Recently, studies performed on AD risk population such as carriers of apolipoprotein E (APOE)-ε4 or rs405509 alleles have detected brain differences between these subjects and control subjects in elderly (Chen et al., 2015; Reiter et al., 2017; Shu et al., 2015) and middle-age population (Cacciaglia et al., 2018; Habib et al., 2017; Mak et al., 2017; ten Kate et al., 2016). The gene discussed is APOE; the disease is Alzheimer disease.