People with type 2 diabetes who develop COVID-19 show a substantially reduced risk of dying if they are taking metformin, shows a study that adds to prior research indicating the drug might somehow play a role in reducing the severity of infection.
“Unlike several previous analyses, this was a study in a racially diverse population with a high proportion of Blacks/African Americans and [it] revealed that metformin treatment of diabetes prior to diagnosis with COVID-19 was associated with a dramatic threefold reduced mortality in subjects with type 2 diabetes, even after correcting for multiple covariates,” first author Anath Shalev, MD, of the Comprehensive Diabetes Center at the University of Alabama at Birmingham, said in an interview.
But Anne Peters, MD, a professor of clinical medicine at the University of Southern California, Los Angeles, said caution is needed when interpreting these findings.
“It’s hard to tease out the true effects because, for instance, those treated with insulin may be a sicker subset of patients with diabetes than those on metformin, or those with comorbidities such as renal insufficiency may not be treated with metformin” she said in an interview.
“In general, though, treatment obviously matters and people who are better treated tend to do better, so while I think this study raises the question of what role metformin plays in the risk of mortality and COVID-19, I don’t think it necessarily proves the association,” Dr. Peters asserted.
Diverse population
The new study, published this month in Frontiers of Endocrinology, included 25,326 individuals who were tested for COVID-19 at the University of Alabama at Birmingham Hospital between February and June 2020.
Overall, 2.4% tested positive for COVID-19 (n = 604), which the authors note is likely a low figure because screening included asymptomatic hospital staff and patients having elective procedures.
Black/African American patients had a significantly higher risk of COVID-19 positivity, compared with White patients (odds ratio, 2.6; P < .0001). Rates were also higher among those with hypertension (OR, 2.46), diabetes (OR, 2.11), and obesity (OR, 1.93), compared with those without each condition (all P < .0001).
The overall mortality rate in COVID-19-positive patients was 11%. Diabetes was associated with a dramatically increased risk of death (OR, 3.62; P < .0001), and remained an independent risk factor even after adjusting for age, race, sex, obesity, and hypertension.
Notably, the reduction in mortality among those with diabetes taking metformin prior to COVID-19 diagnosis was significant: 11% of those patients died, compared with 23% of those with diabetes not taking metformin (OR, 0.33; P = .021).
Similar findings reported across varied populations
The study adds to mounting research suggesting metformin could have a protective effect on COVID-19 mortality, including an early report from Wuhan, China, findings from the French CORONADO study, and a U.S. study linking treatment with decreased mortality among women with COVID-19.
Of note, the effects of metformin on mortality in the current study were observed in men and women alike, as well as in high-risk subgroups including African Americans.
“The fact that such similar results were obtained in different populations from around the world suggests that the observed reduction in mortality risk, associated with metformin use in subjects with type 2 diabetes and COVID-19, might be generalizable,” the authors wrote.
“Furthermore, these findings underline the importance of following general diabetes treatment and prevention guidelines and not delaying or discontinuing any metformin treatment,” they add.