with no heterogeneity (I2 = 0%, p = 0.77).