APOE and Alzheimer disease: While most studies examining genetic risk for sporadic AD focus on APOE genotype, some have assessed polygenic risk scores beyond APOE based on case-control data from large-scale genome-wide association studies (GWAS) (Lambert et al., 2013), and found that genetic variants associated with elevated AD risk also influence brain structure (Sabuncu et al., 2012) and cognitive function (Marioni et al., 2017).