Review articleFunctional somatic syndromes and joint hypermobility: A systematic review and meta-analysis
Introduction
The functional somatic syndromes (FSS) are a group of chronic disorders with a range of largely somatic syndromes that lack an accepted organic cause [1]. Notable examples are fibromyalgia, chronic fatigue syndrome (CFS) and irritable bowel syndrome [[1], [2], [3], [4]]. Though these conditions span different body systems, they share several features – i) their causes are uncertain and believed to be multifactorial [5], one factor being the psychological; ii) they are more common in young females [1,4]; iii) they have overlapping signs and symptoms [4] and iv) they have similarities with regards to the therapies to which they respond [4]. These common features have led some to argue that FSS may be manifestations of the same disease in different organ systems [4].
The aetiology of FSS constitute a significant gap in current medical knowledge. Despite high prevalence and involving significant deterioration in function and quality of life [4], FSSs pose substantial difficulties in accurate diagnosis and effective treatment [4,6,7]. A rational approach to developing better therapies for FSSs should begin with understanding their underlying causes. Hypermobile joints are one possible aetiological factor in FSS, either directly or, perhaps more likely, by the underlying connective tissue disorder which causes the hypermobility.
Joint hypermobility (JH) is a connective tissue phenotype characterised by joint laxity with an increased range of joint movement [8]. One common scale for assessing JH, for example, the Beighton criteria, assesses passive dorsiflexion of the little fingers beyond 90°, passive apposition of the thumbs to the flexor aspects of the forearm, hyperextension of the elbows to beyond 10°, hyperextension of the knees to beyond 10°, and forward flexion of the trunk with knees fully extended so that the palms of the hands rest flat on the floor, with 4 or more items (measuring each limb separately) indicating JH [9]. JH is the common feature of heritable connective tissue disorders including benign joint hypermobility syndrome (JHS), Marfan syndrome and Ehlers-Danlos syndrome [8]. However, asymptomatic JH in the absence of other connective tissue disorders is benign and not uncommon in the general population, with a higher prevalence in females, younger age groups and certain ethnicities (Asian, African) [8,10].
In recent decades, an association has been noted between JH and various FSSs [[11], [12], [13]]. The relevance of these findings is yet to be fully elucidated. Despite the associations being first reported more than 20 years ago [14], there have been no systematic reviews published to date. Here we reviewed the relevant literature for studies containing primary data describing the relationship between JH and these specific conditions.
Section snippets
Search strategy
A systematic search of the databases Medline and PsycINFO was conducted on the 3rd of March 2020 to identify all studies from inception to February 2020. The search included MeSH terms, key words, Boolean operators (‘AND’ and ‘OR’) and truncations (*). MeSH terms were used wherever possible and complemented with specific key words to capture synonyms, spelling and suffix variations, and abbreviations.
FSSs sought were fibromyalgia, chronic fatigue syndrome, tension-type headache,
Results
We found 220 studies, which after exclusions yielded 11 studies for inclusion. There were 5 studies on fibromyalgia, 3 studies on CFS and 3 studies on FGID.
Key features of each study, including sample size, results of the study and overall quality rating are summarised in Table 1. Quality ratings (i.e. ‘Good’, ‘Fair’ and ‘Poor’) were assessed using the Newcastle-Ottowa Scale for observational studies [19] and its associated scoring algorithm, which can be found in Table A1, Table A2 within the
Meta-analysis
With the exception of Inayet et al., all studies included in the qualitative review were also included in the meta-analysis. The Inayet study was excluded for not reporting proportions of diagnosis of FSS and for studying FSS among JH as opposed to JH among FSS. A random-effects meta-analysis of odds ratio combining the remaining ten studies – 5 on fibromyalgia, 3 on CFS and 2 on FGID, found the weighted odds ratio (i.e. summary effect size) to be 3.27 (95% CI: 1.83, 5.84; p < 0.001),
Discussion
We reviewed eleven studies, nine of which showed an association of hypermobility with three different FSSs – fibromyalgia, CFS and FGID. The studies mostly had large numbers of participants and used similar diagnostic criteria. However, they were generally of fair to poor quality and two studies recruited children and one study recruited adolescents.
These findings are significant for a few reasons. The association between JH and FSSs lacks an explanation. Unfortunately, this review does not
Conclusion
Data indicates that there is an association between functional somatic syndromes and joint hypermobility. However, the evidence is limited by the generally low quality of studies, narrow range of functional somatic syndromes studied and the risk of publication bias. Better research is needed to confirm these findings, as well as evaluate causation using prospective cohort studies.
Fund
No funding was received.
Declaration of Competing Interest
No conflicts of interest to declare.
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