Correlations of fatigue in Danish patients with rheumatoid arthritis, psoriatic arthritis and spondyloarthritis.

Objective: To describe fatigue in relation to disease-specific and socioeconomic factors and to test possible correlations between fatigue and work impairment, quality of life, pain, sleep, depression, and physical functioning in people with rheumatoid arthritis (RA), psoriatic arthritis (PsA) and axial spondyloarthritis (axSpA).

Methods: A questionnaire-based cross-sectional survey collecting patient characteristics such as disease characteristics, socioeconomic factors and patient-reported outcomes (PROs) from patients with RA, PsA and axSpA in Denmark. PRO scales included the FACIT-Fatigue sub-scale, Work Productivity and Activity Impairment scale (WPAI), EuroQol (EQ-5D), Medical Outcomes Study Sleep Scale (MOS), Major Depression Inventory (MDI), and Health Assessment Questionnaire (HAQ). Respondents were recruited via routine visits to the outpatient rheumatology clinic; information on diagnosis, treatment and disease activity was collected from medical journals by trained nurses.

Results: 487 patients participated in the study. Fatigue was more present in women, experienced patients, and patients who changed medication in the past 12 months, who were unemployed, who had less education, and who had lower household income. There was no statistically significant difference between mean fatigue in the three diagnostic groups (p = 0.08). Fatigue correlated with all included PROs (Pearson correlation coefficients, p<0.0001). Stratifying for diagnosis and adjusting for socioeconomic factors did not change the conclusion.

Conclusion: In a stable, representative group of patients with RA, PsA and axSpA, we found significant correlations between fatigue and work impairment, quality of life, pain, sleep, depression and physical functioning. Fatigue cannot be perceived as a single problem, but rather as a symptom that affects broadly.