Genetic analysis will be conducted by experienced laboratory technicians under the supervision of Dr. Joachim Hallmayer. Blood for genotyping (approximately 6ccs) will be drawn at the time of eligibility screening, after informed consent. Genotype results will not be released to participants. Blood samples will be labeled with a unique subject identifier known only to the PI's research staff. Genotyping for APOE will be the primary genetic analysis and will be performed according to the restriction isotyping protocol of Hixson and Vernier. Two observers blind to clinical status of the individuals will carry out assignment of genotypes.