Background
Sleep disturbances and fatigue are frequently experienced (40-70 %) in patients with rheumatoid arthritis (RA) and contribute to decreased quality of life and adverse health and behaviour consequences. However, little is known about the prevalence of poor sleep and its association to Physical Activity (PA) and fatigue. Understanding PA, fatigue and the impact on sleep disturbances could illuminate ways to promote sufficient sleep in RA patients. Thus, the aim of this study was to examine the association between sleep disturbance, PA, and fatigue.

Methods
A total of 500 RA patients from a rheumatology outpatient clinic were recruited consecutively to participate in an observational cross-sectional study. The self-administered questionnaire covered the Health Assessment Questionnaire (HAQ), Visual Analogue Scale (VAS) for pain and fatigue, Physical Activity Scale (PAS), Multidimensional Fatigue Inventory (MFI), Short Form SF-12v2, Epworth Sleepiness Scale (ESS) and Pittsburgh Sleep Quality Index (PSQI) as well as demographic data and clinical data (comorbid condition, disease duration, disease activity).

Results
The response rate was 89%. All participants were between 22 and 88 years old (mean age of 58 years), and 80% were women. The mean disease duration was 14 years and mean DAS score was 2.7. The prevalence of poor sleep quality was 61 %. Higher level of general fatigue, mental fatigue, physical fatigue, reduced activity and reduced motivation was reported in patients with poor sleep quality compared with patients with good sleep quality (P<0.0001). Sleepiness (P=0.0007), sleep duration, sleep latency, sleep disturbance and daytime dysfunction was also higher in patients with poor sleep quality then in patients with good sleep quality (P<0.0001). For the purpose of this study, the participants were divided into two categories. Poor sleep quality (PSQI global score >5) and good sleep quality (PSQI global score <5). More time spent on sedentary leisure time (P=0.0371) and moderately strenuous PA was reported in patients with poor sleep quality compared with patients with good sleep quality, but there were no significant differences between light PA and hard strenuous PA on sleep quality.

Conclusion:
A high prevalence of sleep disturbances was observed. This study indicates that PA and fatigue play a significant role in self-reported sleep quality. Addressing sleep disturbances via pharmacological and behavioural interventions may have a critical impact on RA patients.