Associations of risk factors with segment-specific intimal-medial thickness of the extracranial carotid artery

Background and Purpose-It is generally assumed that risk factors affect ext racranial carotid intimal-medial thickness similarly among all arterial seg ments. This assumption underlies use of single segments or walls of segment s as outcome variables for risk factor studies and clinical trials. However , if the impact of risk factors was unequal for various segments or circumf erentially asymmetrical within segments, then inferences drawn from a singl e segment or wall might not be generalizable; furthermore, since individual segments and walls have unique histological characteristics and are differ entially exposed to turbulent flow, risk factor relationships with a partic ular segment or wall may provide inferences regarding pathogenesis of ather osclerosis. Methods-We evaluated associations of risk factors with intimal-medial thick ness at the near and far walls of the common carotid artery, bifurcation, a nd internal carotid artery in 280 individuals older than 45 years equally d ivided between coronary artery disease cases and controls and between men a nd women. Results-The patterns of differences in mean intimal-medial thickness among segments vary, depending on age, history of hypertension, body mass index i n women, and coronary (case-control) status. The asymmetry of disease depen ded on blood glucose concentrations, prior history of diabetes, smoking, an d coronary status. Sex, postmenopausal status, LDL cholesterol, systolic bl ood pressure, and history of myocardial infarction all had statistically si gnificant relationships with intimal-medial thickness that were fairly homo geneous among arterial sites. Conclusions-Focus on an individual segments or walls of the extracranial ca rotid arteries may lead to overestimation or underestimation of association s of risk factors with extracranial carotid intimal-medial thickness.