title: A comparison of fatigue correlates in rheumatoid arthritis and osteoarthritis: disparity in associations with disability, anxiety and sleep disturbance.
abstract: OBJECTIVE
  To investigate correlates of fatigue among individuals with RA and OA, including mood, sleep, disease activity and radiographic damage.
  
  
  METHODS
  Fatigue was assessed using the Multidimensional Assessment of Fatigue-Global Fatigue Index (MAF-GFI) in 103 patients with RA and 103 with OA. Sleep disturbance and pain were assessed using a visual analogue scale anxiety and depression using the Hospital Anxiety and Depression scale and disability using the HAQ. In the RA cohort, the disease activity score-28 joint count (DAS-28) and the Van der Heijde modified Sharp score were calculated, and in the OA cohort, the Kellgren-Lawrence score and the WOMAC score calculated.
  
  
  RESULTS
  The MAF-GFI scores were higher in the OA cohort (P = 0.02). This was not significant after controlling for disability (P = 0.59). OA participants reported greater pain, disability, depression and sleeplessness than those with RA (all P < 0.01). The strongest correlates of fatigue in the RA cohort were depression (P < 0.001) and anxiety (P < 0.001). There was no significant association with pain (P = 0.43), DAS-28 (P = 0.07), HAQ (P = 0.10) or Sharp score (P = 0.78). In OA, the correlates of fatigue were older age (P = 0.02), sleep disturbance (P = 0.03), depression (P = 0.04), disability (P = 0.04) and lower CRP (P = 0.001).
  
  
  CONCLUSIONS
  Fatigue is common and severe in both RA and OA. In RA, fatigue had no significant association with pain, disease activity, disability or erosions, but was associated with depression and anxiety. The disparity in correlates indicates that generalizing the experience of fatigue between OA and RA is not appropriate. Fatigue is an important domain in the assessment of disease impact.
authors.affiliation: Department of Medicine, Dunedin School of Medicine, University of Otago, PO Box 913, Dunedin, 9054, New Zealand. simon.stebbings@otago.ac.nz
authors.forename: Simon
authors.initials: S
authors.lastname: Stebbings
authors.forename: Peter
authors.initials: P
authors.lastname: Herbison
authors.forename: Terrence C H
authors.initials: TC
authors.lastname: Doyle
authors.forename: Gareth J
authors.initials: GJ
authors.lastname: Treharne
authors.forename: John
authors.initials: J
authors.lastname: Highton
mesh_terms: D000328:Adult; D000368:Aged; D001007:Anxiety / Q000209:etiology*; D001172:Arthritis, Rheumatoid / Q000150:complications* / Q000523:psychology; D004185:Disability Evaluation; D004812:Epidemiologic Methods; D005221:Fatigue / Q000209:etiology* / Q000523:psychology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010003:Osteoarthritis / Q000150:complications* / Q000523:psychology; D010147:Pain Measurement / Q000379:methods; D012893:Sleep Wake Disorders / Q000209:etiology*; D055815:Young Adult