Carotid plaque area and intima-media thickness in prediction of first-ever ischemic stroke: a 10-year follow-up of 6584 men and women: the Tromsø Study.

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.