Background: Interleukin 6 trans-signalling is independently associated with the risk of cardiovascular events. The aim of this study was to investigate if interleukin 6 trans-signalling can identify individuals at risk for cardiovascular events (coronary artery disease and ischaemic stroke) among those at-low-intermediate risk.
Methods: In a cohort of 60-year-olds (n = 4232, incident cardiovascular events n = 525), interleukin 6 trans-signalling was estimated by a ratio between the pro-inflammatory interleukin 6: soluble interleukin 6 receptor binary receptor complex and the inactivated interleukin 6: soluble interleukin 6 receptor: sgp130 ternary complex (B/T ratio). Risk associated with B/T ratio >median was investigated in individuals with low-density lipoprotein cholesterol ≤4.0 (mmol/l) and in those at low-intermediate risk according to the Framingham risk score (FRS) using Cox regression and expressed as hazard ratio and 95% confidence interval. Difference in time to event (years; 95% confidence interval) was analysed with quantile regression. The interaction between low-density lipoprotein cholesterol and B/T ratio was estimated on the additive scale. Incremental discriminatory value of the B/T ratio if low-density lipoprotein cholesterol ≤4.0 was compared to that of the FRS and interleukin 6.
Results: B/T ratio >median was associated with increased cardiovascular event risk when low-density lipoprotein cholesterol ≤4.0 (hazard ratio 1.59; 95% confidence interval 1.24-2.05) or FRS ≤ 10%, >10-≤20% (hazard ratio 1.27; 95% confidence interval 1.00-1.61 and hazard ratio 1.78; 95% confidence interval 1.36-2.34, respectively). B/T ratio >median and low-density lipoprotein cholesterol ≤4.0 were associated with early cardiovascular events, particularly ischaemic stroke. No interaction was observed between low-density lipoprotein cholesterol and the B/T ratio, both factors increasing cardiovascular event risk by 60%. In the presence of low-density lipoprotein cholesterol ≤4.0, the B/T ratio slightly improved discrimination measures.
Conclusions: Interleukin 6 trans-signalling increases cardiovascular event risk in middle-aged men and women otherwise classified at low-intermediate cardiovascular risk.
Keywords: Biomarker; cardiovascular disease; cerebrovascular disease/stroke; coronary artery disease; inflammation.