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New data reveals how many people scientists suspect have long COVID

The study asked over 75,000 people about the 23 symptoms most commonly associated with long COVID.

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By Danny Halpin via SWNS

One in eight people develop long COVID after being infected with the coronavirus, a new study has shown.

It is the first research to measure long-term symptoms in both infected and non-infected people and therefore creates a more accurate distinction between symptoms caused by long COVID and those from other reasons such as stress or insomnia.

Professor Judith Rosmalen from the University of Groningen and lead author of the study said: “There is an urgent need for data informing the scale and scope of the long-term symptoms experienced by some patients after COVID-19 illness.

“However, most previous research into long COVID has not looked at the frequency of these symptoms in people who haven’t been diagnosed with COVID-19 or looked at individual patients’ symptoms before the diagnosis of COVID-19.

“Our study approach looks at the symptoms most often associated with long COVID, including breathing problems, fatigue and loss of taste and/or smell, both before COVID-19 diagnosis and in people who have not been diagnosed with COVID-19.

“This method allows us to take pre-existing symptoms and symptoms in non-infected people into account to offer an improved working definition for long COVID and provide a reliable estimate at how likely long COVID-19 is to occur in the general population.”

The study, carried out by Dutch researchers and published in The Lancet, asked 76,422 people in the Netherlands to fill out a digital questionnaire on the 23 symptoms most commonly associated with long COVID.

Questionnaires were sent to each participant 24 times between March 2020 and August 2021. The survey therefore only included those infected with the alpha or earlier variants.

Also, the survey was conducted before the vaccine rollout in the Netherlands and so did not study vaccinated people.

Everyone who tested positive (4,231) was matched with two people who didn’t (8,462), in order to create a control group and take into account variations in sex, age, and the time it took to complete the questionnaire.

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Researchers found several core symptoms that were new or more severe three to five months after becoming infected – chest pain, difficulties breathing, pain when breathing, painful muscles, loss of taste and/or smell, tingling hands/feet, a lump in the throat, alternately feeling hot and cold, heavy arms and/or legs and general tiredness.

Ph.D. candidate and first author of the study, Aranka Ballering said: “These core symptoms have major implications for future research, as these symptoms can be used to distinguish between post-COVID-19 condition and non-COVID-19-related symptoms.”

Of the participants who had sent in pre-COVID symptom data, the researchers found that 21.4 percent of those who tested positive, and 8.7 percent of those who didn’t, experienced at least one core symptom that became moderately severe.

That implies that for 12.7 percent of COVID-19 patients their new symptoms can be attributed to the virus.

Ballering added: “By looking at symptoms in an uninfected control group and in individuals both before and after SARS-CoV-2 infection, we were able to account for symptoms which may have been a result of non-infectious disease health aspects of the pandemic, such as stress caused by restrictions and uncertainty.

“Post-COVID-19 condition, otherwise known as long COVID, is an urgent problem with a mounting human toll.

“Understanding the core symptoms and the prevalence of post-COVID-19 in the general population represents a major step forward for our ability to design studies that can ultimately inform successful healthcare responses to the long-term symptoms of COVID-19.”

The authors acknowledged limitations to the study, in that it does not include data from the delta or omicron variants which caused the most infections and, due to asymptomatic infection, some positive cases of COVID may have gone unreported.

They also recognized that other symptoms like brain fog have since been identified as potentially relevant for a definition of long COVID that were not included in the study.

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Also, the participants were all from one region and therefore not ethnically diverse.

Professor Rosmalen said: “Future research should include mental health symptoms (e.g. depression and anxiety symptoms), along with additional post-infectious symptoms that we could not assess in this study (such as brain fog, insomnia, and post-exertional malaise).

“We were unable to investigate what might cause any of the symptoms observed after COVID-19 in this study, but we hope future research will be able to give insights into the mechanisms involved.

“Furthermore, due to the timing of this study, we were unable to assess the effect of COVID-19 vaccination and different SARS-CoV-2 variants on long COVID symptoms.

"We hope future studies will provide answers on the impacts of these factors.”

Writing in a linked comment, Professor Christopher Brightling and Dr. Rachael Evans of the University of Leicester, who were not involved in the study, said: “This is a major advance on prior long COVID prevalence estimates as it includes a matched uninfected group and accounts for symptoms before COVID-19 infection.

“The pattern of symptomatology observed by Ballering and colleagues was similar to previous reports with fatigue and breathlessness amongst the commonest symptoms, but interestingly other symptoms such as chest pain were more a feature in those with long COVID versus uninfected controls.

“Current evidence supports the view that long COVID is common and can persist for at least two years, although severe debilitating disease is present in a minority.

“The long COVID case definition needs to be further improved, potentially to describe different types of long COVID, for which better mechanistic understanding is critical.”

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