Risk of overall mortality and cardiovascular events in patients with type 2 diabetes on dual drug therapy including metformin: A large database study from the Cleveland Clinic.

Background: The aim of the present study was to assess the risk of overall mortality, coronary artery disease (CAD), and congestive heart failure (CHF) in patients with type 2 diabetes mellitus (T2DM) treated with metformin (MF) and an additional antidiabetic agent.
Methods: A retrospective cohort study was conducted using an academic health center enterprise-wide electronic health record (EHR) system to identify 13,185 adult patients (>18 years) with T2DM from January 2008 to June 2013 and received a prescription for MF in combination with a sulfonylurea (SU; n = 9419), thiazolidinedione (TZD; n = 1846), dipeptidyl peptidase-4 inhibitor (DPP-4i; n = 1487), or a glucagon-like peptide-1 receptor agonist (GLP-1a; n = 433). Multivariate Cox models with propensity analysis were used to compare cohorts, with MF+SU serving as the comparator group.
Results: The mean (±SD) age was 60.6 ± 12.6 years, with 54.6% male and 75.8% Caucasians. The median follow-up was 4 years. There were 1077 deaths, 1733 CAD events, and 528 CHF events in 55,100 person-years of follow-up. A higher risk of CHF was observed with MF+DPP-4i use (hazard ratio [HR] 1.104; 95% confidence interval [CI] 1.04-1.17; P = 0.001). A trend towards improved overall survival for users of MF+TZD (HR 0.86; 95% CI 0.74-1.0; P = 0.05) and MF+GLP-1a (HR 0.569; 95% CI 0.30-1.07; P = 0.08) was observed. No significant differences in the risk of CAD were identified.
Conclusions: Consistent with recent studies, our results raise concern for an increased risk of CHF with use of DPP-4i.
(© 2015 Ruijin Hospital, Shanghai Jiaotong University School of Medicine and Wiley Publishing Asia Pty Ltd.)