Metformin was associated with lower all-cause mortality in type 2 diabetes with acute coronary syndrome: A Nationwide registry with propensity score-matched analysis

Background: No randomized controlled trials evaluating metformin therapy efficacy in patients with type 2 diabetes mellitus (DM) and acute coronary syndrome (ACS) have been reported. We aimed to examine the mortality benefit of metformin therapy in patients with type 2 DM and ACS, compared with non-metformin anti-diabetes agents users. Methods: Data were extracted from the prospective nationwide ACS-DM Taiwan Society of Cardiology registry. Propensity score (PS) matching on baseline characteristics and treatment measures was performed for metformin versus non-metformin users. The Cox proportional hazards model was used to compare mortality outcomes among the PS-matched cohort as the primary analysis. The Cox proportional hazards models adjusting for all pre-determined covariates and quintiles of the PS among the overall population were performed as the secondary analyses. Results: Of 1157 patients with type 2 DM and ACS receiving anti-diabetes agents, 78 patients (6.7%) died over the 2-year follow-up period. After PS matching, 318 metformin users were matched with 318 non-metformin users. Metformin users had a lower all-cause mortality rate (adjusted hazard ratio [aHR] 0.50, 95% confidence interval [CI] 0.26–0.95) in the primary analysis. The survival benefit of metformin therapy was consistent in the secondary analyses (aHR 0.30, 95% CI 0.17–0.54 while adjusting for all pre-determined covariates, and aHR 0.34, 95% CI 0.19–0.59 while adjusting for quintiles of the PS). Conclusions: Among patients with type 2 DM and ACS, metformin was associated with lower all-cause mortality. However, a detrimental effect of any of the comparators could not be excluded.