Carotid-artery intima and media thickness as a risk factor for myocardial infarction and stroke in older adults

Background The combined thickness of the intima and media of the carotid ar tery is associated with the prevalence of cardiovascular disease. We studie d the associations between the thickness of the carotid-artery intima and m edia and the incidence of new myocardial infarction or stroke in persons wi thout clinical cardiovascular disease. Methods Noninvasive measurements of the intima and media of the common and internal carotid artery were made with high-resolution ultrasonography in 5 858 subjects 65 years of age or older. Cardiovascular events (new myocardia l infarction or stroke) served as outcome variables in subjects without cli nical cardiovascular disease (4476 subjects) over a median follow-up period of 6.2 years. Results The incidence of cardiovascular events correlated with measurements of carotid-artery intima-media thickness. The relative risk of myocardial infarction or stroke increased with intima-media thickness (P<0.001). The r elative risk of myocardial infarction or stroke (adjusted for age and sex) for the quintile with the highest thickness as compared with the lowest qui ntile was 3.87 (95 percent confidence interval, 2.72 to 5.51). The associat ion between cardiovascular events and intima-media thickness remained signi ficant after adjustment for traditional risk factors, showing increasing ri sks for each quintile of combined intima-media thickness, from the second q uintile (relative risk, 1.54; 95 percent confidence interval, 1.04 to 2.28) , to the third (relative risk, 1.84; 95 percent confidence interval, 1.26 t o 2.67), fourth (relative risk, 2.01; 95 percent confidence interval, 1.38 to 2.91), and fifth (relative risk, 3.15; 95 percent confidence interval, 2 .19 to 4.52). The results of separate analyses of myocardial infarction and stroke paralleled those for the combined end point. Conclusions Increases in the thickness of the intima and media of the carot id artery, as measured noninvasively by ultrasonography, are directly assoc iated with an increased risk of myocardial infarction and stroke in order a dults without a history of cardiovascular disease. (N Engl J Med 1999;340:1 4-22.) (C) 1999, Massachusetts Medical Society.