APOE and Alzheimer disease: Gene mutations in encoding the amyloid precursor protein (APP) or presenilin (PS1 and PS2) [26], and more recently the APOE gene with the E4 allele mutation, have been identified as significant genetic susceptibility predictors for AD [27], with over 60% of individuals affected by AD carrying the APOE4 variant compared to a much lower prevalence of 25–27% in the general population.