APOE and Alzheimer disease: Furthermore, based on studies reporting a protective effect of the APOE-ε2 allele on AD biomarkers (Kim et al., 2017), we compared PHCB microstructural measures with the APOE-ε2 carriers removed from the sample (5 from the APOE-ε4 noncarrier group, 1 from the APOE-ε4 carrier group).