GFAP and Mental deterioration: For GFAP, as with the other 2 biomarkers, the rate of cognitive decline was not accelerated in non–APOE4 carriers, but it was accelerated among APOE4 carriers per unit increase in GFAP, with an estimate (SD) of −0.12 (0.03) per year (P < .001) (eTable 2 in Supplement 1).