The aim and scope of this study are to determine if there is a relationship between LBP found in the 1.21–1.25 g/mL density fraction of plasma in AD patients compared with age-matched cognitively normal controls, and whether this relationship is influenced by APOE genotype by examining the differences between individuals with the two most prevalent APOE genotypes, APOE3/E3 and APOE3/E4. This evidence concerns the gene APOE and Alzheimer disease.