IL-6 gene polymorphisms and CAD risk: a meta-analysis.

The potential relationship between Interleukin-6 (IL-6) gene polymorphisms and coronary artery disease (CAD) has been widely investigated. However, study findings on the -174 G/C and -572 G/C variants remain inconsistent and somewhat controversial. The present meta-analysis was conducted in an attempt to provide a more robust synthesis conclusion. PubMed and Embase were used to search for all relevant studies published on or before May 22, 2012. A total of 19 studies were ultimately included in the analysis. Overall combined risk was calculated with fixed or random-effects models. Subgroup and sensitivity analyses were performed. Among the included studies, no statistically significant differences were found between controls and CAD cases for the G allele contrasts of the -174 G/C and -572 G/C polymorphisms. The co-dominant genetic model was evaluated for the -174 G/C polymorphism. A significant association was detected using GG versus CC (OR = 0.801, 95 % CI: [0.652, 0.983], P = 0.034). However, the association was not obviously in subgroup analysis by ethnicity. The recessive genetic model was evaluated for the -572 G/C polymorphism. The relationship between -572 G/C polymorphism and CAD risk was only found to be significant in Asian populations (random-effects: OR = 1.908, 95 % CI: [1.016, 3.581], P = 0.044) using GG versus GC+CC. No obvious publication bias was found by Begg's funnel plots and the Egger's linear regression test (P = 0.315 for -174 G/C polymorphism and P = 0.118 for -572 G/C polymorphism). Our study indicated that the association between the IL-6 gene and CAD risk was mild and moderate for the -174 G/C and -572 G/C polymorphisms. However, this relationship requires additional investigation through well-designed studies with larger sample sizes.