It’s been well known since early in the COVID-19 pandemic that people with diabetes have a higher risk of poor outcomes if they get the viral infection — including higher rates of hospitalization, admission to the intensive care unit (ICU) and death. It’s also been well established since then that good blood glucose control is very important to reduce the risk of poor outcomes associated with diabetes — both before people are hospitalized with COVID-19, and once they’re in the hospital.
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Because of the higher risk that people with diabetes face if they get COVID-19, doctors have been wondering if there are any steps that can be taken to reduce this risk preemptively — before people with diabetes develop the infection. According to a new study, one treatment that may be highly protective against poor outcomes in COVID-19 — including death — is one that many people with diabetes already receive: the common diabetes drug metformin.
Lower death risk across diverse population
The study, published in the journal Frontiers in Endocrinology, was conducted between February and June 2020 at a the University of Alabama at Birmingham hospital, which serves a racially diverse population. A total of 25,326 people were tested for COVID-19 during the study period, turning up 604 positive results. The researchers wrote that this low rate of COVID-19 positivity was most likely due to the fact that people who came to the hospital for elective procedures were tested. This wide testing “net” means that people who tested positive for COVID-19 weren’t just those hospitalized for severe illness.
One notable finding was that African-Americans were much more likely to test positive for COVID-19 than whites. While African-Americans make up 26% of the population in Alabama, they accounted for 52% of those who tested positive. White people made up 36% of those who tested positive. Among those who tested positive, 70% had preexisting hypertension, 61% were obese and 41% had diabetes. Among those with diabetes, 92% had hypertension, and 74% were obese.
Overall, people with hypertension were 2.46 times as likely to test positive for COVID-19 than the overall population in the study, while those with diabetes were 2.11 times as likely to test positive. Those with diabetes who tested positive for COVID-19 were much more likely to die during the study period, with 45 out of 239 people (18.8%) dying — making them 3.62 times as likely to die as the overall group of people who tested positive for COVID-19. This higher likelihood of dying was still present after the researchers adjusted for differences in age, race, sex, obesity and hypertension.
But one factor emerged in people with diabetes that was associated with a reduced risk of death — taking metformin prior to testing positive for COVID-19. Those who took metformin were only 0.33 times as likely to die as the overall group of people with diabetes, once the researchers adjusted for other differences — with eight out of 76 people (10.5%) who took metformin dying. In fact, the researchers pointed out that the COVID-19 death rate for metformin users was similar to that of people without diabetes — and much lower than the death rate seen in people with diabetes who didn’t take metformin, with 34 out of 144 people (23.6%) dying.
Is metformin actually protective?
Since this study was observational — meaning that it simply looked at different characteristics and outcomes, rather than actively testing treatments as in a clinical trial — there’s no way to know for sure whether taking metformin was responsible for the lower death rate seen in people who took the drug. It’s possible that some underlying factor, or factors, that led to people being prescribed metformin — rather than another diabetes treatment — was also responsible for the lower risk of death. But the lower death rate associated with metformin was still seen after people with chronic kidney disease or heart failure were excluded from the analysis — conditions that typically mean a person can’t take metformin. This means it’s highly unlikely that the lower death rate associated with metformin was due to the group being skewed in favor of healthier people who didn’t have these conditions.
What’s more, the researchers noted that people who took metformin in the study weren’t any healthier at the outset than those who didn’t take the drug, based on their body-mass index (BMI, a measure of weight that takes height into account) or A1C level (a measure of long-term blood glucose control).
It isn’t known how, exactly, metformin might reduce the risk of death from COVID-19. But the study’s results are consistent with early Chinese and French reports on COVID-19 outcomes, which also found a lower risk of death associated with taking the drug. At the very least, the researchers write, these findings mean that it’s important for people who take metformin not to delay or discontinue taking the drug during the COVID-19 pandemic.
Want to learn more about coronavirus and diabetes? Read our latest COVID-19 updates.