Incidence, Prevalence, and Predictors of Fibromyalgia in People with Inflammatory Arthritis: An Observational Cohort Study using the Clinical Practice Research Datalink Aurum.

Study type
Protocol
Date of Approval
Study reference ID
23_003588
Lay Summary

Inflammatory arthritis includes several different conditions causing inflamed joints. The commonest types are “rheumatoid arthritis”, “psoriatic arthritis”, and “axial spondyloarthritis”. It is common, affecting 1 in 100 people.

Persistent pain is common in people with inflammatory arthritis. Whilst it has many causes, previous studies have shown it is often related to the development of a condition called “fibromyalgia”. Fibromyalgia is thought to result from abnormal levels of certain chemicals in the body’s nerves. It changes how people experience pain and other sensations, leading to pain throughout the body, fatigue, and foggy thinking. Fibromyalgia affects 2 in 100 people but is estimated to affect up to 21 in 100 people with inflammatory arthritis.

Very few studies have looked at when fibromyalgia occurs in people with inflammatory arthritis or whether some people with inflammatory arthritis are more likely to develop it. Understanding this is important as knowing when fibromyalgia happens in people with inflammatory arthritis and who is most likely to develop it could allow timely treatment to be used to reduce its impacts on patients’ lives. It could also support further research exploring why fibromyalgia is much commoner in people with inflammatory arthritis and whether it can be prevented.

Our study will investigate when and how often fibromyalgia occurs in people with inflammatory arthritis in the Clinical Practice Research Datalink Aurum database. It will also explore whether there are certain characteristics that people with inflammatory arthritis have when they are diagnosed with arthritis that make them more likely to develop fibromyalgia.

Technical Summary

Fibromyalgia, a chronic condition characterised by widespread nociplastic pain alongside somatic, cognitive and mood symptoms, has been shown to affect approximately 1.8% of the general population. However, among people with inflammatory arthritis – an umbrella-term referring to conditions associated with inflammation of the joints and surrounding soft tissues – the prevalence is significantly higher with a recent meta-analysis reporting it to affect 21%, 18% and 13% of people with rheumatoid arthritis, psoriatic arthritis and axial spondyloarthropathy, respectively. Fibromyalgia not only disproportionately affects people with inflammatory arthritis but has been shown to worsen disease outcomes and increase healthcare utilisation as well as result in higher levels of work-related disability.

Few longitudinal studies have examined when fibromyalgia occurs in people with inflammatory arthritis. These are limited by small sample sizes, short follow-up durations (with no study examining fibromyalgia incidence across the entire disease course), and a lack of information about how this varies across inflammatory arthritis subtypes and by socioeconomic factors such as age, gender, and deprivation. There is also little published information on prognostic factors that are associated with the subsequent development of fibromyalgia in people with inflammatory arthritis.

We will describe the annual incidence of fibromyalgia, its prevalence at various time points in the arthritis disease course and in different sociodemographic groups. Values will be presented as proportions with confidence intervals. We will examine prognostic factors for the subsequent development of fibromyalgia present at arthritis diagnosis using Kaplan-Meir plots with accompanying Cox proportional hazards regression models.

Our findings will provide valuable insight into when fibromyalgia occurs in people with inflammatory arthritis and which groups of people are most at risk of its development, supporting the design of healthcare approaches to reduce the impacts of pain from fibromyalgia in people with inflammatory arthritis and informing future research studies into its course.

Health Outcomes to be Measured

SNOMED/Read code for a diagnosis of fibromyalgia.

Collaborators

Ian Scott - Chief Investigator - Keele University
Kolawole Adeniran - Corresponding Applicant - Keele University
Christian Mallen - Collaborator - Keele University
James Bailey - Collaborator - Keele University
Richard Partington - Collaborator - Keele University
Sara Muller - Collaborator - Keele University

Linkages

Patient Level Index of Multiple Deprivation