Thatâ€™s the key takeaway from a fresh look at patients who continue to struggle with severe fatigue, poor sleep, brain fog, muscle aches and pains long after their initial -- and often mild -- COVID infection has otherwise resolved.
Researchers found that nearly half of the 41 post-COVID patients they studied suffered from the sort of fever, aches, fatigue and depression symptoms that have long been associated with chronic fatigue, also known as myalgic encephalomyelitis/chronic fatigue syndrome.
Chronic fatigue is a medically unexplained illness characterized by severe fatigue that has limited a patientâ€™s normal daily activity for at least six months, according to study author Dr. Donna Mancini, a professor at the Icahn School of Medicine at Mount Sinai in New York City.
"It is usually accompanied by vague symptoms, such as unrefreshing sleep, post-exertional malaise -- a worsening of symptoms following physical or mental efforts -- mental fogginess, dizziness, muscle aches and sore throat," she said.
The U.S. Centers for Disease Control and Prevention estimates between 800,000 to 2.5 million Americans are affected by chronic fatigue syndrome. Roughly a third develop it after a viral illness.
"[Still], we were surprised to find that nearly 50% of the patients we studied met criteria for chronic fatigue syndrome," Mancini said.
Patients in the new study were between 23 and 69 years of age. Between three and 15 months out from their initial COVID diagnosis all were considered long-haulers, meaning that despite their COVID recovery, they suffered from a constellation of lingering health issues.
All were left with what Mancini described as a "persistent unexplained shortness of breath." In 9 out of 10 patients, that included hyperventilation and/or the kind of rapid breathing during exercise that is normally associated with asthma.
Though not uncommon among long-haulers, such breathing issues were deemed "unexplained" because they typically owe to COVID-inflicted lung or heart damage, and neither was apparent among any of the study participants. In fact, many had had relatively mild cases of COVID that didn't require hospitalization or treatment.
To better understand what could be driving their symptoms, the researchers conducted tests to assess their breathing patterns during exercise and typical daily routines.
Participants were also asked to indicate patterns of fatigue over the prior half-year, as well as any joint stiffness, muscle aches, sleep and concentration problems, and exertion-related issues.
In all, 46% had developed post-COVID chronic fatigue, the study found. And that's a troubling finding, Mancini said, given that in many cases, the initial COVID infection was not life-threatening or even all that serious.
Her conclusion: "Basically anyone who has COVID is at risk."
That concern is shared by Dr. Colin Franz, an assistant professor of physical medicine and rehabilitation and neurology at Northwestern Universityâ€™s Feinberg School of Medicine in Chicago, who reviewed the findings.
While researchers try to define this problem, between 0.5% and 1% of non-hospitalized COVID patients develop at least one long-haul symptom, he said. "Given the vast number of people who had COVID worldwide, this represents millions of people," Franz said.
In fact, most people who develop long-haul COVID issues were never that ill with COVID itself, he added.
"As someone who sees several post-COVID patients per week with persistent shortness of breath concerns, I am not surprised by these findings," Franz said, "although I think many of my colleagues might be who donâ€™t see a lot of post-COVID long-haulers."
Franz said he was skeptical at first when he heard of persistent symptoms in patients whose COVID infection did not put them in the hospital.
"But my involvement in our post-COVID clinical rehabilitation program has convinced me this is a really common problem," he added.
The new findings were published in the December issue of JACC: Heart Failure.
There's more about long-haul COVID at the U.S. Centers for Disease Control and Prevention.