Carotid artery wall thickness and risk of stroke subtypes: The atherosclerosis risk in communities study

Background and Purpose- Understanding associations of carotid atherosclerosis with stroke subtypes may contribute to more effective prevention of stroke. Methods- Between 1987 and 1989, 13 560 men and women aged 45 to 64 years and free of clinical stroke took part in the first examination of the Atherosclerosis Risk in Communities (ARIC) study. Incident strokes were ascertained by hospital surveillance. Results- During an average follow-up of 15.7 years, 82 incident hemorrhagic and 621 incident ischemic strokes (131 lacunar, 358 nonlacunar, and 132 cardioembolic strokes) occurred. The incidence rates of hemorrhagic and ischemic strokes were greater across higher carotid intima-media thickness levels. Although this positive association was observed for all stroke subtypes, the age-, gender-, and race-adjusted risk ratios were higher for cardioembolic and nonlacunar strokes than for hemorrhagic and lacunar strokes. Compared with participants in the lowest quintile (<0.61 mm), the adjusted risk ratios for those in the highest quintile (0.85 mm) of intima-media thickness were 2.55 (95% CI, 1.09-5.94) for hemorrhagic, 2.89 (95% CI, 1.50-5.54) for lacunar, 3.61 (95% CI, 2.33-5.99) for nonlacunar, and 6.12 (95% CI, 2.71-13.9) for cardioembolic stroke. The risk ratios were attenuated by additional adjustment for covariates but remained statistically significant for nonlacunar and cardioembolic strokes (P for trend <0.001, respectively). The association between carotid intima-media thickness and lacunar stroke was somewhat stronger in blacks than in whites (P for interaction=0.07). Conclusions- Carotid atherosclerosis was associated with increased risk of all stroke subtypes, but the association of carotid atherosclerosis with stroke may vary by subtypes.