Clinical studies and autopsies have demonstrated that people with heterozygous ApoE ɛ4 are three times more likely to develop AD than noncarriers (odds ratio (OR) = 3.2), and people with a homozygous genotype of ApoE ɛ4/4 are 14 times more likely to develop AD (OR = 14.9) [25]. The gene discussed is APOE; the disease is Alzheimer disease.