Are patient self-report measures of arthritis activity confounded by mood? A longitudinal study of patients with rheumatoid arthritis.

OBJECTIVE

To determine the extent to which mood in general, and depression in particular, may confound self-report measures of functional disability, pain, and global arthritis status among patients with rheumatoid arthritis (RA).

METHODS

Twenty-four patients with RA were prospectively examined every 2 weeks for up to 60 weeks. At each examination, self-report measures of functional disability, pain, and global arthritis status were assessed using the Health Assessment Questionnaire, and the clinical measures of swollen and tender joint counts, duration of morning stiffness, grip strength, 50' walk time, and Westergren sedimentation rate were recorded. In addition, patients completed a questionnaire derived from the Profile of Mood States-B (POMS-B), which assessed positive and negative moods, and the Center for Epidemiologic Studies Depression Scale (CES-D) at each examination. The degree to which mood or depression confounded the self-report measures of functional disability, pain, and global arthritis status was estimated using pooled time series regression models that examined the relationship between changes in either mood or depression and changes in each self-report measure over the course of the study, while controlling for the effects of the clinical measures of arthritis activity.

RESULTS

Mood, as measured by the POMS-B scale, explained 2.0% or less of the variation in longitudinal changes in each of the self-report measures, after controlling for the effects of the clinical measures of arthritis activity. Depression, as measured by the CES-D, explained less than 2.0% of the variation in changes in functional disability, but explained 6.0 and 8.0% of the variation in changes in pain and global arthritis status, respectively.

CONCLUSION

Depression may confound self-reports of pain and global arthritis status somewhat, but appears to have minimal influence on self-reported functional disability.