APOE and hippocampal atrophy: Furthermore, we noticed that plasma Aβ42/Aβ40 and cortical Aβ burden independently predicted longitudinal hippocampal atrophy in APOE-ε4 carriers but not in APOE-ε4 non-carriers, suggesting that APOE-ε4 allele may probably modulate the association between Aβ pathology and hippocampal atrophy.