APOE and Mental deterioration: ApoE ε4 allele(s) status has also been associated with disease progression from MCI to AD, such that the onset of AD could be reported 8–16 years earlier among individuals with the ApoE ε4 allele(s), compared to non-ApoE ε4 allele carriers (Liu et al., 2013), indicating as well even faster rates of cognitive decline (Martins et al., 2005).