The study was conducted by researchers from the University of Minnesota, and the paper was published in the international medical journal The Lancet Infectious Diseases in June.
Long COVID refers to persistent discomfort for weeks or months after being infected with COVID-19. Common symptoms include fatigue, shortness of breath, cognitive impairment, headache, chest pain, and joint pain, among others, which affect daily life.
Through remote recruitment, the researchers screened 1,126 participants who agreed to long-term follow-up. They were overweight and obese people aged 30 to 85, had symptoms of COVID-19 infection for fewer than seven days, tested positive for COVID within three days of trial enrollment, and had no previous known SARS-CoV-2 infection.
In this randomized trial, about half of the participants took metformin, and the other half took a placebo. They were also randomly assigned to receive either ivermectin, fluvoxamine, or placebo.
After 300 days of follow-up, 10.4 percent of participants who took the placebo were diagnosed with long COVID, while 6.3 percent who took metformin were also diagnosed.
The results of the study showed that taking metformin reduced the risk of developing long COVID by 41 percent. In subjects who took metformin within three days of symptom onset, the risk of developing long COVID was reduced by 63 percent.
The study also proved that taking metformin reduced the risk of developing long COVID in people infected during the peak period of the three SARS-CoV-2 variants, Alpha, Delta, and Omicron.
However, the study found that taking ivermectin or fluvoxamine showed no signs of protection against long COVID.
Metformin, originally developed from the French lilac (Galega officinalis), is inexpensive and has no significant side effects. For decades, it has been the drug of choice for Type 2 diabetes treatment worldwide.
Researchers believe metformin could be used as a therapeutic drug for outpatients infected with COVID-19. It has the merits of proven clinical efficacy, is available all over the world at a low cost, and is safe to use
It is important to note that the trial did not demonstrate whether metformin was effective in preventing COVID-19 in patients requiring emergency treatment or hospitalization due to COVID-19, nor did it prove that metformin was effective in people who already had long COVID.
The study is not without its limitations. First, there is an obvious sample selection bias, because the people who participated in the clinical trial and completed the 10-month follow-up survey may not represent the general population affected by COVID-19 and long COVID. The trial also excluded low-risk groups for severe COVID-19, namely adults with a normal body mass index (BMI), and people under the age of 30. Whether the above findings apply to these groups remains to be seen.
