Background/Purpose: Fibromyalgia is often associated with various comorbid conditions. A high prevalence of fibromyalgia in patients with rheumatic diseases has been reported. Previous studies showed that patients with rheumatoid arthritis (RA) and fibromyalgia had worse RA symptoms, greater disease activity, and worse physical and mental quality of life (QOL) compared with patients who have RA without fibromyalgia. How a comorbidity of rheumatic disease affects symptom severity, QOL, and treatment outcome in patients with fibromyalgia is unknown. This study aims to evaluate the association of rheumatic diseases with symptom severity, QOL, and treatment outcome in patients with fibromyalgia.

Methods: The initial study population consisted of 978 patients who were confirmed to have fibromyalgia and completed the brief multidisciplinary fibromyalgia treatment program (FTP), with emphasis on cognitive behavioral therapy (CBT). We based the present analysis on the 536 patients who returned survey questionnaires during the 6- to 12-month follow-up period (mean follow-up duration was 11.7 months; overall survey response rate, 54.8%). The Fibromyalgia Impact Questionnaire (FIQ) and the Short Form-36 Health Status Questionnaire (SF-36) were completed at initial evaluation and at 6- to 12-months follow-up period. Information about the presence or absence of inflammatory rheumatic disease (IRD) of each participant at initial evaluation in the FTP was collected retrospectively from the electronic medical record by an investigator. Presence of IRD was determined by physician diagnosis. Two-sample t test and multivariate regression analyses were performed to compare the rheumatic and nonrheumatic groups.

Results: Thirty-six patients (6.7%) had documented IRDs, with undifferentiated inflammatory arthritis and rheumatoid arthritis being the common IRDs. At baseline, the rheumatic group had poorer scores in SF-36 physical functioning (P=.02), pain index (P=.01), and physical component summary (P=.009) than the nonrheumatic group. After the FTP, both groups tended to improve; however, the rheumatic group had significantly less improvement in the FIQ subscales in pain (P=.02) and work missed days (P=.02), and in the SF-36 physical functioning (P=.02) compared to the nonrheumatic group.

Conclusion: Our findings suggest that IRD is a relatively common comorbidity among patients with fibromyalgia, with a prevalence of about 7% in the study population. Fibromyalgia patients with IRDs have worse SF-36–assessed physical health and pain but not for mental health at baseline compared to fibromyalgia patients without rheumatic diseases. In addition, the rheumatic group demonstrated lower treatment response to the FTP compared to the nonrheumatic group. Our study suggests that our brief FTP based on CBT is less efficacious in patients with fibromyalgia who have IRDs than in those who do not have IRDs. Further studies that seek to identify the relations and the pathophysiologic mechanisms linking fibromyalgia and IRDs will likely advance the understanding of these overlapping chronic conditions.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/association-of-rheumatic-diseases-with-symptom-severity-quality-of-life-and-treatment-outcome-in-patients-with-fibromyalgia/