NEW YORK (NYTIMES) - More than three-quarters of Americans diagnosed with long Covid-19 were not sick enough to be hospitalised for their initial infection, a new analysis of tens of thousands of private insurance claims reported Wednesday (May 18).
The researchers analysed 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 US healthcare 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 10-30 per cent of infected adults; a recent report from the US 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 hospitalised 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 hospitalised 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 programmes 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 non-profit organisation that focuses on health care costs and insurance issues, found that 76 per cent of the long Covid patients did not require hospitalisation for their initial coronavirus infection.
Another striking finding was that while two-thirds of the patients had preexisting health conditions in their medical records, nearly one-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 Ms Robin Gelburd, president of Fair Health, said that the organisation 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 organisation also plans to analyse 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 4 1/2 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 per cent of the patients were between ages 36-50, while nearly one-third were ages 51-64, and 17 per cent were ages 23-35. Children were also diagnosed with post-Covid conditions: Nearly 4 per cent of the patients were 12 or younger, while nearly 7 per cent were between ages 13-22.
Six per cent of the patients were 65 and older, a proportion that most likely reflects the fact that patients covered by the regular Medicare programme were not 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 analysed did not include information about the race or ethnicity of patients, researchers said.
The analysis, which Ms Gelburd said was evaluated by an independent academic reviewer but not formally peer-reviewed, also calculated a risk score for the patients, a way of estimating how likely people are to use health care resources.
Comparing all the insurance claims the patients had up until 90 days before they contracted Covid with their claims 30 days or more after they were infected, the study found that average risk scores went up for patients in every age group.
Ms Gelburd and other experts said the scores suggested that the repercussions of long Covid are not simply confined to increased medical spending.
They signal "how many people are leaving their jobs, how many are being given disability status, how much absenteeism is there in school," Ms Gelburd said. "It's like a pebble thrown into the lake, and these ripples circling that pebble are concentric circles of impact."
Because the study captured only a privately insured population, Dr Ssentongo said, it almost certainly understates the scope and burden of long Covid, especially since low-income communities have been disproportionately affected by the virus and often have less access to health care.
"I think it may even be worse if we added in the Medicaid population and all these other people that would have been missed" in the study's data, he said.
Sixty per cent of the patients with the post-Covid diagnosis were female, the study reported, compared with 54 per cent of Covid patients overall in the Fair Health database. In the oldest and youngest age groups, however, there were roughly as many males as females.
"I think there is a female preponderance in terms of this condition," Dr Steves said, adding that the reasons could include differences in biological factors that make women more prone to autoimmune conditions.
The insurance claims showed that nearly one-quarter of the post-Covid patients had respiratory symptoms; nearly one-fifth had coughs; and 17 per cent had been diagnosed with malaise and fatigue, a far-reaching category that could include issues like brain fog and exhaustion that get worse after physical or mental activity. Other common issues included abnormal heartbeats and sleep disorders.