According to a study carried out by the researchers at the University of Alabama at Birmingham, use of the diabetes drug metformin -- before a diagnosis of Covid-19 -- is associated with a threefold decrease in mortality in Covid-19 patients with Type 2 diabetes.
Lead author Anath Shalev, M.D., director of UAB's Comprehensive Diabetes Center, said: "This beneficial effect remained, even after correcting for age, sex, race, obesity, and hypertension or chronic kidney disease and heart failure."
"Since similar results have now been obtained in different populations from around the world -- including China, France, and a UnitedHealthcare analysis -- this suggests that the observed reduction in mortality risk associated with metformin use in subjects with Type 2 diabetes and Covid-19 might be generalizable," Shalev added.
However, the researchers are yet to find how metformin improves prognosis in the context of Covid-19.
The findings suggest that the mechanisms may go beyond any expected improvement in glycemic control or obesity. The researchers have noticed that neither body mass index, blood glucose nor haemoglobin A1C was lower in the metformin users who survived than those who died.
"The mechanisms may involve metformin's previously described anti-inflammatory and anti-thrombotic effects," Shalev said.
The study, published in the journal MedRxiv and Frontiers in Endocrinology, involved 25,326 patients tested for Covid-19 at the tertiary care UAB Hospital between February 25 and June 22, 2020.
The study found that 93 per cent of deaths occurred in subjects over the age of 50. This was more common among males or people with high blood pressure. Diabetes was associated with a dramatic increase in mortality, with an odds ratio of 3.62. Overall, 67 per cent of deaths in the study occurred in subjects with diabetes.
The researchers looked at the effects of diabetes treatment on adverse Covid-19 outcomes. They focused on insulin and metformin as the two most common medications for Type 2 diabetes. They found that prior insulin use did not affect mortality risk.
However, the use of metformin significantly reduced the odds of dying. The 11 per cent mortality for metformin users was not only comparable to that of the general Covid-19-positive population. It was dramatically lower than the 23 per cent mortality for diabetes patients not on metformin.
Notably, death was significantly less likely -- with an odds ratio of 0.33 -- for Type 2 diabetes subjects taking metformin, compared with those who did not take metformin.