Objective: To determine the relationship between fatigue and disease-related and psychosocial variables in PsA.
Method: 499 patients attending the University of Toronto PsA Clinic were administered the modified Fatigue Severity Scale (mFSS). At the time of mFSS administration, clinical and laboratory measures of disease activity and damage were recorded. Linear regression models were used to examine the cross-sectional relationship between disease-related and psychosocial variables and mFSS scores.
Results: At least moderate fatigue occurred in 49.5% of patients and severe fatigue in 28.7%. Univariately the vast majority of variables were significantly associated with mFSS scores. The final multivariate model was comprised of female sex, SF-36 pain and mental health scales, number of fibromyalgia tender points, HAQ and “ever used” methotrexate and explained 54.5% of the variation in mFSS scores. The SF-36 mental health scale played the largest role in the multivariate model, uniquely accounting for 6.6% of the variation in FSS. The disease-related factors significant at the univariate level did not achieve statistical significance in the context of HAQ and pain measures.
Conclusion: Fatigue is a common symptom in PsA, and is associated, in a multivariate model, with pain, female sex, physical functional disability, medication status and psychological distress. Fatigue appears to provide some information that does not overlap with the core set of outcome domains in PsA.