Metformin use is associated with a reduced risk of mortality in patients with diabetes hospitalised for COVID-19

Abstract : AIMS: Metformin exerts anti-inflammatory and immunosuppressive effects. We addressed the impact of prior metformin use on prognosis in patients with type 2 diabetes hospitalised for COVID-19. METHODS: CORONADO is a nationwide observational study that included patients with diabetes hospitalised for COVID-19 between March 10 and April 10, 2020 in 68 French centres. The primary outcome combined tracheal intubation and/or death within 7 days of admission. A Kaplan-Meier survival curve was reported for death up to day 28. The association between metformin use and outcomes was then estimated in a logistic regression analysis after applying a propensity score inverse probability of treatment weighting approach. RESULTS: Among the 2449 patients included, 1496 were metformin users and 953 were not. Compared with non-users, metformin users were younger with a lower prevalence of diabetic complications, but had more severe features of COVID-19 on admission. The primary endpoint occurred in 28.0% of metformin users (vs 29.0% in non-users, P =  0.6134) on day 7 and in 32.6% (vs 38.7%, P = 0.0023) on day 28. The mortality rate was lower in metformin users on day 7 (8.2 vs 16.1%, P \textless  0.0001) and on day 28 (16.0 vs 28.6%, P \textless 0.0001). After propensity score weighting was applied, the odds ratios for primary outcome and death (OR [95%CI], metformin users vs non-users) were 0.838 [0.649-1.082] and 0.688 [0.470-1.007] on day 7, then 0.783 [0.615-0.996] and 0.710 [0.537-0.938] on day 28, respectively. CONCLUSION: Metformin use appeared to be associated with a lower risk of death in patients with diabetes hospitalised for COVID-19.