GFAP and Mental deterioration: Although previous studies have shown that lower Aβ42/40 and higher ptau-181 [18, 22], NfL [7, 17], and GFAP [17] in blood are associated with increased rate of cognitive decline [23], the vast majority of studies connecting these blood biomarkers to cognitive function have been cross-sectional [7, 17, 19, 24].