MMR September 27 2023 - Chief Joint

More than three years into the pandemic, the millions of people who have suffered from long Covid finally have scientific proof that their condition is real.



Scientists have found clear differences in the blood of people with long Covid — a key first step in the development of a test to diagnose the illness.



The findings, published Monday in the journal Nature, also offer clues into what could be causing the elusive condition that has perplexed doctors worldwide and left millions with ongoing fatigue, trouble with memory and other debilitating symptoms.



The research is among the first to prove that "long Covid is, in fact, a biological illness," said David Putrino, principal investigator of the new study and a professor of rehabilitation and human performance at the Icahn School of Medicine at Mount Sinai in New York.



Dr. Marc Sala, co-director of the Northwestern Medicine Comprehensive Covid-19 Center in Chicago, called the findings "important." He was not involved with the new research.



"This will need to be investigated with more research, but at least it's something because, quite frankly, right now we don't have any blood tests" either to diagnose long Covid or help doctors understand why it's occurring, he said.



Putrino and his colleagues compared blood samples of 268 people. Some had Covid but had fully recovered, some had never been infected, and the rest had ongoing symptoms of long Covid at least four months after their infection.



Several differences in the blood of people with long Covid stood out from the other groups.



The activity of immune system cells called T cells and B cells — which help fight off germs — was "irregular" in long Covid patients, Putrino said. One of the strongest findings, he said, was that long Covid patients tended to have significantly lower levels of a hormone called cortisol.



A major function of the hormone is to make people feel alert and awake. Low cortisol could help explain why many people with long Covid experience profound fatigue, he said.



"It was one of the findings that most definitively separated the folks with long Covid from the people without long Covid," Putrino said.



The finding likely signals that the brain is having trouble regulating hormones. The research team plans to dig deeper into the role cortisol may play in long Covid in future studies.



Meanwhile, doctors do not recommend simply boosting a person's cortisol levels in an attempt to "fix" the problem.