The study’s findings were a mix of good and bad news, said Paul Harrison, a professor of psychiatry at Oxford University and the study’s senior author. Among the reassuring aspects was the rapid resolution of symptoms such as depression and anxiety.
“I was surprised and relieved at how quickly the psychiatric sequelae subsided,” Harrison said.
David Putrino, director of rehabilitation innovation at Mount Sinai Health System in New York, who has been studying the lasting impacts of the coronavirus since the start of the pandemic, said the study revealed some very troubling results.
“This allows us to see without a doubt the occurrence of significant neuropsychiatric consequences in individuals who had Covid and much more often than those who did not,” he said.
Because it focused only on the neurological and psychiatric effects of the coronavirus, the study’s authors and others pointed out that it is not strictly long-term research on Covid.
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“It would be overreaching and unscientific to make the immediate assumption that everyone in [study] group had a long time of Covid,” Putrino said. But the study, he said, “informs long-standing research on Covid.”
Between 7 million and 23 million people in the United States, according to the latest government estimates, have long-term Covid — a catch-all term for a wide range of symptoms including fatigue, shortness of breath and anxiety that persist weeks and months after the acute infection has calmed down. These numbers are expected to increase as the coronavirus is established as an endemic disease.
The study was led by Maxime Taquet, a senior researcher at Oxford University who specializes in using big data to shed light on psychiatric disorders.
The researchers compared almost 1.3 million patients diagnosed with Covid-19 between January 20, 2020 and April 13, 2022, with an equal number of patients who had other respiratory illnesses during the pandemic. The data, provided by the electronic health records network TriNetX, came mainly from the United States, but also included data from Australia, Britain, Spain, Bulgaria, India, Malaysia and Taiwan.
The study group, which included 185,000 children and 242,000 older adults, found that the risks varied by age, with people 65 and older at the greatest risk of lasting neuropsychiatric effects.
For people between the ages of 18 and 64, a particularly significant increased risk was persistent brain fog, affecting 6.4 percent of people who had had Covid compared to 5.5 percent in the control group.
Six months after infection, the children were not found to be at increased risk of mood disorders, although they remained at greater risk of brain fog, insomnia, stroke and epilepsy. None of these effects were permanent for the children. With epilepsy, which is extremely rare, the increased risk was greater.
The study found that 4.5 percent of older people developed dementia in the two years after infection, compared with 3.3 percent of the control group. This 1.2-point increase in a diagnosis as damaging as dementia is particularly concerning, the researchers said.
The study’s reliance on a pool of de-identified electronic health data raised some caveats, especially given the tumultuous timing of the pandemic. Tracking long-term outcomes can be difficult when patients may have sought care through many different health systems, including some outside the TriNetX network.
“I personally find it impossible to judge the validity of data or conclusions when the source of the data is shrouded in mystery and the sources of the data are kept secret by legal agreement,” said Harlan Krumholz, a Yale scientist who has developed an online one. platform where patients can enter their health data.
Taquet said the researchers used several ways to evaluate the data, including making sure it reflected what was already known about the pandemic, such as the drop in death rates during the omicron wave.
Also, said Taquet, “the validity of the data will not be better than the validity of the diagnosis. If clinicians make mistakes, we will make the same mistakes.”
The study follows an earlier study by the same group, which reported last year that a third of Covid patients experienced mood disorders, stroke or dementia six months after infection.
While cautioning that it is impossible to make full comparisons between the effects of recent variants, including omicron and its subvariants, which are currently causing infections, and those that were prevalent a year or more ago, the researchers pointed out some initial findings: Although omicron caused less severe immediate symptoms, long-term neurological and psychiatric outcomes appeared similar to delta waves, indicating that the burden on the world’s health care systems may persist even with less severe variants .
Hannah Davis, a co-founder of the Patient-Led Research Collaborative, which studies Covid-19, said the finding was meaningful. “It goes against the narrative that omicron is milder for long-term Covid, which is not based on science,” Davis said.
“We see this all the time,” Putrino said. “The general conversation continues to leave out Covid for too long. The severity of the initial infection doesn’t matter when we’re talking about long-term consequences that destroy people’s lives.”
Dan Keating contributed to this report.