GFAP and Alzheimer disease: Plasma concentration of GFAP was significantly higher in AD converters compared with CU across all three time points (estimated difference (standard error), p-value) at 10 years prior to symptom onset (35.88 pg/mL (9.04), p < 0.0001), 5 years prior to symptom onset (31.53 pg/mL (9.33), p = 0.0008) and at symptom onset (46.09 pg/mL (11.01), p < 0.0001).