Carotid wall thickness is predictive of incident clinical stroke - The Atherosclerosis Risk in Communities (ARIC) Study

Few studies have determined whether carotid artery intima-media thickness ( IMT) is associated prospectively with risk of first ischemic stroke. In the Atherosclerosis Risk in Communities Study, carotid IMT, an index of genera lized atherosclerosis, was defined as the mean of IMT measured by B-mode ul trasonography at six sites of the carotid arteries. The authors assessed th e relation of mean IMT to stroke incidence over 6-9 years' followup (1987-1 995) among 7,865 women and 6,349 men aged 45-64 years without prior stroke at baseline in four US communities. There were 90 incident ischemic stroke events for women and 109 for men. In sex-specific Cox proportional hazards models adjusting only for age, race, and community, the hazard rate ratios comparing extreme mean IMT values (greater than or equal to 1 mm) to values less than 0.6 mm were 8.5 for women (95% confidence interval: 3.5, 20.7) a nd 3.6 for men (95% confidence interval: 1.5, 9.2). The relation was graded , and models with cubic splines indicated significant nonlinearity, with ha zards increasing more rapidly at lower IMTs than at higher IMTs. Thus, mode ls using linear IMT values substantially underestimate the strength of the association at lower IMTs, The strength of the association was reduced by t he inclusion of putative stroke risk factors, but it remained elevated at h igher IMTs. Hence, mean carotid IMT is a noninvasive predictor of future is chemic stroke incidence.