Incidence of ischemic stroke in relation to asymptomatic carotid artery atherosclerosis in subjects with normal blood pressure - A prospective cohort study

Background: Approximately 10-20% of stroke cases have normal blood pressure (BP). The objective of this study was to explore whether the risk of ischemic stroke is related to the carotid intima-media thickness (CIMT) and atherosclerotic lesions in a cohort of subjects with normal BP. Methods: Common CIMT and the presence of carotid plaque were determined by B-mode ultrasound in 6,103 subjects, randomly recruited between 1991 and 1994 from the 'Malmo Diet and Cancer' study. Normal BP was defined as BP <140/90 mm Hg, without pharmacological treatment for hypertension. Carotid artery atherosclerosis (CAA) was defined as CIMT >= 0.81 mm or/and the presence of plaque (i.e. focal CIMT >1.2 mm). The incidence of ischemic stroke was followed over a mean period of 10.7 years. Results: A total of 2,228 subjects (791 men and 1,437 women) had normal BP. During the follow-up, 34 patients suffered a first-ever ischemic stroke (crude incidence: 1.51/1,000 person-years). The Prevalences of CAA in subjects with and without stroke were 68.6 and 39.0%, respectively. It was estimated that the subjects with CAA had a 3-fold higher risk of ischemic stroke (RR: 3.33, 1.37-8.14), independent of other cardiovascular risk factors. Each increase of 1 standard deviation (0.13 mm) in CIMT increased the stroke risk by 43% (RR: 1.43, 1.002-2.02). Several factors were found to have a notable relation with CAA, including age, male sex, smoking, diabetes, systolic BP, HbA1c (glycosylated hemoglobin) and cholesterol. Conclusions: CIMT and atherosclerotic lesions are independent clinical markers for ischemic stroke among normotensive individuals. Copyright c 2008 S. Karger AG, Basel.