Correlative association of interleukin-6 with intima media thickness: a meta-analysis.

Background: Involvement of inflammatory processes in the atherogenesis is now well-recognized. The present study examines the relationship between a proinflammatory cytokine, interleukin-6 (IL-6), and atherosclerosis by meta-analyzing the correlation coefficients between IL-6 and intima media thickness reported in the relevant studies.

Method: Relevant research articles were searched in several electronic databases by using most relevant MeSH terms and keywords. For the meta-analyses, correlation coefficients of individual studies were first converted into Fisher's z scores and then overall effect size was transformed into correlation coefficient. Between-study hete rogeneity was tested by I(2) index and subgroup analyses were performed. Quality of the included studies was assessed and tests for publication bias were carried out.

Results: Thirty seven studies were selected for the meta-analysis from which data of 14832 participants including healthy persons, persons at risk of CVD and patients of various diseases is used. The effect size (correlation coefficient) with 95% confidence interval (CI) between IL-6 and intima media thickness was 0.336 (0.327 to 0.345); P < 0.0001 in the overall meta-analysis, 0.446 (0.422 to 0.47); P < 0.0001 in patients suffering from any pathological condition; 0.478 (0.446 to 0.508); P < 0.0001 in patients suffering either from a CVD or a disease which poses risk of CVD; 0.327 (0.264 to 0.388); P < 0.0001 in patients suffering from a disease with no CVD risk; and 0.31 (0.291 to 0.327); P < 0.0001 in participants of community-based surveys. There was no significant publication bias.

Conclusion: Intima media thickness is significantly correlated with IL-6 levels in the patients with CVD or a disease posing risk of CVD as well as in apparently healthy populations.