Coronary Artery Calcification in Type 2 Diabetes and Insulin Resistance

Abstract

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.