APOE and Alzheimer disease: Given the complexity of this region on chromosome 19, including LD across multiple genes, plentiful polymorphisms, and the strong APOE ε2/ε3/ε4 effect on AD risk, alternative approaches focused on haplotype analysis of this region are proposed to uncover novel variants that influence AD independent of APOE. 45Our analysis of stratifying samples according to specific genotypic/haplotypic backgrounds provides another approach in the discovery of polymorphisms that may influence AD risk under a specific genomic context.