COVID-19 has been harmful to many aspects of human health. Recent research has highlighted how much more likely people are to have a heart attack or stroke in the years after recovering from COVID-19. Scientists are also working to learn more about long COVID, which has impacted millions of people, leaving many of them unable to work or function normally for weeks or months after being infected with SARS-CoV-2, the virus that causes COVID-19. One major challenge with understanding how long COVID is impacting people is the many symptoms it can cause. As many as 200 symptoms have been linked to long COVID.
Now, scientists have shown that COVID-19 can lead to chronic fatigue syndrome, or ME/CFS (myalgic encephalomyelitis/chronic fatigue syndrome). The hallmark of this disorder is the total exhaustion that follows exertion, sometimes immediately but also within a few hours. People with ME/CFS often have headaches, muscle pain, and a range of symptoms that affect the neurological and immunological functions of the body. It was estimated that prior to the pandemic, about 0.3 percent of the population suffered from ME/CFS, which can be triggered by viral infections such as Dengue or Epstein Barr. ME/CFS is also different from a syndrome that can persist after an infectious illness called post-infectious fatigue.
This research, which has been reported in Nature Communications, also identified another group of patients who had recovered from COVID-19 and have symptoms that are similar to ME/CFS. However, lab tests indicated that there are differences between this group and people who get ME/CFS after COVID-19, suggesting that while the symptoms are similar, these disorders are happening for different reasons from one patient to another.
"Suspicions that COVID-19 might trigger ME/CFS initially arose as early as during the first wave of the pandemic," said Professor Dr. Carmen Scheibenbogen, Acting Director of Charité's Institute of Medical Immunology. This is tough to prove, however, because right now there are standards, but no universally-accepted criteria for diagnosing ME/CFS, noted Scheibenbogen.
"Thanks to an extremely thorough diagnostic process and a comprehensive comparison with patients who developed ME/CFS following non-COVID-related infections, we have now been able to show that COVID-19 can trigger ME/CFS."
In this study, the researchers examined 42 people who were plagued by fatigue that disrupted their daily functions for six months after a case of COVID-19. Some of them could not work or could only barely care for themselves. While most of them had experienced a severe case of COVID-19, only three of these individuals had been hospitalized for it, and none had required supplemental oxygen. All of these infections happened during the pandemic's first wave, and none had been vaccinated.
The comparison group included people matched by age and gender who had been diagnosed with ME/CFS that followed an illness that was completely unrelated to COVID-19. The Canadian Consensus Criteria was used when diagnosing ME/CFS in this study, which is considered to be a reliable tool.
About half of the people who had recovered from COVID-19 were diagnosed with ME/CFS using this standard. The rest had milder symptoms. Some parameters were established during this testing.
In grip strength exercises, people with weaker abilities had high levels of a molecule called interleukin 8, an inflammatory cytokine. "In these cases, reduced muscular strength may be caused by a persistent inflammatory response," noted Scheibenbogen.
"In the ME/CFS group, however, hand grip strength was correlated with the hormone NT-proBNP, which can be released by muscle cells when oxygen supply is insufficient. This suggests that, in these individuals, muscle weakness may be caused by an impaired blood supply."
It may be possible to distinguish these groups based on the progression of disease as well. "In many people whose symptoms are indicative of ME/CFS but who do not meet diagnostic criteria, symptoms appear to improve over time," Scheibenbogen explained.
This study has indicated that ME/CFS is not psychosomatic, and is a real and severe disease that clinicians can measure and diagnose with objective methods, added Scheibenbogen. Right now, the current treatments for ME/CFS can only address symptoms, so Scheibenbogen is urging everyone, even younger people, to protect themselves from COVID-19 by getting vaccinated and wearing a proper mask.
Sources: Charité - Universitätsmedizin Berlin, Nature Communications
