Is there an association between metformin use and clinical outcomes in diabetes patients with COVID-19?

AIM: Previous studies have reported inconsistent results regarding the association between metformin use and clinical outcomes in diabetes mellitus (DM) patients with coronavirus disease 2019 (COVID-19). This study aimed to evaluate the association between metformin use and clinical outcomes in DM patients with COVID-19. METHODS: This retrospective study was based on claims data. All diseases, including COVID-19, were defined using International Classification of Diseases 10th Revision (ICD-10) codes. Patients were divided into three groups depending on metformin use: CON (those not taking DM medication); N-MFOM (those taking DM medications other than metformin); and MFOM (those taking metformin for DM). Ultimately, 1865 patients were included; CON, N-MFOM and MFOM groups comprised 1301, 95 and 469 patients, respectively. RESULTS: Kaplan–Meier analyses showed that MFOM patients had poorer survival rates than those in the CON group, but there were no significant differences in survival rates between MFOM and N-MFOM groups. Multivariate Cox regression analyses revealed more favourable survival in CON than in N-MFOM patients, but there was no statistically significant difference in MFOM vs the other groups. Also, there were no significant differences in rates of use of inotropes, extracorporeal membrane oxygenation, conventional oxygen therapy, high-flow nasal cannulas or mechanical ventilators, nor in the rates of acute kidney injury or cardiac events across all study groups. CONCLUSION: No definite association could be found between metformin use and clinical outcomes, including survival. However, given the disproportionate participant numbers in our groups and small number of events, further studies are needed to determine whether the use of metformin has favourable or unfavourable effects in DM patients with COVID-19.