Objective: To examine the degree to which disease severity and domains of self-efficacy (pain, function, and other symptoms) explain pain and functioning in rheumatoid arthritis (RA) patients.
Methods: Patients (n = 263) completed the Arthritis Impact Measurement Scales 2 to assess pain and functioning (physical, affective, and social), the Arthritis Self-Efficacy Scale to assess 3 self-efficacy domains (pain, physical function, and other). Disease severity was assessed with C-reactive protein level, physician's rating, and abnormal joint count. Structural equation modeling was used to examine 3 hypotheses: does disease severity have a direct relationship with pain and each area of functioning, does disease severity have a direct relationship with each arthritis self-efficacy domain, and do the self-efficacy domains mediate the relationship between disease severity and RA pain and each area of functioning.
Results: Disease severity was related to pain, physical functioning, and each self-efficacy domain (beta = 0.28-0.56, P < 0.001). Each self-efficacy domain was related to its respective domain of functioning (e.g., self-efficacy for pain was related to pain; beta = 0.36-0.54, P < 0.001). Self-efficacy mediated the relationship between disease severity and pain and functioning (beta = 0.12-0.19, P < 0.001). Self-efficacy for pain control and to perform functional tasks accounted for 32-42% of disease severity's total effect on their respective outcomes (e.g., self-efficacy for pain control accounted for 32% of disease severity's total effect on pain). Variance accounted for by the total model was 52% for pain, 53% for physical functioning, and 44% for affective and social functioning.
Conclusion: Disease severity and self-efficacy both impact RA functioning, and intervening in these areas may lead to better outcomes.
Trial registration: ClinicalTrials.gov NCT00088764.