The interleukin-4 -589C/T polymorphism and the risk of asthma: a meta-analysis including 7,345 cases and 7,819 controls.

A number of studies assessed the association of -589C/T polymorphism in the promoter region of interleukin-4 (IL-4) with asthma in different populations. However, the results were contradictory. A meta-analysis was conducted to investigate the association between polymorphism in the IL-4 and asthma susceptibility. Databases including Pubmed, EMBASE, Wanfang Database, China National Knowledge Infrastructure (CNKI) and Weipu Database were searched to find relevant studies. Odds ratios (ORs) with 95% confidence intervals (CIs) were used to assess the strength of associations. Thirty-four studies involving 7345 cases and 7819 controls were included. Overall, significant association between -589C/T polymorphism and asthma was observed for TT+CT vs. CC (OR=1.26; 95% CI 1.12-1.42; P=0.0001; I(2)=26%). In the subgroup analysis by ethnicity, significant associations were found among Asians (OR=1.36; 95% CI 1.07-1.73; P=0.01; I(2)=0%) and Caucasians (OR=1.30; 95% CI 1.09-1.54; P=0.004; I(2)=53%) but not among African Americans (OR=1.20; 95% CI 0.72-2.00; P=0.48; I(2)=48%). In the subgroup analysis by atopic status, no significant association was found among atopic asthma patients (OR=1.20; 95% CI 0.92-1.34; P=0.27; I(2)=6%) and non-atopic asthma patients (OR=0.97; 95% CI 0.73-1.28; P=0.81; I(2)=0%). This meta-analysis suggested that the IL-4 -589C/T polymorphism was a risk factor of asthma.