ONE in eight adults suffer long Covid symptoms following infection, according to a Dutch study which provides the most reliable estimates for the condition to date.
Researchers in the Netherlands tracked more than 76,000 participants who were asked regularly fill out digital questionnaires on 23 symptoms commonly associated with long Covid.
The questionnaire was sent out 24 times to the same individuals between March 2020 and August 2021.
Over the course of the study, 4,231 participants had a positive Covid test and were matched against a control group of 8,462 participants matched for age and sex.
The time period of the study meant that Covid infections would have been caused by the Alpha or earlier variants, and pre-dated the vaccine rollout.
Covid vaccination has been found to reduce the risk of Long Covid, and the Omicron variant appears less likely than Delta to lead to Long Covid.
The researchers found that several "core" symptoms were new or more severe three to five months after having Covid-19, compared to before a Covid-19 diagnosis and to the uninfected control group.
These were: chest pain, difficulties breathing, pain when breathing, painful muscles, loss of taste and/or smell, tingling hands/feet, a lump in throat, alternately feeling hot and cold, heavy arms and/or legs and general tiredness.
The severity of these symptoms plateaued at three months after infection with no further decline.
The findings are published in the Lancet.
Lead author of the study, Professor Judith Rosmalen, from the University of Groningen, said: “There is 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 a 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.”
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Aranka Ballering, a PhD candidate and first author on the study, added: “By looking at symptoms in an uninfected control group and in individuals both before and after [Covid] 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.”
Their analysis found that 12.7% of people who caught Covid would still be experiencing symptoms caused by the infection three months later.
However, the authors cautioned that the study predated Omicron and that asymptomatic infections may have been missed.
Writing in a linked comment article, Professor Christopher Brightling and Dr Rachael Evans of the Institute for Lung Health, University of Leicester (who were not involved in the study), state: “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."
It comes as figures for Scotland show that 57,000 Scots have been living with Long Covid for more than 12 months, with 75% saying that the symptoms affect their day-to-day activities.
The estimates from the Office for National Statistics, which are based on self-reported Long Covid, suggest that 164,000 people in total in Scotland are living with the condition (of any duration).
Allan Cowie, interim chief executive at Chest Heart & Stroke Scotland, said: “Tens of thousands of people in Scotland have been living with the effects of Long Covid for well over a year now and their daily lives are being hugely impacted by debilitating symptoms.
“People living with the condition tell us that Long Covid is affecting their ability to work, socialise with friends and family, exercise and even leave the house. On top of that they are still struggling to access the tests they need and support isn’t consistent.
"There needs to be a full wraparound package of care in place that caters to people’s medical needs and provides holistic support to help them live well with their condition."