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

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). 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. 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. 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.

Déclaration de conflit d'intérêts

We have read the journal’s policy and the authors of this manuscript have the following competing interests: SES and MEM report grants from Pfizer Denmark during the conduct of the study and grants from Pfizer Denmark outside the submitted work. SES and MEM are employees of Incentive, which was a paid vendor of Pfizer Denmark and a commercial company. BAE is an employee of Rigshospitalet and University of Copenhagen and reports personal fees from Pfizer Denmark during the conduct of the study and grants from Pfizer Denmark and personal fees from Pfizer Denmark outside the submitted work. LH is a former employee of Pfizer Denmark and TP is an employee of Pfizer Denmark (www.pfizer.dk) and reports salaries from Pfizer Denmark. There are no patents, products in development, or marketed products associated with this research to declare. This does not alter our adherence to PLOS ONE policies on sharing data and materials.