APOE and Alzheimer disease: The ApoE-ε4 allele, on the other hand, is associated with decreased Aβ1–42 and higher tau and p-tau in the CSF and increased cerebral amyloid deposition across the AD spectrum (Tapiola et al., 2000; Morris et al., 2010; Leoni, 2011; Risacher and Saykin, 2013; Wildsmith et al., 2013; Kanekiyo et al., 2014).