HbA(1c) and Coronary Heart Disease Risk Among Diabetic Patients

OBJECTIVE: Clinical trials to date have not provided definitive evidence regarding the effects of glucose lowering with coronary heart disease (CHD) risk among diabetic patients. RESEARCH DESIGN AND METHODS: We prospectively investigated the association of HbA(1c) at baseline and during follow-up with CHD risk among 17,510 African American and 12,592 white patients with type 2 diabetes. RESULTS: During a mean follow-up of 6.0 years, 7,258 incident CHD cases were identified. The multivariable-adjusted hazard ratios of CHD associated with different levels of HbA(1c) at baseline (<6.0 [reference group], 6.0–6.9, 7.0–7.9, 8.0–8.9, 9.0–9.9, 10.0–10.9, and ≥11.0%) were 1.00, 1.07 (95% CI 0.97–1.18), 1.16 (1.04–1.31), 1.15 (1.01–1.32), 1.26 (1.09–1.45), 1.27 (1.09–1.48), and 1.24 (1.10–1.40) (P trend = 0.002) for African Americans and 1.00, 1.04 (0.94–1.14), 1.15 (1.03–1.28), 1.29 (1.13–1.46), 1.41 (1.22–1.62), 1.34 (1.14–1.57), and 1.44 (1.26–1.65) (P trend <0.001) for white patients, respectively. The graded association of HbA(1c) during follow-up with CHD risk was observed among both African American and white diabetic patients (all P trend <0.001). Each one percentage increase of HbA(1c) was associated with a greater increase in CHD risk in white versus African American diabetic patients. When stratified by sex, age, smoking status, use of glucose-lowering agents, and income, this graded association of HbA(1c) with CHD was still present. CONCLUSIONS: The current study in a low-income population suggests a graded positive association between HbA(1c) at baseline and during follow-up with the risk of CHD among both African American and white diabetic patients with low socioeconomic status.