The strength of this study is that we analyzed how APOE-ε4 allele modulates the cross-sectional and longitudinal associations between plasma Aβ42/Aβ40, Aβ PET and white matter lesions as well as their prediction of longitudinal hippocampal atrophy and cognitive decline simultaneously up to 9 years’ follow-up. This evidence concerns the gene APOE and hippocampal atrophy.