The frequency of the APOE-e4/e4 genotype among registrants is higher than in the general population, at 4.47%, and the APOE-e4 allele frequency is 20.4%; among the 3,456 registrants asked about whether they had a family history of dementia or Alzheimer disease, 70.1% said yes. Here, APOE is linked to early-onset autosomal dominant Alzheimer disease.