Relationship Between Fatigue and Inflammation, Disease Duration, and Chronic Pain in Psoriatic Arthritis: An Observational DANBIO Registry Study

Objective. Fatigue is one of the most significant symptoms, and an outcome of great importance, in patients with psoriatic arthritis (PsA), but associations between underlying components of fatigue experienced by patients in relation to the disease have been sparsely investigated. The objectives were to describe the degree of fatigue in patients with PsA, and to examine important components associated with fatigue. Methods. We performed a cross-sectional survey including patients registered in the Danish nationwide registry DANBIO from December 2013 to June 2014. Principal component analysis (PCA) was used to identify factors associated with fatigue. Results. A total of 1062 patients with PsA were included in the study. A PCA reduced co-variables into 3 components explaining 63% of fatigue in patients. The first component, contributing to 31% of fatigue, was composed of inflammatory factors including swollen and tender joints, physician's global assessment, elevated C-reactive protein (CRP), and high Pain Detect Questionnaire ( PDQ) score. The second component, contributing to 17% of fatigue, consisted of increasing age and long disease duration. The third component, contributing to 15% of fatigue, consisted of high PDQ score, tender joint count, increasing age, and concomitant low CRP, suggestive of a chronic pain component consisting of central pain sensitization or structural joint damage. Conclusion. Fatigue in patients with PsA may be driven by clinical inflammatory factors, disease duration, and chronic pain in the absence of inflammation.