Relation of apolipoprotein E polymorphism to clinically diagnosed Alzheimer's disease in the Korean population

The gene for human apolipoprotoin E (APOE) is found on the long arm of chro mosome 19 (19q13.2) and exists in three common allelic forms, epsilon2, eps ilon3, and epsilon4. The APOE epsilon4 allele is over-represented in Alzhei mer's disease (AD) and is accepted as a genetic risk factor. Some studies r eported a protective effect of the APOE epsilon2 allele for AD. However, th ere are some ethnic variations in the proportion of different APOE alleles and their relationship to AD. We examine the distribution of APOE alleles f rom 30 AD patients and 158 controls in Korea. The control subjects were all cognitively intact unrelated Koreans. The frequencies of APOE alleles in A D patients were 18.3% (epsilon2), 58.3% (epsilon3), and 23.3% (epsilon4). T he corresponding frequencies in controls were 13.3% (epsilon2), 72.5% (epsi lon3), and 14.2% (epsilon4). The frequency of the APOE epsilon2 allele in A D patients was not significantly different from that in controls. When stat istical analysis was conducted after the exclusion of the APOE epsilon2 all ele, the frequency of the APOE epsilon4 allele in AD patients was significa ntly higher than that in controls (P < 0.05). These results support that th e APOE <epsilon>4 allele plays a role as a risk factor for AD in Koreans an d suggest that the APOE epsilon2 allele may not play a protective role in t he development of AD in Koreans.