APOE and Alzheimer disease: For example, APOE ε4 carriers have shown greater hippocampal atrophy than non-carriers in AD patients, cognitively normal elderly, and healthy young adults (Alexopoulos et al. 2011a, b; den Heijer et al. 2002; O’Dwyer et al. 2012; Pievani et al. 2011).