In female subjects aged 76 years (corresponding to the median age in the female sample) or younger, those carrying the APOE4 allele have a ten-fold increased AD risk than non APOE4 carriers, while within subjects older than 76 years, those carrying the APOE4 allele have a nearly four-fold increased AD risk than non-APOE4 carriers. The gene discussed is APOE; the disease is Alzheimer disease.