Association of interleukin-13 C-1112T and G+2044A polymorphisms with asthma: A meta-analysis

Background and objective: Polymorphisms in the IL13 gene have been reported to be associated with susceptibility to asthma. However, a number of studies have shown inconsistent results. A meta-analysis was performed to investigate whether polymorphisms in the IL13 gene were associated with the risk of asthma. Methods: Searches were performed of the Medline and Chinese National Knowledge Infrastructure (CNKI) databases, covering all papers published up to 31 August 2010. A recently proposed logistic regression-based method for meta-analysis of case-control genetic association studies was used to analyse pooled data. All statistical analyses were performed using STATA version 10.0 software. Results: The IL13 C-1112T and G+2044A polymorphisms were investigated in 10 and 14 studies, respectively. The summary estimates suggested that both these polymorphisms were associated with susceptibility to asthma. Carriers of the IL13 -1112T allele had a 38.9% increased risk of asthma compared with homozygotes (-1112CC) (odds ratio (OR) 1.389, 95% confidence interval (CI): 1.103-1.749). Carriers of the IL13 +2044A allele had a 40.0% increased risk of asthma compared with homozygotes (+2044GG) (OR 1.400, 95% CI: 1.137-1.724). In a subgroup analysis by ethnicity, the IL13 -1112T allele was associated with an increased risk of asthma among Caucasians (OR 1.629, 95% CI: 1.255-2.113) but not among Asians, and the IL13 +2044A allele was associated with an increased risk of asthma among Asians (OR 1.436, 95% CI: 1.101-1.873) but not among Caucasians. Conclusions: This meta-analysis indicated that the IL13 C-1112T and G+2044A polymorphisms predispose to asthma. Further studies, including pooling of individual data to facilitate evaluation of gene-gene and gene-environment interactions between these IL13 gene polymorphisms and asthma susceptibility, are recommended.