Although genome-wide approaches (e.g., the use of SNP arrays or massive parallel sequencing) have identified more than 25 additional loci that are associated with AD, these loci have only moderate effect sizes with odds ratios ranging from 1.1 to 1.5, whereas the odds ratio for APOE ε4 versus ε3 is estimated at 3.7 [14]. Here, APOE is linked to Alzheimer disease.