If you land in the hospital with a COVID-19 infection, there's a good chance you'll still be suffering symptoms months later, researchers report.

A wide swath of lingering health issues plagued more than 70% of these patients, investigators found.

"Early on, we completely ignored the long-term consequences of getting sick with this virus," said study senior author Dr. Steven Goodman, a professor of epidemiology and population health and medicine at Stanford University. "People were being told this was all in their heads. The question now isn't is this real, but how big is the problem."

To determine that, his team analyzed 45 studies that were published between January 2020 and March 2021. The studies included more than 9,700 COVID-19 patients. Of those, 83% had been hospitalized.

They found that 72.5% of study participants reported still having at least one of 84 persistent symptoms or clinical signs, with the most common being fatigue (40%), shortness of breath (36%), sleep disorders (29%), inability to concentrate (25%), depression and anxiety (20%), and general pain and discomfort (20%).

Other problems reported by patients included loss of taste and smell, memory loss, chest pain and fevers.

Persistent symptoms were defined as those lasting at least 60 days after diagnosis, symptom onset or hospital admission, or at least 30 days after recovery from acute illness or hospital discharge.

If even a portion of these patients require continuing care, they could pose an immense public health burden, said Goodman.

"If something on the order of 70% of those coming out of moderate to serious COVID-19 are showing persisting symptoms, that is a huge number," Goodman said in a Stanford news release. "It's astonishing how many symptoms are part of what's now being referred to as long COVID."

The study was published May 26 in the journal JAMA Network Open.

"We did this study because there have been a lot of news commentaries and scientific articles talking about long-term COVID symptoms," said study lead author Tahmina Nasserie, a graduate student in epidemiology at Stanford.

"But few had dug into the scientific evidence deeply enough to show the full range, how long they lasted and whom they affected," she noted in the release.

"The numbers are very shocking, especially for fatigue and shortness of breath," Nasserie said. "These were pretty debilitating symptoms, with some people reporting difficulty walking up a flight of stairs."