Lack of an association between interleukin-6 gene promoter polymorphisms (−174G/C, −572G/C) and ischemic heart disease and/or ischemic stroke: A meta-analysis

The association between single-nucleotide polymorphisms −174G/C (rs1800795) and −572G/C (rs1800796) in the interleukin-6 (IL-6) gene promoter region and ischemic heart disease (IHD)/ischemic stroke (IS) remains controversial and ambiguous. In this study, we performed a more precise estimation of the relationship by a meta-analysis based on currently available evidence from literature. To assess the effect of IL-6 polymorphisms (−174G/C, −572G/C) on IHD/IS susceptibility, a meta-analysis of 30 available studies was performed through May 2010. Summary odds ratios and their 95% confidence intervals for IL-6 polymorphisms and IHD/IS were estimated using fixed- and random-effects models when appropriate. Heterogeneity and publication bias were evaluated. When available studies were pooled into the meta-analysis, there was no significant association between IL-6 polymorphisms (−174G/C, −572G/C) and IHD/IS in any comparison model (CC vs GG, GC vs GG, dominant, and recessive models). Subgroup analyses results were consistent with the main analyses by ethnicity, ischemic types, quality score, and genotyping methods. Ethnicity (European studies) and quality score (low-quality studies) might be important sources of heterogeneity for −174G/C. However, metaregression analysis did not reveal that the foregoing characteristics could explain the τ2 in any comparison model. We could not identify the sources of heterogeneity for −572G/C. The present meta-analysis suggests that IL-6 promoter polymorphisms (−174G/C, −572G/C) were unlikely to be associated with risk of IHD and/or IS.