Disease and psychosocial factors related to physical functioning in rheumatoid arthritis.

One hundred and fifty-five patients with rheumatoid arthritis (RA) were randomly selected from a tertiary care outpatient rheumatology clinic. Disease, treatment, psychosocial and demographic data were collected to test a biopsychosocial model of Physical Functioning as determined by the Arthritis Impact Measurement Scales (AIMS). Cross-sectional and longitudinal hierarchical and stepwise regression analysis were performed to identify variables associated with Physical Functioning. The results of the hierarchical regression revealed that only the disease and psychosocial sets of variables were significant. Stepwise regression revealed that Disease Severity (disease set) and Arthritis Helplessness (psychosocial set) accounted for 37% (longitudinal) to 60% (cross-sectional 12 months---greater than 12 months) of Physical Functioning variance. Our results suggest a role for the inclusion of psychosocial factors in studies of the development of physical disability in patients with RA.