Late onset Alzheimer's disease and apolipoprotein association in the Irish population: relative risk and attributable fraction

Background Familial and sporadic late onset Alzheimer's disease (LOAD) shows a consistent genetic association with APOE epsilon4. Aims To examine the role of APOE in the AD Irish population. Methods One hundred and ten Irish LOAD patients and 217 ethnically-matched controls were genotyped for APOE marker as described by Crook et al.(1) Chi square test was used to compare allelic and genotypic frequencies between patients and controls samples. Attributable fractions were calculated as described by Levin.(2) Results A highly significant association between AD and APOE epsilon4 was observed (chi(2)=37.9, p=0.0000000, RR=2.18). Further, the influence of APOEepsilon4 seems to follow a dose-dependent manner whereby individuals with the genotype APOEepsilon4/4 have a higher relative risk than those heterozygous for the epsilon4 allele (RR=4.03 and 1.76 respectively). The relative risk and the attributable fraction calculated for APOE epsilon4 are consistent with those reported for other European populations. This places the influence of this locus on AD development in the Irish population between those of the Spanish and New York white populations. Conclusion These findings provide further evidence for the importance of APOE in the development of AD.