Objective: Pain and functional disability are 2 major factors influencing the health status of patients with rheumatoid arthritis (RA). To determine the relative importance ascribed to these factors by patients, we examined the relationship of levels of both pain and functional disability to self-reported global arthritis status in patients with RA.
Methods: Pain, disability and global arthritis status were measured prospectively in 305 patients with RA using the Health Assessment Questionnaire, which was completed by patients every 6 months for up to 9.5 years. The relative importance of pain and functional disability was determined by the relative magnitude of their association with global arthritis status, as estimated by pooled time series regression analysis.
Results: At study entry, median levels of pain, functional disability, and global arthritis status for the cohort were 1.1 (possible range: 0-3.0), 1.25 (possible range: 0-3.0), and 35 (possible range: 0-100), respectively, indicating moderate arthritis severity. Both pain (p < 0.0001) and functional disability (p < 0.0001) were significantly related to changes in global arthritis status over time. The standardized regression coefficient of pain was 1.2 times larger than that of disability, indicating that patients' ratings of their arthritis status was only slightly more heavily weighted by changes in pain than by changes in functional disability. Pain was a more important feature than disability among nonwhites (pain/disability standardized coefficient ratio = 2.7), while disability appeared to be more important for males (ratio = 0.8). The duration of RA did not influence the relative importance of pain and disability.
Conclusion: Pain and functional disability were of similar importance to this group of patients with RA, and the relative importance of pain and disability did not vary with the duration of RA.