Relationship of glycated hemoglobin A1c, coronary artery calcification and insulin resistance in males without diabetes

Background and Aims: We undertook this study to compare the prevalence of coronary artery calcification (CAC) across glycated hemoglobin A1c (HbA1c) in nondiabetic males and to evaluate the impact of insulin resistance on CAC in relation to HbA1c levels. Methods: A cross-sectional study was performed in 18,504 adult males without diabetes mellitus and cardiovascular disease (CVD). CAC scores were measured by multidetector computed tomography; CAC was defined as a CAC score >0. Insulin resistance was estimated using the homeostasis model assessment of insulin resistance (HOMA-IR). Subjects were grouped by HbA1c quartile (≤5.4%, 5.4-5.6%, 5.7%, 5.8-6.4%). Results: Thirteen percent of subjects (n=2,406) had a CAC score >0. The prevalence of CAC increased with increasing HbA1c quartile (9.4%, 11.1%, 14.1%, 17.3%). Crude odds ratios (ORs) for CAC were 1.2, 1.58 and 2.01 for the HbA1c quartiles 2, 3, and 4 when compared with the first quartile. Mean HOMA-IR levels were different among HbA1C categories and CAC status. HOMA-IR levels were higher in subjects with CAC than in those without, except in the third HbA1c quartile. Stratification by HbA1c showed a significant association between CAC and insulin resistance only in the first (OR 1.67) and fourth (OR 1.33) HbA1c quartile. After adjustment for CV risk factors, insulin resistance remained an independent predictor of CAC only in the first HbA1c quartile. Conclusions: Our study demonstrated that not only glucose status represented by HbA1c but also insulin resistance might be associated with CAC in non-diabetic Korean men. The magnitude of association of CAC with insulin resistance was greater in the lowest HbA1c quartile group.