Effects of polymorphisms -1112C/T and +2044A/G in interleukin-13 gene on asthma risk: a meta-analysis.

Background: Associations between interleukin-13 (IL-13) polymorphisms and asthma risk remained controversial and ambiguous. Therefore, we performed a meta-analysis to assess the associations between IL-13 polymorphisms and asthma susceptibility.
Methods: Pubmed, EMBASE, Chinese National Knowledge Infrastructure (CNKI) and Wangfang databases were searched. Odds ratios (ORs) with 95% confidence intervals (CIs) were used to calculate the strength of association in the random-effects model.
Results: Thirty-four studies were included in this meta-analysis. The results indicated that IL13 -1112C/T polymorphism was significantly associated with asthma risk (OR=1.20, 95% CI 1.08-1.34, P=0.0009) in a dominant genetic model. When stratifying for race, IL13 -1112C/T polymorphism exhibited increased asthma risk in Caucasians (OR=1.30, 95% CI 1.09-1.55, P=0.003), while no significant association was found in Asians and African Americans. In the subgroup analysis based on atopic status, significant association was observed in atopic patients (OR=1.25, 95% CI 1.07-1.45, P=0.004) but not in the non-atopic patients. In addition, a significant association between IL13+2044A/G polymorphism and asthma risk was observed (OR=1.18, 95% CI 1.08-1.28, P=0.0002). In the subgroup analysis by ethnicity, there were significant associations between IL13+2044A/G polymorphism and asthma risk in Asians (OR=1.19, 95% CI 1.04-1.36, P=0.01) and Caucasians (OR=1.22, 95% CI 1.06-1.40, P=0.005) but not in African Americans. In the subgroup analysis stratified by atopic status, a marginal significant association was found in atopic patients (OR=1.12, 95% CI 1.00-1.26, P=0.05).
Conclusions: This meta-analysis suggested that the IL13 -1112C/T and +2044A/G polymorphisms were risk factors for asthma.