Clinical Outcomes With Metformin and Sulfonylurea Therapies Among Patients With Heart Failure and Diabetes

Abstract

Objectives: The authors sought to characterize associations between initiation of metformin and sulfonylurea therapy and clinical outcomes among patients with comorbid heart failure (HF) and diabetes (overall and by ejection fraction [EF] phenotype).

Background: Metformin and sulfonylureas are frequently prescribed to patients with diabetes for glycemic control. The impact of these therapies on clinical outcomes among patients with comorbid HF and diabetes is unclear.

Methods: The authors evaluated Medicare beneficiaries hospitalized for HF in the Get With The Guidelines-Heart Failure Registry between 2006 and 2014 with diabetes and not prescribed metformin or sulfonylurea before admission. In parallel separate analyses for metformin and sulfonylurea, patients with newly prescribed therapy within 90 days of discharge were compared with patients not prescribed therapy. Multivariable models landmarked at 90 days evaluated associations between prescription of therapy, and mortality and hospitalization for HF (HHF) at 12 months. Negative control (falsification) endpoints included hospitalization for urinary tract infection, hospitalization for gastrointestinal bleed, and influenza vaccination. Prespecified subgroup analyses were stratified by EF ≤40% versus >40%.

Results: Of 5,852 patients, 454 (7.8%) were newly prescribed metformin and 504 (8.6%) were newly prescribed sulfonylurea. After adjustment, metformin prescription was independently associated with reduced risk of composite mortality/HHF (HR: 0.81; 95% CI: 0.67-0.98; P = 0.03), but individual components were not statistically significant. Findings among patients with EF >40% accounted for associations with mortality/HHF (HR: 0.68; 95% CI: 0.52-0.90) and HHF (HR: 0.58; 95% CI: 0.40-0.85) endpoints (all P for interaction ≤0.04). After adjustment, sulfonylurea initiation was associated with increased risk of mortality (HR: 1.24; 95% CI: 1.00-1.52; P = 0.045) and HHF (HR: 1.22; 95% CI: 1.00-1.48; P = 0.050) with nominal statistical significance. Associations between sulfonylurea initiation and endpoints were consistent regardless of EF (all P for interaction >0.11). Neither metformin initiation nor sulfonylurea initiation were associated with negative control endpoints.

Conclusions: In this population of older U.S. adults hospitalized for HF with comorbid diabetes, metformin initiation was independently associated with substantial improvements in 12-month clinical outcomes, driven by findings among patients with EF >40%. By contrast, sulfonylurea initiation was associated with excess risk of death and HF hospitalization, regardless of EF.

Keywords: diabetes; ejection fraction; heart failure; metformin; sulfonylurea.