One in 20 people in England may have had long COVID, research suggests.
Not everyone who overcomes the coronavirus returns to a clean bill of health.
Regardless of the severity of the infection itself, former coronavirus carriers have reported everything from fatigue to organ damage, despite supposedly clearing the virus from their body.
To better understand the phenomenon's prevalence, scientists from Imperial College London asked more than half a million people in England about their experience of the coronavirus at any point in the pandemic.
Based on the results, which have not yet been published in a peer-reviewed journal, the scientists estimated just under one in five people (19.2%) have had the coronavirus.
More than 76,000 of the study participants claimed to have endured long COVID for at least 12 weeks.
Extrapolating the data out, the scientists have calculated that 5.75% of people – more than 2 million adults in England – have endured at least one long-COVID symptom at some point in the pandemic.
Watch: What is long COVID?
Long COVID's prevalence is somewhat muddled.
A previous estimate suggests more than 1 million people in the UK have endured the condition.
A recent Norwegian study found just over three in five (61%) coronavirus patients have "persistent symptoms" six months later.
Scientists from University College London have also reported that up to 17% of coronavirus carriers endure long COVID for at least 12 weeks.
The Imperial scientists put these varying results down to different long-COVID definitions and study designs.
Long COVID "remains a poorly defined syndrome", they added.
"There is uncertainty about its predisposing factors and the extent of the resultant public health burden, with estimates of prevalence and duration varying widely."
To learn more, the Imperial scientists randomly selected over 508,000 people living in the community.
Between September 2020 and February 2021, the participants were asked if they had endured a suspected or confirmed coronavirus infection at any point in the outbreak.
They were then shown a list of 29 potential long-COVID symptoms – from appetite loss and heavy limbs to diarrhoea and blisters on the feet.
The participants reported if they had experienced any of the symptoms that they attribute to the coronavirus specifically.
Of the over 76,000 study participants who endured long COVID, more than a third (37.7%) experienced one or more complication, while over one in 10 (14.8%) had three or more symptoms.
Based on their results, the scientists have calculated one in 20 (5.75%) people in England have endured at least one long-COVID symptom.
One in 50 (2.22%) people – just under 1 million adults in England – are thought to have had three or more of the lingering symptoms.
Three in 10 (30.5%) of the study participants who endured at least one long-COVID symptom for 12 weeks or more said it had a "significant effect" on their "daily life".
When extrapolated out, one in 100 (1.72%) people in England are expected to have endured a reduced quality of life due to long COVID.
Fatigue was found to be the most common complication, followed by "respiratory and related symptoms".
The scientists stressed, however, that the study participants may have mistakenly attributed any of the 29 symptoms to the coronavirus, causing long COVID's prevalence to be overestimated.
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Overall, women were found to be 51% more likely to endure long COVID. In March 2021, scientists from the University of Leicester reported white women are most at risk of the lingering complications.
Old age, obesity, smoking, vaping, hospitalisation and deprivation were also linked to long COVID.
Perhaps surprisingly, being of Asian ethnicity was associated with a lower risk of the condition. People of a non-white ethnicity are more likely to become seriously ill with the coronavirus itself.
Based on their results, the Imperial scientists believe "clinicians need to be aware of the differing manifestations of long COVID, which may require tailored therapeutic approaches".
Official guidance recommends long-COVID patients set realistic goals and join support forums.
Long COVID's symptoms can be broad, however, with many people calling for each patient to be treated on a case-by-case basis.