The honest answer is that we just don’t know how many people have ME/CFS in the UK. We can only make a very rough estimate based on limited epidemiological research, along with the opinion of clinicians, researchers and people who have the condition.
Like most other charities and organisations that deal with ME/CFS we have been using a figure of ‘at least 250,000’ for many years, which dates back to the publication of a 2002 Report to the Chief Medical Officer by an Independent Working Group of which I was a member.
- Prevalence: the percentage of a population that is affected by a specific disease at a particular point in time.
- Population: The UK population was 67.6 million in mid-2022; the latest official estimates (Office for National Statistics).
Report to the Chief Medical Officer by an Independent Working Group on ME/CFS
The report estimated (section 1.4.2 Epidemiology) 0.2 – 0.4% of the population (i.e., that 2 – 4 people in every 1,000) could have ME/CFS. It was Jason et al. in the USA who estimated a prevalence of 0.42% in 1999, which influenced the upper prevalence figure used in the CMO Report:
- Report to the Chief Medical Officer of an Independent Working Group on ME/CFS | January 2002
- Jason et al. A community-based study of chronic fatigue syndrome | October 1999
There are caveats about using the Jason study: i) It appears that the number of people with undiagnosed ME/CFS is higher in the USA than the UK, ii) The study used the ‘Fukuda’ criteria which are less stringent than the 2021 NICE Guideline criteria (or the 2003 Canadian Consensus criteria (revised in 2010)).
The 2002 CMO Working Group highlighted the fact that a reliable measure of prevalence for ME/CFS was missing, and we noted that the organisation of primary care (GP) services in the UK created a unique opportunity to conduct epidemiology studies on a national scale.
However, much of the research evidence that has been published since then is problematic, either from the methodology employed or the diagnostic criteria that is used and could have resulted in either under or overestimates; especially when 10% or more of the population are believed to have ‘chronic fatigue’ that doesn’t relate to ME/CFS.
We know that many people with ME/CFS remain undiagnosed or could have been misdiagnosed. But we don’t know how many have a correct diagnostic entry on their medical records. Despite many parliamentary questions over the years to the Department of Health and Social Care, the NHS has failed to give a proper account.
The UK study upon which the 250,000 figure is also partly based was carried out by Dr Luis Nacul et al. in 2011. It concluded that the minimum prevalence of ME/CFS was 0.2% and it used data from GP practices covering 140,000 patients:
“The estimated minimum prevalence rate of ME/CFS was 0.2% for cases meeting any of the study case definitions, 0.19% for the CDC-1994 definition, 0.11% for the Canadian definition and 0.03% for the ECD. The overall estimated minimal yearly incidence was 0.015%.”
- Nacul et al. Prevalence of ME/CFS in three regions of England: a repeated cross-sectional study in primary care | July 2011
Latest epidemiology
The only new research since then has come from Professor Chris Ponting and Gemma Samms at the University of Edinburgh. This concluded that the prevalence of people with ME/CFS in the UK may be around 390,000 (0.6%), but it also comes with caveats.
“The lifetime prevalence of ME/CFS for English females and males may be as high as 0.92% and 0.25%, respectively, or approximately 390,000 UK individuals overall. This improved estimate of ME/CFS prevalence allows more accurate assessment of the socioeconomic and disease burden imposed by ME/CFS.”
- Preprint: Ponting et al. Unequal access to diagnosis of myalgic encephalomyelitis in England | February 2024
ME/CFS and Long Covid
There has clearly been a rise in the number of people developing post-Covid or Long Covid ME/CFS during the past 4 years, i.e., people whose symptoms match the criteria for ME/CFS. However, the prevalence data remains very speculative.
Two research studies from America estimated that the number of people with Long Covid who meet with ME/CFS diagnostic criteria varied between 40% and 60%. But this cannot be extrapolated to conclude that approximately 50% of almost 2 million people who self-reported as having some form of Long Covid in the UK, might have ME/CFS.
- Office for National Statistics:
- Self-reported coronavirus (COVID-19) infections and associated symptoms, England and Scotland: November 2023 to March 2024.
- Prevalence of ongoing symptoms following coronavirus (COVID-19) infection in the UK: 30 March 2023.
- Research estimating people with Long Covid who meet ME/CFS criteria:
- Bonilla et al. ME/CFS is common in post-acute sequelae of SARS-CoV-2 infection (PASC): Results from a post-COVID-19 multidisciplinary clinic | February 2023
- Jason et al. ME/CFS and Post-Exertional Malaise among Patients with Long COVID | December 2022
We might consider that the number of people with self-reported Long Covid whose ability to ‘undertake everyday activities had been limited a lot’ (i.e., around 380,000 people from ONS data) could potentially meet the diagnostic criteria for ME/CFS.
However, we have no way of knowing if they meet the other criteria e.g., debilitating fatigue, post-exertional malaise, unrefreshing sleep and/or sleep disturbance, and cognitive difficulties (NICE Guideline on ME/CFS). We don’t even have an official diagnostic criterion for Long Covid.
Current situation
The ME Association is reviewing all of this uncertainty and the available evidence on both ME/CFS and Long Covid with a view to updating the estimate that we use, and we are in discussions with other charity colleagues and epidemiologists. We have also commissioned a patient/researcher to prepare a briefing paper on all the available evidence.
A new and comprehensive UK epidemiology study is clearly needed. This sort of research is very expensive to carry out, but we would welcome grant applications to the Ramsay Research Fund and could consider funding a suitable study in combination with another charity or with the Medical Research Council (MRC) or National Institutes of Health Research (NIHR).
Before any decision is made on changing the 250,000 figure we would like to hear from the patient community. If you have a view on epidemiology and the prevalence of ME/CFS, please let us know: Feedback@meassociation.org.uk
While any decision to increase the estimated number of people affected by ME/CFS might have positive implications for future research funding, health and social care provision and for public recognition of ME/CFS, we need to be sure that any new figure can be justified.