Recent research in myalgic encephalomyelitis / chronic fatigue syndrome: an evidence map

Alex Todhunter-Brown*, Pauline Campbell, Cathryn Broderick, Julie Cowie, Bridget Davis, Candida Fenton, Sarah Markham, Ceri Sellers, Katie Thomson

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

Myalgic encephalomyelitis / chronic fatigue syndrome (ME/CFS) is a chronic condition, classified by WHO as a nervous system disease, impacting around 17 million people worldwide. Presentation involves persistent fatigue and post-exertional malaise (PEM; a worsening of symptoms after minimal exertion) and a wide range of other symptoms. Case definitions have historically varied; PEM is a core diagnostic criterion in current definitions. In 2022, a James Lind Alliance Priority Setting Partnership (JLAPSP) established research priorities relating to ME/CFS.

Objective(s)

We created a map of ME/CFS evidence (2018-2023), showing the volume and key
characteristics of recent research in this field. We considered diagnostic criteria and how current research maps against the JLAPSP research priorities.

Methods

Using a pre-defined protocol, we conducted a comprehensive search of Cochrane, MEDLINE, Embase and CINAHL. We included all English-language research studies published between January 2018 and May 2023. Two reviewers independently applied inclusion criteria with consensus involving additional reviewers. Studies including people diagnosed with ME/CFS using any criteria (including self-report), of any age and in any setting were eligible. Studies with < 10 ME/CFS participants were excluded. Data extraction, coding of topics (involving stakeholder consultation) and methodological quality assessment of systematic reviews (using AMSTAR2) was conducted independently by
two reviewers, with disagreements resolved by a third reviewer. Studies were presented in an evidence map.

Results

Of 11,278 identified studies, 742 met the selection criteria but only 639 provided sufficient data for inclusion in the evidence map. These reported data from approximately 610,000 people with ME/CFS. There were 81 systematic reviews, 72 experimental studies, 423 observational studies and 63 studies with other designs. Most studies (94%) were from highincome countries. Reporting of participant details was poor; 16% did not report gender, 74% did not report ethnicity and 81% did not report severity of ME/CFS. Forty-four percent of
studies used multiple diagnostic criteria, 16% did not specify criteria, 24% used a single criteria not requiring PEM and 10% used a single criteria requiring PEM. Most (89%) systematic reviews had low methodological quality. Five main topics (37 subtopics) were included in the evidence map. Of the 639 studies; 53%
addressed the topic ‘what is the cause?’; 38% ‘what is the problem?’; 26% ‘what can we do about it?’; 15% ‘diagnosis and assessment’; and 13% other topics, including ‘living with ME/CFS’.

Discussion

Studies have been presented in an interactive evidence map according to topic, study design, diagnostic criteria and age. This evidence map should inform decisions about future ME/CFS research.

Limitations

An evidence map does not summarise what the evidence says. Our evidence map only includes studies published in 2018 or later and in English language. Inconsistent reporting and use of diagnostic criteria limits interpretation of evidence. We assessed methodological quality of systematic reviews, but not of primary studies.

Conclusions

We have produced an interactive evidence map, summarising ME/CFS research from 2018- 2023. This evidence map can inform strategic plans for future research. We found some, often limited, evidence addressing every JLAPSP priority; high-quality systematic reviews should inform future studies.
Original languageEnglish
JournalNIHR Journals Library
Publication statusAccepted/In press - 19 Dec 2024

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