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  Conclusion Metformin use appeared to be associated with a lower risk of death in patients with diabetes hospitalised for COVID-19.