The Impact of Pain on Daily Activities in Patients with Idiopathic Inflammatory Myopathies: Report from the OMERACT Myositis Working Group

Background International focus groups with patients with idiopathic inflammatory myopathies (IIM) conducted by the OMERACT Myositis Working Group over the years demonstrated the pain as an important symptom experienced by these patients. In this study, we aimed to examine the frequency and degree of pain interference, the aspects of daily life impacted by pain, and the factors associated with pain interference in adults with IIM. Methods This was a prospective observational study with two visits. The patients who fulfilled the probable/definite IIM (ACR/EULAR Myositis Classification Criteria) were enrolled. Pain interference was assessed with PROMIS pain interference form (6a). Myositis core set measures and PROMIS fatigue (7a) and physical function (8b) were obtained at both visits. Logistic regression and linear mixed models were performed to assess the association between pain interference and other parameters. Results A total of 129 patients with IIM (60% females) were recruited from U.S., South Korea, Netherlands, Sweden, and Australia. Approximately 71% reported pain interference. The patients in the greater pain interference group were more likely to be female, had significantly worse patient/physician global disease activity, fatigue, and physical function than those in the lower pain interference group. The most commonly impacted life aspect was household chores. Manual muscle testing, patient/physician global disease activity, fatigue, and physical function were all significantly associated with pain interference score >60. Conclusion The majority of the patients with IIM experience the impact of pain on their daily activities, particularly household chores. Myositis disease activity, duration, and subtype could be associated with greater pain interference.