GFAP and Alzheimer disease: This is consistent with previous studies that merely simplified the Alzheimer’s continuum into distinct stages [13, 17, 33], and we further reinforced the notion that plasma GFAP may be an early and sensitive biomarker of AD pathological changes by assessing the alterations of biomarkers as a function of CSF Aβ42/Aβ40 and p-tau181.