Correlation of fatigue with pain and disability in rheumatoid arthritis and osteoarthritis, respectively

Objectives: To investigate the correlation of fatigue with pain in rheumatoid arthritis patients and with disability in osteoarthritis patients. Methods: Twenty patients with rheumatoid arthritis and 20 patients with osteoarthritis were evaluated. The degree of fatigue: was evaluated with a visual analogue scale and the Multidimensional Assessment of Fatigue. Pain was evaluated with a visual analogue scale as well as Patient Global Assessment. For disability evaluation, the Health Assessment Questionnaire was performed. Age, gender, disease duration, education, income, antirheumatic drugs used and comorbidity were also obtained. Statistical analysis included Fisher exact, Shapiro-Wilk, Kruskal-Wallis and Spearman tests. The significance level was 0.05. Results: Fatigue was more significantly increased in patients with osteoarthritis than in patients with rheumatoid arthritis when evaluated with Multidimensional Assessment of Fatigue (P<0.05). Pain was found to correlate with fatigue evaluated with visual analogue scale or Multidimensional Assessment of Fatigue in patients with rheumatoid arthritis (r = 0.46; P<0.05). Health Assessment Questionnaire was associated with fatigue visual analogue scale in patients with osteoarthritis (r = 0.54; P<0.05). Patient Global Assessment correlates with fatigue visual analogue scale (r = 0.44; P<0.003). Patients were similar in both groups: all females, similar mean age, with long disease duration and low income. Conclusions: Our results corroborate that fatigue in rheumatoid arthritis patients correlates with the degree of pain, while in osteoarthritis patients it is associated with disability. Therefore, we found that fatigue has different correlates in osteoarthritis and rheumatoid arthritis, and we suggest that disability, not pain, is a correlate of fatigue in osteoarthritis patients.