Does metformin use decrease the risk of hospitalization and mortality from COVID-19?

This study assessed the link between metformin (Glucophage) use in hospitalized and non-hospitalized patients with diabetes and different outcomes due to coronavirus disease 2019 (COVID-19). The study showed that metformin use was associated with a protective effect in COVID-19 outcomes in patients with type 2 diabetes (T2D).

COVID-19 is caused by the SARS-CoV-2 virus which frequently affects patients with underlying conditions such as diabetes. The seriousness of COVID-19 is related to the production of cytokines (proteins made by different cells in the body that influence the immune response). Chronic inflammation observed in patients with T2D has been linked to insulin resistance and low levels of anti-inflammatory cytokines.

Metformin is usually the first line of treatment used with lifestyle modifications for managing T2D. It can suppress the immune response and has been suggested to affect a protein enzyme called adenosine monophosphate-activated protein kinase (AMPK). AMPK plays an important role in regulating viral infections. A few studies attempted to investigate the possible benefits of metformin use in reducing deaths in COVID-19 patients with T2D. However, due to the limited availability of data from these studies, more investigations are needed.

This study included 31,966 patients with at least two prescriptions for blood glucose controlling drugs, and who tested positive for SARS-CoV-2. 23,327 patients were metformin users while 8639 patients were non-users. Clinical outcomes measured were all-cause mortality, in-hospital mortality, hospitalization for COVID-19, and intensive care unit (ICU) submission. The average follow-up was 118 days (approximately 4 months).

Compared to non-metformin users, metformin users had a significantly reduced total mortality risk (by 30%) in-hospital mortality (by 32%), COVID-19 hospitalization (by 14%), and ICU admission (by 19%). 

The study indicated that metformin use in patients with T2D was associated with a lower risk of total mortality, in-hospital mortality, COVID-19 hospitalization, and ICU admission related to COVID-19.

The study did not obtain information on blood glucose control, body mass index, and HbA1c levels which can impact interpretations. Additionally, there was no available information on interruptions or switches to metformin use.