As the world faces the possibility of another seasonal surge in coronavirus cases, medical experts are still mulling over the cause of long COVID.
The mysterious ailment causes a variety of symptoms long after the COVID-19 infection has cleared, including fatigue, loss of sexual desire, loss of smell and taste, chest pain and chronic cough.
Scientists still don’t know for sure what causes long COVID, the general term for about 200 widely varying symptoms.
But researchers at the University of Pennsylvania have suggested that reduced levels of serotonin (a neurotransmitter that affects mood, memory, sleep, digestion, blood clotting and sexual desire) could explain the persistent symptoms.
An estimated 10% to 30% of people have experienced some form of long COVID after recovering from a coronavirus infection, a risk that has decreased somewhat since the start of the pandemic.
To investigate the role serotonin might play, researchers analyzed the blood of 58 patients who had been experiencing long COVID for up to 22 months since their infection.
Long COVID symptoms may include fatigue, loss of sexual desire, loss of smell and taste, chest pain, and chronic cough.Georgii – stock.adobe.com
Those results were compared with those of 30 people without post-COVID symptoms and those of 60 patients who were in the early stage of coronavirus infection.
Their analysis revealed that serotonin levels were altered immediately after a coronavirus infection, something that also occurs after other viral infections. But in people with long COVID, serotonin was the only molecule that did not recover to pre-infection levels.
Reduced serotonin levels disrupt the vagus nervous system, which transmits signals between the body and the brain.
Serotonin plays a role in short-term memory and researchers proposed that depleted serotonin could lead to memory problems and other cognitive problems that affect people with long COVID.
“Although not everyone experiences difficulties in the serotonin pathway, at least a subset may respond to therapies that activate this pathway,” said Dr. Christoph Thaiss, senior author of the study and assistant professor at the Perelman School of Medicine. the University of Pennsylvania, told the New York Times.
Low levels of serotonin, shown here in the gastrointestinal tract, could explain some symptoms of long COVID.Semantic Scholar
If low serotonin levels are to blame for long COVID, some researchers hope that increasing those levels may help.
“If we supplement serotonin or prevent its degradation, perhaps we can restore some of the vagal signals and improve memory and cognition,” said Dr. Maayan Levy, senior author and assistant professor of microbiology at the Perelman School of Medicine.
To this end, Levy and Thaiss are planning a clinical trial to test fluoxetine, a selective serotonin reuptake inhibitor (SSRI) marketed as Prozac. The trial would join other tests currently underway to solve the mystery of long COVID.
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Source: vtt.edu.vn