APOE and diabetes mellitus: Several genetic and environmental risk factors have been demonstrated in the occurrence and progression of AD, such as the presence of the Apolipoprotein E (APOE) ε4 allele (Corder et al., 1993), AD-risk single nucleotide polymorphisms (SNPs) (Lambert et al., 2013), advancing age (Amieva et al., 2004), female sex (Li et al., 2016), low education attainment (Solfrizzi et al., 2004), diabetes mellitus (DM), and hypertension (Kryscio et al., 2013).