Carotid artery atherosclerosis in type-2 diabetic and nondiabetic subjects with and without symptomatic coronary artery disease (The Insulin Resistance Atherosclerosis Study)

Type-2 diabetes mellitus is associated with a 2- to 4-fold increase in the risk of clinical coronary artery disease (CAD). It has been suggested that diabetic subjects without clinical CAD should be treated as aggressively for cardiovascular risk factors as subjects with CAD. This would be warranted if diabetic subjects without clinical CAD would have accelerated CAD similar to that of nondiabetic subjects with symptomatic CAD. To assess this suggestion, we compared the intima-media wall thickness in the common carotid artery (CCA) and internal carotid artery (ICA) in 43 diabetic subjects with clinical CAD, 446 diabetic subjects without clinical CAD, 47 nondiabetic subjects with clinical CAD, and 975 nondiabetic subjects without clinical CAD (all aged 40 to 70 years) in the Insulin Resistance Atherosclerosis Study. All data were adjusted for age, gender, ethnicity, and clinical results. Both diabetes and CAD were associated with increased atherosclerosis in the CCA. Likewise, diabetes was significantly associated with increased atherosclerosis in the ICA; however, CAD was not associated with ICA intima-media wall thickness. As expected, diabetic subjects with CAD had the greatest intima-media wall thickness, whereas nondiabetic subjects without CAD had the least atherosclerosis. Subjects with diabetes but without CAD had slightly greater intima-media wall thickness than nondiabetic subjects with CAD, although these differences were not statistically significant. Thus, diabetic subjects even without CAD had extensive atherosclerosis in the carotid artery. These results support the suggestion that diabetic subjects should be treated as aggressively for cardiovascular risk factor management as subjects with pre-existing CAD.