APOE and hippocampal atrophy: The APOE ɛ 4 allele is a risk factor for lateonset Alzheimier disease (Corder et al. 1993; Meyer et al. 1998; Saunders et al. 1993), hippocampal atrophy (Moffat et al. 2000), and senile plaques (Zubenko et al. 1994).