Background Fatigue is a prevalent and debilitating problem in Sjögren's syndrome. It has been suggested that physical activity and cognitions about physical activity can influence fatigue.

Objective The aim of this study was to examine fatigue and physical activity levels in patients with Sjögren's syndrome and the associations of physical activity and physical activity cognitions with fatigue.

Methods In 300 patients with primary Sjögren's syndrome and 100 demographically matched people from the general population (mean age 57 years, 93% female), fatigue (five dimensions of the multidimensional fatigue inventory) and physical activity (three dimensions of the international physical activity questionnaire) were assessed. The physical activity cognitions ‘activity avoidance’ and ‘somatic focus’ of the Tampa scale of kinesiophobia were assessed in the Sjögren's group only.

Results Sjögren's patients had higher scores on all five fatigue dimensions (p<0.001) and lower scores on moderate and vigorous intensity activity (p≤0.001) compared with control participants. In the Sjögren's group, lower physical activity and higher activity avoidance and somatic focus were associated with more severe fatigue on most fatigue dimensions. For general fatigue and physical fatigue, especially the combination of low physical activity and high activity avoidance was associated with more severe fatigue (p<0.05).

Conclusions The results suggest that fatigue in patients with Sjögren's syndrome might be reduced by targeting both physical activity and physical activity cognitions. This suggestion requires verification in clinical experimental studies.