CONCISE REPORTS Factors associated with fatigue in patients with systemic lupus erythematosus

Objective—To examine the relation between fatigue, disease activity, damage, and quality of life measures in patients with systemic lupus erythematosus (SLE). Methods—Consecutive patients attending the University of Toronto Lupus Clinic were studied. Disease activity was assessed using the SLEDAI and SLAM-R and damage using the SLICC/ACR Damage index. Fatigue was measured by the Fatigue Severity Score (FSS) and health status by the SF-36 questionnaire. In all cases a tender point count was also performed. Results—81 patients were studied. Their mean (SD) age and disease duration were 43 (12.5) years and 12.7 (8.0) years respectively. The FSS did not correlate with the SLEDAI nor with the SLAM-R. There was no correlation with the SLICC damage index. Fatigue severity correlated with the tender point count (SCC r=0.46, p<0.001), and negatively with all domains of the SF36 (r values −0.50 to −0.82). Disease activity and damage accounted for only 4.8% and 4% respectively of the variance in fatigue severity reported by patients. Conclusion—In an outpatient population of SLE patients, fatigue severity correlates with poor health status and a higher tender point count. In patients with SLE, factors associated with quality of life and fibromyalgia seem to have a greater influence on the severity of reported fatigue than does the level of current disease activity. (Ann Rheum Dis 1999;58:379–381) Fatigue is a very common symptom in systemic lupus erythematosus (SLE) and is described in over 50% of patients at some time during their illness. 2 The cause of fatigue seems to be multifactorial although it is often interpreted as reflecting active disease. As such, it is included in several indices of disease activity. However, other conditions associated with fatigue also occur frequently in SLE including fibromyalgia, which has been reported in up to 22% of patients. 5 In a previous study, we found that disease activity as assessed by the SLEDAI did not correlate with patients’ reporting of fatigue. This study suggested that fatigue was more closely associated with quality of life (QOL) (measured by the Medical Outcome Survey (MOS) SF-20), depression, and fibromyalgia. The potential contribution of accumulated organ damage to fatigue was not assessed. The purpose of this study was to further examine which dimensions of disease in SLE are most closely associated with fatigue. We studied the relation of fatigue with disease activity using two indices, one that includes (SLAM-R) and one that excludes (SLEDAI) fatigue. We also assessed the relation of fatigue with overall damage, tender point count, and health related QOL, using the MOS SF-36, which is the accepted QOL measure for studies of SLE.