Long COVID affects one in eight, says Lancet study

New data indicates that while fatigue, muscle pain and breathing difficulties have risen even in non-infected people over the pandemic, a significantly higher proportion of people with COVID-19 develop persistent Long COVID symptoms.

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What is the research about?

The symptoms of Long COVID can be varied, which has meant that developing a clear definition of who has Long COVID and who is at risk of developing it has been challenging. This is especially the case given that some common symptoms, such as breathing difficulties and fatigue, can also be symptoms of the stress and anxiety that many people have faced during the pandemic.

This study potentially offers a more accurate estimate of how many people develop Long COVID than previous estimates.

To separate out what are truly symptoms of Long COVID, this study in The Lancet set out to compare Long COVID symptoms both between people pre- and post-COVID-19 infection (to look at baseline symptoms before SARS-CoV-2 infection), and also between people who have had COVID-19 and those who have never been infected. This accounts for a potential population increase in symptoms that could be related to the uncertainty and challenges that a global pandemic inevitably brings.

What did the researchers do?

Dutch researchers investigated the frequency of new or severely increased Long COVID-type symptoms across an uninfected population and compared them with these symptoms in people who have been diagnosed with COVID-19. This was to provide a more reliable estimate for the prevalence of Long COVID than in previous studies. They did this by sending out 24 surveys between March 2020 and August 2021 to record whether people had been diagnosed with COVID-19, had developed any symptoms, or seen existing symptoms exacerbated .

What did they find?

The core symptoms recorded included chest pain, difficulties or pain when breathing, painful muscles, fatigue, loss of taste or smell and tingling hands or feet.

Of 76,422 participants, there were 4,231 (5.5%) who had COVID-19 and 8,462 control participants who had not been infected. Of people who had COVID-19, 21.4% experienced at least one new or severely increased symptom three to five months post-infection compared to before infection. By comparison in the control group, only 8.7% of uninfected people who were followed in the same time period saw symptoms emerge or increase.

Assuming that 8.7% of infected people could also have had some increase in symptoms over the pandemic, this indicates that the remaining 12.7% (one in eight) had long-term symptoms directly related to their COVID-19 infection.

What does this mean?

This study potentially offers a more accurate estimate of how many people develop Long COVID than previous estimates as it takes into account both existing symptoms and also “symptoms which may have been a result of non-infectious disease health aspects of the pandemic, such as stress caused by restrictions and uncertainty”.

As critical as the study is, the researchers note a few gaps – one being that they did not include mental health symptoms (for example depression and anxiety symptoms), along with brain fog, insomnia, and post-exertional malaise, which have frequently been cited as important Long COVID symptoms, but that these need to be investigated in the future.

They also were unable to study the causes of Long COVID symptoms, which also requires more research into the mechanisms behind them. Finally, as the data was collected before COVID-19 vaccine rollout in the Netherlands was completed, they were unable to assess the effect of vaccination nor of different SARS-CoV-2 variants on Long COVID symptoms.