Association of interleukin-6 with the progression of carotid atherosclerosis: a 9-year follow-up study

Background and purpose: Limited information is available on the long-term effects of interleukin-6 (IL-6) on systemic atherosclerosis. The purpose of the present study was to clarify the relationship between chronic elevation of IL-6 and the long-term progression of carotid atherosclerosis.

Methods: We prospectively evaluated 210 patients with ≥1 vascular risk factors for 9.0±1.0 years. Carotid mean-maximal intima-media thickness (mmIMT), the serum high-sensitivity C-reactive protein (hs-CRP) level, and the serum IL-6 level were measured at baseline and every 3 years. The associations between the progression of mmIMT and the long-term average levels of hs-CRP and IL-6 were analyzed.

Results: Carotid mmIMT increased throughout the study period (0.031±0.026 mm/y). Baseline mmIMT was significantly associated with baseline hs-CRP (P=0.002) and baseline IL-6 (P<0.001) levels. Progression of mmIMT was positively correlated with average hs-CRP (P=0.001) and average IL-6 (P<0.001) levels. When adjusted for age, sex, traditional risk factors, and baseline mmIMT, mmIMT progression remained significantly associated only with the average IL-6 level (standardized β=0.17; P=0.02), but not with the average hs-CRP level (standardized β=0.10; P=0.18).

Conclusions: Chronic elevation of serum IL-6 was associated with the progression of atherosclerosis in patients with vascular risk factors. IL-6 could be used as a quantitative marker and a potential therapeutic target for accelerated atherosclerosis.