Factors influencing fibromyalgia in patients with axial spondyloarthritis
What was the background to this study?
Fibromyalgia is a chronic disease where the main symptom is generalised musculoskeletal pain. Fibromyalgia can frequently occur in patients with axial spondyloarthritis (axSpa), a rheumatic disease with inflammation and stiffness in the spine.
In this study we examined change in fibromyalgia over a one-year period in patients with axSpa. Specifically, we sought to identify factors that can predict who will develop fibromyalgia and who will recover. Fibromyalgia was diagnosed using a self-reported questionnaire.
What did we find?
We used data from 801 patients who have been included in the British Society of Rheumatology Biologics Register for patients with Ankylosing Spondylitis (BSRBR-AS). Information in the register was recorded at two separate times for each person; once when they joined the register (also called the ‘baseline’ measurement), and again after one year.
We divided patients into two groups according to whether they had fibromyalgia or not when they were first included in the study. 86% (686) of patients did not have fibromyalgia at baseline, but 7% (45) in this group developed the condition during the one-year observation period. Of the remaining 14% (115) of the patients who had fibromyalgia at baseline, only 33% (38) still fulfilled the diagnostic criteria for fibromyalgia after one year. Those patients who had developed fibromyalgia more severe axSpa symptoms at baseline, and more generalised pain. The patients who recovered from fibromyalgia, on the other hand, tended to be those with less severe axSpa symptoms and less generalised pain at baseline, and were more likely to have started on biologics medication during the follow-up period.
What does this mean?
The findings of this study seem to suggest that:
A considerable proportion of patients who have both axial spondyloarthritis and fibromyalgia will recover from the fibromyalgia during the course of a year.
Of those with axSpa but no fibromyalgia, a small proportion of patients will go on to develop fibromyalgia in the same period.
We have identified some factors which can predict who will recover from or develop fibromyalgia, but we have still not found what causes the disease to develop in these patients.
