Apolipoprotein e polymorphism in elderly East Africans

Current advances have shown the apolipoprotein E (APOE)-ε4 allele to be highly associated with late-onset familial and sporadic Alzheimer's disease (AD) in Western populations. The association of APOE allele frequencies and dementia remain unknown in populations from developing countries. We recently initiated a project to examine APOE frequencies in non-demented and demented elderly East Africans. Blood DNA collected from two hospital-based populations showed that the APOE allele frequencies in a group of non-demented 67 Tanzanians over the age of 65 years were found to be 14% for ε2, 61% for ε3 and 25% for ε4. By comparison, the frequency of APOE-ε4 in an age-matched demented group was also 25%. Assessment of APOE genotypes in the group of elderly Kenyan subjects from Nairobi also revealed high frequencies of the ε4 allele with no clear difference in frequency between demented and non-demented subjects. Our preliminary observations suggest that elderly East Africans with no apparent clinical AD possess relatively high APOE-ε4 allele frequencies compared to normal ageing subjects from Western countries including African-Americans. These results appear similar to those reported in a recent study in Nigerian Africans where a lack of correlation between APOE-ε4 allele frequency and Alzheimer type of dementia was noted, and imply that APOE-ε4 allele may not necessarily be a risk factor in some populations of Africa.