Interleukin-6 gene -174G/C polymorphism and bronchial asthma risk: a meta-analysis

The Interleukin-6 (IL-6) genetic polymorphism is associated with bronchial asthma, a number of studies have been conducted to investigate the association between IL-6 gene -174G/C polymorphism and bronchial asthma risk. However, the results are inconclusive. This meta-analysis aims to investigate whether -174G/C polymorphism is a potential risk factor for bronchial asthma. We searched Web of Science, PubMed, Google Scholar, China National Knowledge Infrastructure (CNKI) and Wanfang Database from inception through December 1st, 2014. Meta-analysis was performed using the STATA 12.0. Overall, a significantly reduced risk for asthma was found in IL-6 -174 CC genotype (CC vs. GG: OR = 0. 51, 95% CI = 0.27-0.96, P = 0.038). Furthermore, analysis by ethnicity indicated that there was a markedly reduced risk for asthma in IL-6 -174 CC genotype in Caucasian (CC vs. GG: OR = 0.51, 95% CI = 0.27-0.96, P = 0.038). Analysis by age indicated that there was a significantly reduced risk for asthma in IL-6 -174 CC genotype in adults (CC vs. GG: OR = 0.47, 95% CI = 0.23-0.97, P = 0.042). In conclusion, the current meta-analysis indicates that IL-6 -174 CC genotype may be a protective factor against asthma in Caucasian and adults.