Effect of metformin on all-cause mortality and major adverse cardiovascular events: An updated meta-analysis of randomized controlled trials

Aims: The Italian Society of Diabetology and the Italian Association of Clinical Diabetologists are developing new guidelines for drug treatment of type 2 diabetes. The effects of anti-hyperglycaemic drugs on all-cause mortality and major adverse cardiovascular events (MACEs) were included among the critical clinical outcomes. We have therefore carried out an updated meta-analysis on the effects of metformin on these outcomes. Data synthesis: A MEDLINE and EMBASE search was performed to identify all randomized controlled trials (RCTs) with duration >= 52 weeks (published up to August 2020), in which metformin was compared with either placebo/no therapy or active comparators. MACEs (restricted for RCT reporting MACEs within their study endpoints) and all-cause mortality (irrespective of the inclusion of MACEs among the pre-specified endpoints) were considered as the primary endpoints. Mantel-Haenszel odds ratio (MH-OR) with 95% confidence interval was calculated for all endpoints considered. Metformin was associated with a nonsignificant reduction of all-cause mortality (n = 13 RCTs; MH-OR 0.80 [95% CI 0.60, 1.07]). However, this association became statistically significant after excluding RCTs comparing metformin with sulfonylureas, SGLT-2 inhibitors or GLP-1 analogues (MH-OR 0.71 [0.51, 0.99]). Metformin was associated with a lower risk of MACEs compared with comparator treatments (n = 2 RCTs; MH-OR 0.52 [0.37, 0.73]), p < 0.001. Similar results were obtained in a post-hoc analysis including all RCTs fulfilling criteria for inclusion in the analysis (MH-OR: 0.57 [0.42, 0.76]). Conclusions: This updated meta-analysis suggests that metfomin is significantly associated with lower risk of MACEs and tendentially lower all-cause mortality compared to placebo or other anti-hyperglycaemic drugs. (C) 2020 The Italian Diabetes Society, the Italian Society for the Study of Atherosclerosis, the Italian Society of Human Nutrition and the Department of Clinical Medicine and Surgery, Federico II University. Published by Elsevier B.V. All rights reserved.