The authors collected and analyzed results from 45 different studies published in English between January 2020 and March 2021. The studies included a total of 9,751 patients diagnosed with COVID-19, 83% of whom had been hospitalized. Goodman added that there is little research available on post-COVID-19 symptoms among those with milder cases, but that two studies, reporting on 214 outpatients, showed high frequencies of persistent symptoms.
For their review, the authors defined persistent symptoms as those lasting for at least 60 days after diagnosis, symptom onset or hospital admission, or at least 30 days after recovery from acute illness or hospital discharge. The majority of the studies followed patients no more than three months, but a few followed patients for six months.
“We did this study because there have been a lot of news commentaries and scientific articles talking about long-term COVID symptoms,” Nasserie said. “But few had dug into the scientific evidence deeply enough to show the full range, how long they lasted and whom they affected.”
The authors found that 72.5% of study participants reported at least one persistent symptom. The rates were as high in two six-month studies. The symptoms indicated that a variety of systems within the body were affected, including cardiac, respiratory, neuromuscular, neurological, circulatory and immune systems, Nasserie said.
Shortness of breath, fatigue, sleep problems
The most commonly occurring symptoms were shortness of breath, fatigue, exhaustion and sleep problems. “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.” About 40% of patients said they experienced fatigue, 36% said they experienced shortness of breath and 29% said they experienced sleep disorders. Depression and anxiety, along with general pain and discomfort, were also relatively common: About 20% of patients described these symptoms. An inability to concentrate, commonly referred to as “brain fog,” was mentioned by about 25% of patients.
As an epidemiologist who studies patterns of disease, Goodman said he became increasingly concerned about the lingering effects of COVID-19 in early fall 2020 as news reports emerged of patients calling themselves “long haulers” and reporting a variety of unusual symptoms after recovering from the acute phase of the illness.
“Early on, we completely ignored the long-term consequences of getting sick with this virus,” Goodman said. “People were being told this was all in their heads. The question now isn’t is this real, but how big is the problem.”
Michael Hittle, a PhD student in epidemiology and clinical research at Stanford, also was a co-author on the study.
Stanford’s Department of Epidemiology and Population Studies supported the work.