Serum cytokine levels related to multiple dimensions of fatigue in patients with primary Sjogren's syndrome

Objective: To test whether serum levels of selected cytokines relate to different dimensions of fatigue in patients with primary Sjogren's syndrome (pSS). Methods: Sixty female patients with pSS filled out a questionnaire to assess multiple dimensions of fatigue. Scores were compared with values in a population based control group (n = 139). Levels of interleukin (IL) 1beta, IL2, IL6, IL10, and tumour necrosis factor alpha were measured in serum with commercial sandwich ELISAs. The relationship between self reported dimensions of fatigue and these serum cytokine levels was determined. Results: Patients with pSS had high scores at all dimensions of fatigue ( p< 0.001): general fatigue, physical fatigue, reduced activity, reduced motivation, and mental fatigue. Fatigue levels were not related to serum cytokine levels. The incidental finding that reduced motivation was higher in patients with detectable serum levels of IL10 ( p = 0.04) disappeared after correction for multiple testing. Conclusion: Fatigue is prominent in patients with pSS and involves all dimensions of fatigue. The findings do not suggest a widespread effect of circulating cytokines on multiple aspects of fatigue.