APOE and Alzheimer disease: The ε4 allele of the APOE gene encoding the apolipoprotein E (apoE) protein strongly influences AD risk and age of onset [8, 9]; risk increases significantly in individuals carrying one copy (ε2/ε4, OR 2.6; ε3/ε4, OR 3.2) or two copies (ε4/ε4, OR 14.9) of the ε4 allele compared to individuals with an ε3/ε3 genotype [10, 11].