Use of the drug metformin prior to a positive COVID-19 diagnosis appears to be protective against COVID-19 related death in patients with type 2 diabetes, according to research funded by the National Institutes of Health (NIH) and conducted at the University of Alabama at Birmingham. The findings were published January 13 by Frontiers in Endocrinology.
Increasing age and a number of co-morbidities such as hypertension, obesity and diabetes are associated with higher levels of mortality among those infected with COVID-19. While type 2 diabetes has become a recognized risk factor for a worse prognosis in patients with COVID-19, less is known about how anti-diabetic treatments impact upon mortality.
A team from the Hugh Kaul Precision Medicine Institute, University of Alabama, sought to determine the effects of different anti-diabetic treatments on mortality among an ethnically diverse population infected with COVID-19. The team retrospectively reviewed all electronic health records of subjects consecutively tested for COVID-19 between February and June 2020 at a single tertiary hospital in their area. In an effort to make the results more generalizable, the researchers included all patients within the five month period with the only exclusion criterion being a lack of available outcome data. The team sought to focus its attention on the diabetic treatments and in particular, insulin and metformin because these were the most commonly prescribed and there were too few patients prescribed other medicines to provide a meaningful statistical analysis. The primary outcome for the study was overall mortality, and the researchers used logistic regression to explore the association between mortality and known risk factors and diabetic treatments.
There were 604 patients who tested positive for COVID-19 during the study period. The majority of those testing positive (43%) were aged 50 to 70 years and just over half (51.5%) were Black African Americans, who had significantly higher odds of testing positive than those of white ethnicity (odds ratio, OR = 2.6). Overall mortality among those testing positive for COVID-19 was 11%, and the presence of diabetes dramatically increased the risk of mortality (OR = 3.62). In fact, 67% of all deaths occurred among those with diabetes.
Focusing on diabetic treatments, the researchers observed that use of metformin reduced the odds of dying by 62% (OR = 0.38) although no such effect was seen with insulin. Moreover, after adjusting for the covariates age, race, sex, obesity and hypertension status, the odds ratio for metformin remained significant (OR = 0.33). The researchers also observed that neither body mass index (BMI) or HBA1C levels were lower in those taking metformin, discounting these as explanatory factors.
The authors noted that while the presence of type 2 diabetes was associated with an increased mortality risk in those with COVID-19 (as reported in other studies) there appeared to be a protective effect among diabetic patients treated with metformin. They called for more research to understand how metformin conferred these effects.