Fibromyalgia and the Prediction of Two‐Year Changes in Functional Status in Rheumatoid Arthritis Patients

Objective Previous cross‐sectional studies have shown that rheumatoid arthritis ( RA ) patients with fibromyalgia ( FM ) have higher disease activity, greater medical costs, and worse quality of life compared to RA patients without FM . We determined the impact of FM on 2‐year changes in the functional status of RA patients in a prospective study. Methods Subjects included participants in the Brigham Rheumatoid Arthritis Sequential Study who were enrolled in a substudy of the effects of pain in RA . Subjects completed questionnaires, including the Multi‐Dimensional Health Assessment Questionnaire ( MDHAQ ) and Polysymptomatic Distress ( PSD ) scale, semiannually, and underwent physical examination and laboratory tests yearly. Results Of the 156 included RA subjects, 16.7% had FM , while 83.3% did not. In a multivariable linear regression model adjusted for age, sex, race, baseline MDHAQ score, disease duration, rheumatoid factor/cyclic citrullinated peptide antibody seropositivity, disease activity, and psychological distress, RA patients with FM had a 0.14 greater 2‐year increase in MDHAQ score than RA patients without FM ( P = 0.021). In secondary analyses examining the association between continuous PSD scale score and change in MDHAQ , higher PSD scale scores were significantly associated with greater 2‐year increases in MDHAQ score (β coefficient 0.013, P = 0.011). Conclusion Both the presence of FM and increasing number of FM symptoms predicted worsening of functional status among individuals with RA . Among individuals with RA and FM , the magnitude of the difference in changes in MDHAQ was 4‐ to 7‐fold higher than typical changes in MDHAQ score among individuals with established RA .