Association of HbA1c With Hospitalization Among Patients With Heart Failure and Diabetes

Abstract

Background: Comorbid diabetes is common in heart failure and associated with increased hospitalization and mortality. Nonetheless, the optimal treatment strategy for diabetes in heart failure patients remains poorly characterized, particularly among low income and minority populations. The purpose of this study was to evaluate the association between glycemic control and outcomes among patients with heart failure and diabetes who were seen in a safety net health care system. Methods: We performed a retrospective cohort study of outpatients with heart failure and diabetes in the New York City Health and Hospitals Corporation, the largest municipal health care system in the United States. Subjects with diagnoses of heart failure and diabetes mellitus were included if they had an outpatient visit in 2007-2010 with an HbA1c performed in the prior 90 days. HbA1c and covariates, including demographics, comorbidities, vital signs, labs, and prior utilization, were obtained from the HHC data warehouse, which was linked to the New York State Inpatient Database and to New York State Vital Statistics to ascertain hospitalization and mortality events, respectively. Cox proportional hazard models were used to measure the association between HbA1c levels and outcomes of all-cause hospitalization, heart failure hospitalization, and mortality. Results: Of 4,723 patients with heart failure and diabetes, 42.6% were black, 30.5% were Hispanic/ Latino, 31.4% were Medicaid beneficiaries and 22.9% were uninsured. As compared to patients with an HbA1c of 8.0-8.9%, patients with an HbA1c of !6.5%, 6.5-6.9%, 7.0-7.9%, and $9.0% had an adjusted hazard ratio (aHR) (95% CI) for all-cause hospitalization of 1.03 (0.90-1.17), 1.05 (0.91-1.22), 1.03 (0.90-1.17), and 1.13 (1.00-1.28), respectively. An HbA1c$9.0% was also associated with an increased risk of heart failure hospitalization (aHR 1.33; 95% CI 1.111.59) and a non-significant increased risk in mortality (aHR 1.20; 95% CI 0.99-1.45) when compared to HbA1c of 8.0-8.9%. Conclusions: Among a cohort of primarily minority and low income patients with heart failure and diabetes, an increased risk of hospitalization was observed only for an HbA1c greater than 9%.