Background and purpose: Carotid plaque and intima-media thickness (IMT) are recognized as risk factors for ischemic stroke, but their predictive value has been debated and varies between studies. The purpose of this longitudinal population-based study was to assess the risk of ischemic stroke associated with plaque area and IMT in the carotid artery.
Methods: IMT and total plaque area in the right carotid artery were measured with ultrasound in 3240 men and 3344 women aged 25 to 84 years who participated in a population health study in 1994 to 1995. First-ever ischemic strokes were identified through linkage to hospital and national diagnosis registries, with follow-up until December 31, 2005.
Results: Incident ischemic strokes occurred in 7.3% (n=235) of men and 4.8% (n=162) of women. The hazard ratio for 1 SD increase in square-root-transformed plaque area was 1.23 (95% CI, 1.09-1.38; P=0.0009) in men and 1.19 (95% CI, 1.01-1.41; P=0.04) in women when adjusted for other cardiovascular risk factors. The multivariable-adjusted hazard ratio in the highest quartile of plaque area versus no plaque was 1.73 (95% CI, 1.19-2.52; P=0.004) in men and 1.62 (95% CI, 1.04-2.53; P=0.03) in women. The multivariable-adjusted hazard ratio for 1 SD increase in IMT was 1.08 (95% CI, 0.95-1.22; P=0.2) in men and 1.24 (95% CI, 1.05-1.48; P=0.01) in women. There were no differences in stroke risk across quartiles of IMT in multivariable analysis.
Conclusions: In the present study, total plaque area appears to be a stronger predictor than IMT for first-ever ischemic stroke.