The most robust findings have demonstrated that the presence of the APOE ε4 allele imparts a genetic risk for the development of cognitive impairment, specifically that related to AD and vascular dementia (Allan and Ebmeier, 2011; Pink et al., 2015; Chen et al., 2016a; Jiang et al., 2016; Liu et al., 2016). The gene discussed is APOE; the disease is Alzheimer disease.