Monocyte count, but not C-reactive protein or interleukin-6, is an independent risk marker for subclinical carotid atherosclerosis

Abstract

Background and Purpose-Systemic inflammatory markers have been shown to predict future cardiovascular events, but whether they are associated with early atherosclerosis is uncertain. We investigated the relationship of inflammatory markers interleukin-6 (IL-6), high-sensitive C-reactive protein (hs-CRP), fibrinogen, monocyte count, and white cell count (WCC) with subclinical carotid atherosclerosis in a healthy community population. Methods-B-mode carotid ultrasound was performed on 1111 randomly selected male and female subjects aged 27 to 77 years. Serum IL-6, hs-CRP, plasma fibrinogen, monocyte count, and WCC were measured on all subjects, along with conventional cardiovascular risk factors. Results-Multivariate analysis showed that IL-6 (P<0.0001), fibrinogen (P=0.007), and monocyte count (P=0.001) were associated with carotid plaque formation in the whole population. Monocyte count remained associated independently with carotid plaque formation when adjusted further for conventional risk factors (odds ratio per SD increase in monocyte count 1.4; 95% CI, 1.13 to 1.73; P=0.002). IL-6 (P<0.0001), fibrinogen (P<0.0001), and monocyte count (P=0.04) were also associated with carotid intima-medial thickness (IMT) in the whole population. However, when adjusted further for conventional risk factors, none remained independently predictive of carotid IMT. Further analysis showed an age-monocyte interaction (P=0.03), with monocyte count being an independent predictor of carotid IMT in the older age group only (>53 years; P=0.003). Conclusion-In a healthy community population, monocyte count is a better independent predictor of common carotid IMT and plaque formation than IL-6, hs-CRP, fibrinogen, and WCC. Monocyte count may represent an inexpensive, easy-to-measure risk marker for subclinical carotid atherosclerosis.