Association Between the Interleukin-4 Gene C-589T and C+33T Polymorphisms and Asthma Risk: A Meta-analysis

Abstract

A large number of studies have investigated the correlation between the interleukin (IL)-4 C-589T and C+33T polymorphisms and asthma susceptibility. However, the results are inconsistent. The objective of this study is to explore the association between the IL-4 C-589T and C+33T polymorphisms and asthma risk using meta-analysis. A total of 35 studies (31 concerning C-589T polymorphism and asthma risk with 4737 asthmatics and 6389 controls and 14 studies regarding C+33T polymorphism and asthma risk with 2544 asthmatics and 4049 controls) were included in this meta-analysis. The IL-4 C-589T polymorphism was associated with increased asthma risk in a dominant genetic model (odds ratio [OR] [95% confidence interval (CI)] = 1.284 [1.131-1.459] for TT + TC vs. CC). In the subgroup analyses by ethnicity, age and atopic status of asthmatics, significantly increased risks of asthma were found both in Asians (OR [95% CI] = 1.301 [1.003-1.689]) and Caucasians (OR [95% CI] = 1.314 [1.061-1.628]) and in both adults (OR [95% CI] = 1.299 [1.098-1.537]) and children (OR [95% CI] = 1.464 [1.044-2.052]). As for the C+33T polymorphism, the results showed that it was correlated with elevated asthma risk in a recessive genetic model (OR [95% CI] = 1.744 [1.215-2.504] for TT vs. CT + CC). After stratifying analyses by ethnicity, age and atopic status of asthmatics, significantly increased asthma risks were observed in Asians (OR [95% CI] = 1.223 [1.037-1.442]), Caucasians (OR [95% CI] = 3.036 [1.224-7.529]), and children (OR [95% CI] = 1.300 [1.075-1.573]) in a recessive genetic model. This meta-analysis suggests that the IL-4 C-589T and C+33T polymorphisms may be risk factors for asthma.