Objectives: Fatigue is a prominent symptom in many rheumatic diseases and has a substantial impact on many outcomes. In previous research, fatigue has been linked with poor sleep and discomfort, including joint pain and sicca symptoms. The aim of the present study was to investigate prospectively the daily variations in fatigue and the roles of discomfort and adequacy of sleep the previous night in that fatigue for people with primary Sjögren's syndrome (pSS) or rheumatoid arthritis (RA).
Methods: Thirty-nine women with pSS or RA reported their discomfort and fatigue for 35 days using the Profile of Fatigue and Discomfort. Sleep was monitored with wrist actigraphy, and the quantity and quality of the night's sleep was reported in a diary each morning.
Results: The pattern of fatigue did not differ significantly between women with pSS and women with RA. For participants with either condition, both somatic and mental fatigue increased steadily throughout the day. Multi-level regressions indicated that evenings of worse discomfort were followed by poorer reported quantity/quality of sleep and worse sleep efficiency (percentage of time asleep when in bed). In addition, a night of worse discomfort and poor sleep was followed by more severe fatigue compared with the individual's average.
Conclusions: Fatigue management for people with rheumatic disease could include strategies for coping with discomfort at night and difficulties in sleeping. Further research into ameliorating fatigue should include assessments of persistent discomfort or periods of insomnia and identify disease-specific needs that require targeted intervention.