HbA1c 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.