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Long COVID -- defined as one or more clusters of symptoms lasting 3 months or longer -- occurred in about 6% of people with symptomatic SARS-CoV-2 infection, a modeling study based on 1.2 million global COVID patients showed.

After adjusting for pre-COVID health status, an estimated 6.2% (95% uncertainty interval [UI] 2.4-13.3) of people with symptomatic infection experienced at least one of three long COVID symptom clusters in 2020 and 2021, according to Theo Vos, PhD, of the University of Washington in Seattle, and colleagues from the Global Burden of Disease Long COVID Collaborators group in .

This included:

• 2.2% (95% UI 0.3-7.6) who had cognitive problems
• 3.2% (95% UI 0.6-10.0) who had persistent fatigue with bodily pain or mood swings
• 3.7% (95% UI 0.9-9.6) who had ongoing respiratory problems

In people ages 20 and older, long COVID symptom clusters were more common in women (10.6%, 95% UI 4.3-22.2) than men (5.4%, 95% UI 2.2-11.7). For those under age 20, long COVID affected 2.8% (95% UI 0.9-7.0) of symptomatic COVID patients of both sexes.

Estimated symptom duration was 9 months (95% UI 7.0-12.0 months) for hospitalized COVID patients and 4 months (95% UI 3.6-4.6 months) for those who weren't hospitalized. By the 1-year mark, 15.1% of all those with long COVID still had symptoms.

The global analysis involved Bayesian meta-regression and pooling of 54 studies and two medical record databases, incorporating data for 1.2 million people with symptomatic SARS-CoV-2 infection from 22 countries.

"We synthesized available knowledge on the occurrence, severity, and duration of three common symptom clusters of long COVID," Vos told 名媛直播.

"Importantly, we anchored our estimates on the difference between those who experienced a SARS-CoV-2 infection and those who did not, or by comparing people rating symptoms before and after they had COVID-19," Vos explained.

"As all these symptoms are common, not correcting would lead to overestimation," he added. "Worse so -- as some people do -- is when you count any of many symptoms as defining long COVID and do not correct for their occurrence in those not having been infected."

"We have not covered the full spectrum of long COVID symptoms," Vos acknowledged. And the symptom severity for some patients was substantial -- "on the order of what we measure for people with deafness or long-term consequences of more severe traumatic brain injury," he noted.

"An analysis of the largest contributing cohort with most detailed information suggested that, among those reporting not having recovered and worse off in terms of general health, we largely missed people reporting similar symptoms at a lesser severity level," he said. "It means we are undercounting."

Of the 54 studies included in the analysis, 44 were published and 10 were collaborating cohort studies in Austria, the Faroe Islands, Germany, Iran, Italy, the Netherlands, Russia, Sweden, Switzerland, and the U.S. Published studies included 10,501 hospitalized and 42,891 non-hospitalized COVID patients. Cohort studies included 10,526 hospitalized and 1,906 non-hospitalized patients.

In addition, data from two U.S. electronic medical record databases -- spanning 250,928 hospitalized and 846,046 non-hospitalized patients -- were used. Data collection was from March 2020 to January 2022 and did not cover the Omicron variant wave.

The analyses were based on the World Health Organization clinical case . Symptoms were new-onset and persisted for 3 months after symptomatic SARS-CoV-2 infection.

The estimated proportion of people with at least one of the three long COVID symptom clusters was greater in patients admitted to ICUs (43.1%, 95% UI 22.6-65.2) or general hospital wards (27.5%, 95% UI 12.1-47.8) than among people not hospitalized (5.7%, 95% UI 1.9-13.1).

In more than a third (38.4%) of all long COVID cases, two or all three of the symptom clusters overlapped.

The analysis had several limitations, Vos and colleagues noted. "The 95% UIs around the estimates are wide, reflecting limited and heterogeneous data," they wrote.

Algorithms had to be formulated for each study to achieve cluster definition consistency. The researchers also assumed long COVID followed a similar course in all geographic locations.

"While we estimate that the majority of cases recover within a year, it still leaves many persons with ongoing symptoms," Vos noted. "The information is not yet there to determine the course of their symptoms beyond 1 year."

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