APOE and cerebral amyloid angiopathy: Moreover, the ε4 allele is linked to cerebral amyloid angiopathy, which often leads to an increased number of microbleeds shown on brain MRI.13,14 Exploring the pathways from APOE ε4 to cognitive decline or dementia mediated by these neuroimaging biomarkers can further clarify the pathophysiologic processes of APOE ε4.