APOE and Alzheimer disease: One potential mechanism is via accumulation and/or clearance of amyloid-β (Aβ, a hallmark of AD) from the brain because ApoE4 has been associated with greater Aβ burden (Strittmatter et al., 1993; Ye et al., 2005; Drzezga et al., 2009) and ApoE2 with lower Aβ burden (Jiang et al., 2008; Morris et al., 2010).