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

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.

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.

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.

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.