Frequency distribution of apolipoprotein E genotypes in elderly population and relationship with senile dementia

The aim of this study was to determine the relationship between apolipoprotein E (ApoE)-ε4 genotype and senile dementia (SD) by analyzing the ApoE allelic frequency distributions among the elderly Han Chinese population.

For this purpose, a total of 316 Chongqing residents aged ≥60 years were classified as SD or control groups following the criteria of National Institute of Neurological and Communicative Disorders and Stroke-Alzheimer's Disease and Related Disorders Association. Genomic DNA was isolated from the peripheral blood lymphocytes and exon 4 of the ApoE gene with polymorphism sites was amplified by PCR and genotypes determined by restriction fragment length polymorphism (RFLP).

We found that the most prevalent genotype was ApoE-ε3/3, followed in order by ApoE-ε3/4 and ApoE-ε2/2. The estimated ApoE allelic frequencies in individuals with SD were 0.095, 0.560, and 0.345 for ε2, ε3, and ε4, respectively. In controls, the corresponding ApoE allelic frequencies were 0.146, 0.699, and 0.155. The percentage of ε4 allele carriers in SD group was significantly higher than that in control group (P<0.01); while those of ε2 and ε3 genotypes were lower in SD group as compared with control group.

We concluded that in the elderly Han Chinese residents of Chongqing aged 60 years and over, ApoE-ε3/3 and ApoE-ε2/2 were the most and least prevalent genotypes, respectively. Further, based on strong linkage, ApoEε4 allele might be a significant risk factor for the development of senile dementia.