More than three-quarters of Americans diagnosed with long Covid were not sick enough to be hospitalized for their initial infection, a new analysis of tens of thousands of private insurance claims reported on Wednesday.
The researchers analyzed data from the first few months after doctors began using a special diagnostic code for the condition that was created last year. The results paint a sobering picture of long Covid’s serious and ongoing impact on people’s health and the American health care system.
Long Covid, a complex constellation of lingering or new post-infection symptoms that can last for months or longer, has become one of the most daunting legacies of the pandemic. Estimates of how many people may ultimately be affected have ranged from 10 percent to 30 percent of infected adults; a recent report from the U.S. Government Accountability Office said that between 7.7 million and 23 million people in the United States could have developed long Covid. But much remains unclear about the prevalence, causes, treatment and consequences of the condition.
The new study adds to a growing body of evidence that, while patients who have been hospitalized are at greater risk for long Covid, people with mild or moderate initial coronavirus infections — who make up the vast majority of coronavirus patients — can still experience debilitating post-Covid symptoms including breathing problems, extreme fatigue and cognitive and memory issues.
“It’s generating a pandemic of people who were not hospitalized, but who ended up with this increased disability,” said Dr. Paddy Ssentongo, an assistant professor of infectious disease epidemiology at Penn State, who was not involved in the new study.
The analysis, based on what the report calls the largest database of private health insurance claims in the United States, found 78,252 patients who were diagnosed with the new code from the International Classification of Diseases — diagnostic code U09.9 for “Post COVID-19 condition, unspecified” — between Oct. 1, 2021, and Jan. 31, 2022.
Dr. Claire Steves, a clinical academic and physician at King’s College London, who was not involved in the new research, said the overall number of people who received the diagnosis was “huge,” given that the study covered only the first four months after the diagnostic code was introduced and did not include people covered by government health programs like Medicaid or Medicare (though it did include people in private Medicare Advantage plans). “That’s probably a drop in the ocean compared to what the real number is,” Dr. Steves said.
The study, conducted by FAIR Health, a nonprofit organization that focuses on health care costs and insurance issues, found that 76 percent of the long Covid patients did not require hospitalization for their initial coronavirus infection.
Another striking finding was that while two-thirds of the patients had pre-existing health conditions in their medical records, nearly a third did not, a much larger percentage than Dr. Ssentongo said he would have expected. “These are people who have been healthy and they’re like, ‘Guys, something is not right with me,’” he said.
The researchers plan to continue to track the patients to see how long their symptoms last, but Robin Gelburd, the president of FAIR Health, said that the organization decided to publish data from the first four months now, “given the urgency” of the issue.
She said researchers were working to try to answer some of the questions that are not addressed in the report, including providing detail on some patients’ previous health conditions to try to identify whether certain medical problems put people at higher risk of long Covid.
The organization also plans to analyze how many patients in the study were vaccinated and when, Ms. Gelburd said. More than three-quarters of the patients in the study were infected in 2021, most of those in the last half of the year. On average, patients were still experiencing long Covid symptoms that qualified for the diagnosis four and a half months after their infection.
The findings suggest a potentially staggering impact of long Covid on people in the prime of their lives, and on society at large. Nearly 35 percent of the patients were between the ages of 36 to 50, while nearly one-third were ages 51 to 64, and 17 percent were ages 23 to 35. Children were also diagnosed with post-Covid conditions: Nearly 4 percent of the patients were 12 or younger, while nearly 7 percent were between ages 13 and 22.
Six percent of the patients were 65 and older, a proportion that most likely reflects the fact that patients covered by the regular Medicare program weren’t included in the study. They were much more likely than the younger groups with long Covid to have had pre-existing chronic medical conditions.
The insurance data analyzed did not include information about the race or ethnicity of patients, researchers said.