Delineation of prevalence and risk factors for early coronary artery disease by electron beam computed tomography in young adults with type I diabetes

OBJECTIVE - Type 1 diabetes increases the risk for coronary artery disease (CAD), but limited information is available regarding the early natural history of this process. Electron beam tomography (EBT) can measure coronary artery calcification (CAC), an early marker for CAD. This study was designed to assess the prevalence and risk factors for CAC in young adults with established type 1 diabetes. RESEARCH DESIGN AND METHODS - A total of 101 subjects aged 17-28 years with type 1 diabetes of over 5 years' duration and no history of heart disease underwent cardiac EBT with calcium scoring. Medical histories were obtained and physical examinations were conducted to document the presence of cardiac risk factors as well as evidence of microvasculopathy and diabetic arthropathy. Laboratory evaluation included measurement of fasting lipoproteins, homocysteine concentration, lipoprotein(a) [Lp(a)], urinary microalbumin, and HbA_1c. Contingency table analysis was used to assess bivariate relationships. Logistic regression was employed to construct a parsimonious model of independent risk factors. RESULTS - Eleven subjects (10.9%) had CAC. Smokers were nearly five times more likely than nonsmokers to have CAC (P = 0.03). In addition, each 0.36-mm/l increment of Lp(a) was associated with a 10% increased risk for CAC (P = 0.05) after controlling for potentially confounding factors. There was no association of other CAD or diabetes risk factors studied with CAC. CONCLUSIONS - The prevalence of early CAD as evidenced by CAC in young adults with type 1 diabetes is significant. Smoking and Lp(a) levels independently predict the presence of CAC. Additional study is necessary to delineate the natural history of CAC and the role of risk factor modification to prevent progression of CAD in this high-risk population.