GFAP and Alzheimer disease: In secondary analyses to test whether plasma concentrations of the AD biomarkers differed by APOE genotype within the AD converter and CU groups (Supplementary Table 4), we observed that plasma GFAP levels were significantly higher in APOE ε4 carriers compared to non-carriers among AD converters 5 years prior to symptom onset (P= 0.0149) with a similar trend at the onset of symptoms (P = 0.0731).