Sex, apolipoprotein E ε4 status, and hippocampal volume in mild cognitive impairment

Background: Subjects with mild cognitive impairment (MCI) have been shown to have reduced hippocampal volumes relative to normal elderly control subjects. The presence of the apolipoprotein E ε4 (APOE*E4) allele has been associated with greater hippocampal atrophy in women than in men with Alzheimer disease. This relationship has not been demonstrated in MCI. Objective: To examine the relationship between APOE genotype and hippocampal volume in men and women with MCI. Design: This study evaluated MCI in 193 subjects (86 women and 107 men) participating in a multicenter clinical trial, all of whom underwent magnetic resonance imaging at their baseline visit. We evaluated the association among the number of APOE*E4 alleles, memory performance, and hippocampal volume in men and women with tests of means and multiple linear regressions. Results: Compared with MCI subjects with no APOE*E4 alleles, women with 1 or 2 APOE*E4 alleles were found to have significantly reduced hippocampal volume, whereas men only showed a significant reduction in hippocampal volume when carrying 2 APOE*E4 alleles. Worsening of performance on a delayed word recall task (Alzheimer's Disease Assessment Scale cognitive subscale) showed an identical pattern in association with APOE*E4 allele dose and sex. Furthermore, when controlling for memory performance on delayed word recall, the APOE*E4 effect on hippocampal volumes was attenuated in men, but remained significant in women. Conclusion: The APOE*E4 genotype status appears to have a greater deleterious effect on gross hippocampal pathology and memory performance in women than in men.