Consuming metformin, a safe, affordable and widely-available diabetes medication, for two weeks after being infected with SARS-CoV-2, reduces the risk of developing long Covid by 40 per cent over the 10 months following infection, says a study published June 9 (Indian local time) in the journal The Lancet Infectious Diseases. When the symptoms of Covid-19 persist in a patient for weeks, months, and even a year, in spite of testing negative for the virus, the condition is known as long Covid. There are no proven treatments for long Covid. Also, the only way to prevent the condition is to reduce the risk of Covid-19 infection.
More than 65 million people worldwide have long Covid, according to a January 2023 study published in Nature Reviews Microbiology.
The new study published in The Lancet Infectious Diseases marks the first phase 3 randomised controlled trial of a treatment for patients that shows the risk of long Covid after testing positive for SARS-CoV-2 can be reduced by taking a certain medication.
In a Lancet statement, Dr Carolyn Bramante from the University of Minnesota Medical School, and the first author on the paper, said long Covid is a public health emergency impacting the physical health, mental health and economy, especially in socioeconomically marginalised groups, and there is an urgent need to find potential ways to prevent the disease. She explained that the study showed that metformin substantially reduces the risk of being diagnosed with long Covid if taken when first infected with SARS-CoV-2. However, the trial does not indicate whether metformin would be effective as a treatment for people who already have long Covid.
How the study was conducted
The study authors selected participants who were not hospitalised, were above 30 years of age, were at a higher risk of severe Covid-19 because of being overweight, and had tested positive for SARS-CoV-2 within the last three days, but were not previously infected with the novel coronavirus. The authors recruited 1,126 participants for the trial from December 2020 to January 2022. The participants were given either metformin, or an identical placebo pill.
As many as 564 participants were given metformin, and 562 were given a placebo.
The authors conduct follow-up studies of the participants for 10 months, gathering information through self-report questionnaires every 30 days.
What the study found
More than 40 per cent of long Covid cases were prevented using metformin. Of the 564 participants given metformin, 35 reported a long Covid diagnosis within 10 months of follow up. They accounted for 6.3 per cent of the participants who received metformin. Of the 562 participants who received a placebo, 58 reported a long Covid diagnosis within 10 months of follow-up. They accounted for 10.4 per cent of the participants who received a placebo. Therefore, metformin prevented more than 40 per cent of long Covid cases.
Previously published results from the trial also showed that metformin prevented more than 40 per cent of emergency department visits, hospitalisations, and deaths due to Covid-19 within two weeks of starting the treatment, compared to a placebo.
The trial also involved testing drugs such as ivermectin and fluvoxamine. Neither drug prevented long Covid.
How metformin may have prevented long Covid
In the statement, David Odde from the University of Minnesota, and a co-author on the paper, explained that a possible reason behind the reduction in both severe Covid-19 and long Covid diagnosis seen in the trial is that metformin stops the replication of SARS-CoV-2 in the lab, as shown by previous studies, and the authors' predictions from mathematical modelling of viral replication.
Limitations to the study
Some of the limitations to the study include the fact that the trial excluded those with a body mass index less than 25 years, and those younger than 30 years, which is why it is not known whether the same results will be seen in those populations.