Coronary Artery Calcification in Type 2 Diabetes and Insulin Resistance

OBJECTIVE: To assess risk for subclinical coronary atherosclerosis using electron beam- computed tomography in subjects with or without insulin resistance and with normal glucose tolerance (NGT) or impaired glucose tolerance (IGT/impaired fasting glucose [IFG]) or type 2 diabetes. RESEARCH DESIGN AND METHODS: We categorized glucose tolerance by type 2 diabetes therapy (diagnosed diabetes) or with an oral glucose tolerance test (OGTT) (IFG, IGT, and OGTT-detected diabetes) and insulin resistance as an elevated fasting insulin level, in subjects attending the fifth examination (1991-1995) of the Framingham Offspring Study. A representative subset of subjects without clinical atherosclerosis was selected for electron beam computed tomography in 1998-1999 from age- and sex-stratified quintiles of the Framingham risk score. The presence of subclinical atherosclerosis was defined as the upper quartile of the Agatston score distribution (score > 170). We assessed risk for subclinical atherosclerosis using multivariable logistic regression. RESULTS: Of 325 subjects aged 31-73 years, 51% were men, 11.2% had IFG/IGT, and 9.9% had diabetes (2.8% with diagnosed diabetes); 14.5% had insulin resistance. Compared with NGT, subjects with IFG/IGT tended to be more likely (adjusted odds ratio 1.5, 95% CI 0.7-3.4) and those with diabetes were significantly more likely (2.7, 1.2-6.1) to have subclinical coronary atherosclerosis. In age- and sex-adjusted models, subjects with insulin resistance were more likely to have subclinical atherosclerosis than those without insulin resistance (2.1, 1.01-4.2), but further risk factor adjustment weakened this association. In adjusted models including insulin resistance, diabetes remained associated with risk for subclinical atherosclerosis (2.8, 1.2-6.7); diagnosed diabetes (6.0, 1.4-25.2) had a larger effect than OGTT-detected diabetes (2.1, 0.8-5.5). CONCLUSIONS: Individuals with diabetes have an elevated burden of subclinical coronary atherosclerosis. Aggressive clinical atherosclerosis prevention is warranted, especially in diagnosed diabetes.