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NIHR publishes second themed review on ‘Long Covid’

Published: 16 March 2021

The NIHR Centre for Engagement and Dissemination (NIHR) has today published its second themed review into ‘Long Covid’.

Building upon its first themed review published in October 2020, the second review considered over 300 papers and academic opinion pieces from across the world, and provides a unique, evidence-based perspective.

The review finds that there is a considerable variation in the range of symptoms that have been considered Long Covid by researchers. Used as an umbrella term, Long Covid may cover conditions which may have different causes.

This lack of consistency around the definition and measurement of Long Covid makes it difficult to synthesise all the different emerging results, and also continues to hinder clinical consensus on what Long Covid actually is.

Nevertheless, after assessing the most recent available evidence, the review supports the possibility, highlighted in its first iteration, that there may be grounds to understand Long Covid as up to four syndromes, with different underlying causes and treatment needs.

These syndromes could include post-ICU syndrome; long-term organ damage; post-viral syndrome and, potentially, an entirely novel syndrome, separate from the others such that it could more specifically and uniquely be identified as ‘Long Covid’. Indeed there is some recent evidence that Long Covid might be an active disease, with continued inflammatory responses, lingering viral activity and/or blood clotting disorders.

Research considered in the review also suggests that:

  • For those admitted to hospital, between 50-89% had at least one enduring symptom after two months. Of those not admitted to hospital, 20-30% experience at least one enduring symptom around one month later and at least 10% three months later;
  • Long Covid appears to be more prevalent in women and in young people (including children) than might have been expected from acute Covid19 mortality;
  • There is increased evidence of organ impairment in both people who were admitted to hospital and those who stayed at home;
  • In one study it was found that 30% of people suffered from anxiety and/or depression between 1-3 months after clearance of the virus. More data is needed on this issue;
  • There is some indication that ‘brain fog’ - one of the recurring pattern of symptoms relating to Long Covid - has a neurological rather than a social cause.

Dr. Elaine Maxwell, review author and Content Lead at the NIHR Centre for Engagement and Dissemination said:

“While this review goes some way to improving our understanding of different patterns of the disease, we need to know more about the prevalence of each and their causes. We also need more data on how long symptoms last.

“It appears that at least 10% of people are experiencing at least one Long Covid symptom three months after diagnosis, but limitations in the way data is collected means this may not be a comprehensive reflection and we may see estimates increase”.

Professor Chris Whitty, Chief Medical Officer and co-lead for the NIHR, said:

“This is a useful review of evidence currently available on the prolonged post-COVID symptoms currently termed ‘Long Covid’ which is highly debilitating for some of those who have had COVID.

“”What we currently term ‘Long Covid’ likely covers a range of syndromes, which will require different approaches. It is important that we work out what exactly the various elements of ‘Long Covid’ are and then we can target research at these parts in order to prevent and treat it.”

Candace Imison, Associate Director of Evidence and Dissemination at the NIHR Centre for Engagement and Dissemination (CED) said:

“Like so much else relating to Covid-19, ‘Long Covid’ has quickly become part of our everyday language, yet so much about it is unknown - though research commissioned by NIHR and others is urgently being done to find out more.

“This second review takes us on from our first by focusing on a wide range of emerging evidence that simply didn’t exist even six months ago. Together with findings from our short survey for people living with Long Covid, it provides a unique insight into the current state of play.

“Through our themed reviews, we aim to act as knowledge brokers, working collaboratively with the public and experts to improve health and social care and inform policy and future research priorities. We hope this review will also be helpful for professionals, who are increasingly coming into contact with people with Long Covid, and for people experiencing enduring symptoms from Covid-19 as well as their families or employers.”

NIHR survey - a complement to the evidence

In addition to the review of the published information, the NIHR launched a short survey for people living with Long Covid, which attracted over 3,000 responses and serves as an additional barometer to complement the emerging scientific evidence.

In common with many other surveys on Long Covid, this is a self-selected sample, and so may not be generalisable to the whole population.

From the NIHR’s survey of 3,286 people with Long Covid conducted following the first review, we found that:

  • 71% of respondents said Long Covid was affecting family life;
  • 39% said it was impacting their ability to care for dependents;
  • 80% said Long Covid affected their ability to work;
  • 36% said it was affecting their finances;
  • 23% wanted a caseworker to coordinate care;
  • 15% had not sought any access to healthcare services, 85% had;
  • 32% had not been able to access all of the healthcare services they thought they needed;

Recommendations from the review and survey

On the combined findings of the thematic review and the survey, Dr Elaine Maxwell said:

“It is clear that although there are interesting studies happening around the world, more research is needed on the incidence of Long Covid and its causes. This will help to predict and prevent Long Covid in the longer term. In particular, there is an urgent need to research treatments and management for people with the condition.

“Management of Long Covid has so far focused on ruling out other diagnoses, treating individual symptoms and rehabilitation, and access to services has been variable. Looking forward, we need to offer a holistic, integrated approach rather than symptom by symptom management. We recommend rapid evaluation of different service models and skill mix for supporting people with Long Covid.”

Other conclusions and recommendations for future research and support of people with Long Covid are as follows:

  • Targeted research to better understand the disease patterns and symptom clusters that currently sit under the umbrella of Long Covid or post Covid
  • Some elements of Long Covid are similar to other conditions and evaluations of interventions (pharmaceutical, psychological and physical therapies) that may improve symptoms are needed. We recommend evaluation of the use of interventions that have been effective in other conditions when used with people with Long Covid. For non-pharmaceutical interventions, a range of research methodologies should be encouraged.
  • Seldom heard voices are not visible in the current evidence. We recommend research that is targeted at vulnerable people (including older people and people with Learning Disabilities) as well as hard to reach groups including travellers and prison populations.
  • We recommend that people living with Long Covid (who are experts by experience) should be equal partners in setting the research agenda.

Themed reviews are not systematic reviews of all published evidence. This review considered 302 international publications (including pre-prints and opinion pieces) and narrowed this down to address key themes, so papers were included based on how they added to the narrative.

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