Background and purpose: Carotid intima-media thickness (IMT) is an independent predictor of vascular events in age groups >45 years. However, there is little information about the predictive value of IMT in younger individuals.
Methods: In the Carotid Atherosclerosis Progression Study (CAPS; n=5056; age range 19 to 90 years; mean age 50.1 years), common carotid artery (CCA) IMT, bifurcation IMT, internal carotid artery IMT and vascular risk factors were evaluated at baseline. The incidence of stroke, myocardial infarction (MI), and death was determined prospectively. Data for younger (<50 years; n=2436) and older subjects (> or =50 years; n=2620) were analyzed separately using Cox proportional hazard regression models.
Results: During a mean follow-up period of 4.2 years, there were 228 cases of MI, 107 strokes, and 50 deaths. IMT at all carotid segments was highly predictive of all end points (eg, hazard rate ratios [HRRs] per 1 SD CCA-IMT increase were 1.43 [95% CI: 1.35 to 1.51] for MI, 1.47 [1.35 to 1.60] for stroke, and 1.45 [1.38 to 1.52] for MI, stroke or death; all P<0.0001). Even after adjustment for age, sex, and vascular risk factors, the predictive value of CCA-IMT and bifurcation IMT remained significant for MI and the combined end point. For the latter, the HRRs were considerably higher in the younger than in the older age group (eg, HRR per 0.1 mm CCA-IMT was 1.34 [1.16 to 1.55] vis-à-vis 1.10 [1.05 to 1.15]; P=0.011 for age-IMT interaction).
Conclusions: Carotid IMT independently predicts future vascular events. Its predictive value is at least as high in younger subjects as in older subjects.