Apolipoprotein E gene polymorphism and the risk of intracerebral hemorrhage: a meta-analysis of epidemiologic studies

Background: Studies investigating the association between the apolipoprotein E (APOE) gene polymorphism and the risk of intracerebral hemorrhage (ICH) have reported conflicting results. We here performed a meta-analysis based on the evidence currently available from the literature to make a more precise estimation of this relationship. Methods: Published literature from the National Library of Medline and Embase databases were retrieved. Odds ratio (OR) and 95% confidence interval (CI) were calculated in fixed-or random-effects models when appropriate. Subgroup analyses were performed by race. Results: This meta-analysis included 11 case-control studies, which included 1,238 ICH cases and 3,575 controls. The combined results based on all studies showed that ICH cases had a significantly higher frequency of APOE epsilon 4 allele (OR=1.42, 95% CI=1.21,1.67, P<0.001). In the subgroup analysis by race, we also found that ICH cases had a significantly higher frequency of APOE epsilon 4 allele in Asians (OR=1.52, 95% CI=1.20,1.93, P<0.001) and in Caucasians (OR=1.34, 95% CI=1.07,1.66, P=0.009). There was no significant relationship between APOE epsilon 2 allele and the risk of ICH. Conclusion: Our meta-analysis suggested that APOE epsilon 4 allele was associated with a higher risk of ICH.