APOE and Alzheimer disease: Variants at amino acids 112 and 158 were classified as APOE2 (ε2, 112C/158C), APOE3 [ε3, 112C/158R; ε3r, 112R/158C (Seripa et al., 2011, , 2007)], and APOE4 (ε4, 112R/158R) (Fig. 3B), among which APOE ε2/ε3r have been shown or are presumed (Seripa et al., 2007, 2011) to confer lower risk of AD than APOE4.