Evidence supporting a direct association between the Apolipoprotein E ε4 allele (APOE4) and the risk for age-related cognitive decline is growing; APOE4 status (i.e., having 1 or 2 ε4 alleles vs. none) is among the most well-established genetic risk factors for late onset Alzheimer’s disease (AD) and for age-related cognitive decline [1–22]. The gene discussed is APOE; the disease is early-onset autosomal dominant Alzheimer disease.