A comparison of impact of fatigue on cognitive, physical, and psychosocial status in patients with fibromyalgia and rheumatoid arthritis.

This study was performed to compare the impact of fatigue on different aspects of quality of life in patients with rheumatoid arthritis (RA) and fibromyalgia syndrome (FM). This study involved subjects with FM (n = 45) and RA (n = 44). Impact of fatigue on physical, cognitive, and psychosocial status was measured with Fatigue Impact Scale (FIS) and health-related quality of life (HRQoL) with the Medical Outcome Study Short Form 36 (SF-36). Multiple regression analyses were used to evaluate impact of fatigue on quality of life by taking into account clinical symptoms and disease activity scores in these two patient groups. Although the severity of fatigue assessed by FSS was the same in FM and RA; according to Fatigue Impact Scale, fatigue has higher impact on cognitive function in FM (mean ± SD; 28.8 ± 19.9), and on the other hand, it has higher impact on mainly physical component (mean ± SD; 26.3 ± 4.9) in RA. Regarding all the clinical symptoms and disease activity scores, multiple regression models showed that fatigue together with pain affected the HRQoL (SF-36) in both patient groups. Fatigue has different impacts on QoL in FM and RA, respectively. Together with pain, fatigue lead FM patients to see disease as having worse health in terms of mental function, whereas it leads to poor health in terms of physical function in RA.