We estimated the hazard and predictive performance of six AD blood biomarkers for incident all-cause and AD dementia—the ratio of amyloid-β 42 to amyloid-β 40 and levels of tau phosphorylated at T217 (p-tau217), tau phosphorylated at T181 (p-tau181), total tau, neurofilament light chain (NfL), and glial fibrillary acidic protein (GFAP)—in a cohort of 2,148 dementia-free older adults from Sweden, who were followed for up to 16 years. This evidence concerns the gene GFAP and Alzheimer disease.