For example, the primary genetic risk factor for dementia, the APOE-ε4 allele, is more prevalent among blacks than whites but the relative risk of dementia among carriers of the APOE-ε4 allele is lower for blacks than among whites (Marden, Walter, Tchetgen Tchetgen, Kawachi, & Glymour, 2014), further implicating social and cultural characteristics as key determinants of disparities in dementia. This evidence concerns the gene APOE and dementia.