Relationship of Hemoglobin A1C and Mortality in Heart Failure Patients With Diabetes

Objectives: This study was designed to examine the relationship between glycosylated hemoglobin (HbA1C) and adverse outcomes in diabetic patients with established heart failure (HF). Background: Despite the common coexistence of diabetes and HF, previous studies examining the association between HbA1C and outcomes in this population have been limited and have reported discrepant results. Methods: We assessed the association between increasing quintiles (Q1 to Q5) of HbA1C and risk of death or risk of HF hospitalization by conducting a retrospective study in a national cohort of 5,815 veterans with HF and diabetes treated in ambulatory clinics at Veterans Affairs medical centers. Results: At 2 years of follow-up, death occurred in 25% of patients in Q1 (HbA1C ≤6.4%), 23% in Q2 (6.4% < HbA1c ≤7.1%), 17.7% in Q3 (7.1% < HbA1c ≤7.8%), 22.5% in Q4 (7.8% < HbA1c ≤9.0%), and 23.2% in Q5 (HbA1c >9.0%). After adjustment for potential confounders, the middle quintile (Q3) had reduced mortality when compared with the lowest quintile (risk-adjusted hazard ratio: 0.73, 95% confidence interval: 0.61 to 0.88, p = 0.001). Hospitalization rates for HF at 2 years increased with increasing quintiles of HbA1C (Q1: 13.3%, Q2: 13.1%, Q3: 15.5%, Q4: 16.4%, and Q5: 18.2%), but this association was not statistically significant when adjusted for potential confounders. Conclusions: The association between mortality and HbA1C in diabetic patients with HF appears U-shaped, with the lowest risk of death in those patients with modest glucose control (7.1% < HbA1C ≤7.8%). Future prospective studies are necessary to define optimal treatment goals in these patients.