Risk factors for the development of AD dementia include advanced age; female sex [34,35], presence of the APOE ε4 allele, encoding isoform apolipoprotein 4 (ApoE4); other genetic and epigenetic variations [36,37,38]; brain injury [39]; and environmental factors and stressors [40,41], including a low level of education [42,43] and other lifestyle factors [44]; infections [45]; cardiovascular disease [46,47]; type 2 diabetes mellitus [48,49]; and other comorbid metabolic diseases [50]. Here, APOE is linked to diabetes mellitus.