Quantitative assessment of the effect of ABCA1 gene polymorphism on the risk of Alzheimer's disease.

ATP-binding cassette transporter A1 (ABCA1) is a membrane-associated protein which has attracted considerable attention as a candidate gene for Alzheimer's disease (AD) based on its function as a key factor in lipid metabolism by mediating cellular cholesterol efflux, the rate-limiting step in the production of nascent high-density lipoprotein (HDL) particles. The relationship between ABCA1 common variations (R219 K rs2230806, I883 M rs4149313 and R1587 K rs2230808) and AD has been reported in various ethnic groups; however, these studies have yielded contradictory results. To investigate this inconsistency, we performed a meta-analysis of 13 studies involving a total of 12,248 subjects to evaluate the effect of ABCA1 on genetic susceptibility for AD. Overall, the summary OR of AD was 1.01 (95 % CI: 0.93-1.10; P = 0.77), 1.10 (95 % CI: 0.96-1.26; P = 0.16), and 1.08 (95 % CI: 0.96-1.23; P = 0.21) for R219 K, I883 M and R1587 K polymorphism, respectively. No significant results were observed in dominant and recessive when compared with wild genotype for these polymorphisms. In the stratified analyses by ethnicity and sample size, no evidence of any gene-disease association was obtained. In conclusion, the present meta-analysis does not support the notion that common SNPs on ABCA1 is a major genetic risk factor for AD.