Common Carotid Intima-Media Thickness and Framingham Risk Score Predict Incident Carotid Atherosclerotic Plaque Formation

Abstract

Cross-sectional studies describe a positive association between common carotid artery intima-media thickness (CCA-IMT) and carotid plaques (CP). However, longitudinal data on the predictive value of CCA-IMT for occurrence of CP are limited. Therefore, the role of increasing CCA-IMT in the atherosclerotic process is still discussed controversially. We investigated the predictive value of CCA-IMT and the Framingham risk score (FRS) for incident CP formation in a population-based longitudinal study of 1922 subjects aged 45 to 81 years who underwent ultrasonography of both carotid arteries and received vascular risk factor assessment at baseline and after 5 years. CP was defined as any protruding focal thickening of the intima-media complex. Incident CP formation during follow-up was defined as the appearance of at least 1 CP in a previously plaque-free arterial segment (right and left common, internal, and external carotid arteries and carotid bifurcation). Among the 636 subjects without CP at baseline, 418 (66%) had at least 1 incident CP during follow-up. In a multivariable negative binominal regression model adjusted for age, gender, and the FRS, the number of arterial segments affected by incident CP was 1.53-fold higher (CI, 1.12-2.07; P<0.01) for subjects in the highest quartile of the overall CCA-IMT distribution compared to those in the lowest quartile. Both CCA-IMT and FRS independently predict incident CP formation. The risk of CP formation may actually be underestimated in subjects with low FRS and high IMT.