Effects of insulin on cardiovascular events and all-cause mortality in patients with type 2 diabetes: A meta-analysis of randomized controlled trials

Aim: In 2019, the Italian Society of Diabetology and the Italian Association of Clinical Diabetologists nominated an expert panel to develop guidelines for drug treatment of type 2 diabetes. This expert panel, after identifying the effects of glucose-lowering agents on major adverse cardiovascular events (MACEs), all-cause mortality, and hospitalization for heart failure (HHF) as critical outcomes, decided to perform a systematic review and meta-analysis on the effect of insulin with this respect. Data synthesis: A MEDLINE database search was performed to identify all RCTs, up to June 1st, 2021, with duration≥52 weeks, in which insulin was compared with either placebo or active comparators. The principal endpoints were MACE and HHF (restricted for RCT reporting MACEs within their outcomes), all-cause mortality (irrespective of the inclusion of MACEs among the pre-specified outcomes). Mantel-Haenszel odds ratio (MH-OR) with 95% Confidence Interval (95% CI) was calculated for all the endpoints considered. Six RCTs (enrolling 8091 patients and 10,139 in the insulin and control group, respectively) were included in the analysis for MACEs and HF, and 18 in that for all-cause mortality (9760 and 11,694 patients in the insulin and control group, respectively). Treatment with insulin neither significantly increased nor reduced the risk of MACE, all-cause mortality, and HHF in comparison with placebo/active comparators (MH-OR: 1.09, 95% CI 0.97–1.23; 0.99, 95% CI 0.91, 1.08; and 0.90, 95% CI 0.78, 1.04, respectively). Conclusions: This meta-analysis showed no significant effects of insulin on incident MACE, all-cause mortality, and HHF.