The interleukin-4-589C/T polymorphism and the risk of asthma: A meta-analysis including 7345 cases and 7819 controls

Background: 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. Methods: 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. Results: 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 = 136; 95% CI 1.07-1.73; P = 0.01; I-2 = 0%) and Caucasians (OR = 130; 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 = 027; I-2 = 6%) and non-atopic asthma patients (OR = 0.97; 95% CI 0.73-1.28; P = 0.81; I-2 = 0%). Conclusions: This meta-analysis suggested that the IL-4 -589C/T polymorphism was a risk factor of asthma. (C) 2013 Published by Elsevier B.V.