APOE and Alzheimer disease: Compared with neurologically healthy individuals without the ApoE ε4 allele, those with the ApoE ε4 allele show greater regional CBF reductions in the brain, making it vulnerable to pathological alterations in AD (Thambisetty et al., 2010; Hollands et al., 2017) and presbycusis (Kurniawan et al., 2012).