Effects of disease activity, pain, and distress on activity limitations in patients with systemic lupus erythematosus.

Abstract

OBJECTIVE: To evaluate the extent to which disease activity, pain, and psychological distress predict activity limitations in persons with systemic lupus erythematosus (SLE). METHODS: A sample of 93 persons with SLE completed medical and psychosocial evaluations at one study visit. Sets of measures were chosen to represent constructs of Disease Activity, Pain, Distress, and Activity Limitations. Confirmatory factor analysis was conducted to determine if the measures fit the intended constructs, and structural equation modeling was used to evaluate the direct effects of Disease Activity, Pain, and Distress on Activity Limitations, as well as indirect effects of Disease Activity as mediated by Pain and Distress, and indirect effects of Pain as mediated by Distress. RESULTS: The confirmatory factor analysis indicated a good fit of the measures to their intended constructs. The overall model predicting Activity Limitations based on Disease Activity, Pain, and Distress accounted for 68% (p < 0.001) of the variance in perceived Activity Limitations. Severity of Pain was the only construct that was directly associated with Activity Limitations (r = 0.70, p < 0.001). The effects of Disease Activity on Activity Limitations were primarily indirect via its influence on Pain. Distress was not significantly associated with Activity Limitations. When Distress was trimmed from the model, the remaining constructs accounted for 66% of the variance in Activity Limitations (p < 0.001). CONCLUSION: Disease Activity and Pain accounted for a substantial proportion of the variance in Activity Limitations. Pain Severity was the strongest predictor of Activity Limitations. This study highlights the importance of adequate pain management for maintaining quality of life in persons with SLE.