Meta-analysis of association between ApoE epsilon 4 allele and schizophrenia

Several case-control studies have reported an association between schizophrenia and the epsilon 4 allele of Apolipoprotein E gene. The results have been equivocal. This meta-analysis has evaluated the collective evidence for an association between the e4 allele of Apolipoprotein E gene and schizophrenia. We analyzed published data sequentially first considering epsilon 4 allele itself, and then epsilon 4 carrier status as risk factors for schizophrenia using a sample of 17 population-based case-control studies, of which 6 were from Asian and 11 from Caucasian populations. The pooled odds ratios from the Caucasian populations showed a modest association with risk of schizophrenia for epsilon 4 allele and epsilon 4 carrier genotype. No other alleles or genotypes were significant in either Asian or Caucasian populations when analysed separately or combined, although the sample size had over 80% power to detect a significant odds ratio of 1.9 in Asian-population studies and 1.6 in Caucasian-population studies. After allowing for sensitivity analysis of the studies and assessment of publication bias, we conclude that the epsilon 4 allele of Apolipoprotein E does not play a major role in risk of schizophrenia in Caucasian populations. Since significant heterogeneity was present among the 6 Asian populations reported to date, further studies using larger sample sizes are required. (c) 2006 Elsevier B.V. All rights reserved.