Sleep Fragmentation and Biomarkers in Juvenile Idiopathic Arthritis

Objectives: (1) To compare sleep (nighttime sleep duration and sleep efficiency) and sleep fragmentation (movement and fragmentation index), as measured by actigraphy, and symptoms (pain and fatigue) in 8- to 14-year-old children with polyarticular and extended oligoarticular juvenile idiopathic arthritis (JIA) and (2) to examine the associations between sleep fragmentation (movement and fragmentation index) and the calcium-binding protein biomarkers S100A12 and myeloid-related protein (MRP8/14). Method: Participants included 40 children with extended oligoarticular (n = 15) or polyarticular (n = 25) JIA and their parents. Serum protein samples were obtained during routine rheumatology clinic visits. Children completed the PedsQL Multidimensional Fatigue Scale and daily pain and sleep diaries and wore actigraphy monitors for 9 consecutive days. Parents completed the Children's Sleep Habits Questionnaire (CSHQ). Results: Of the 40 children, 68% scored above the CSHQ clinical cutoff score for sleep disturbances. Mean nighttime sleep duration was 7.5 hr, and mean sleep efficiency was 85.3%. Group differences were not found for nighttime sleep duration, sleep efficiency, movement and fragmentation index, or S100A12 and MRP8/14 protein concentrations. In a stepwise regression, medications, joint count, and movement and fragmentation index explained 21% of the variance in MRP8/14 concentration. Conclusion: Decreased nighttime sleep duration, poor sleep efficiency, and fragmented sleep were observed in our sample, regardless of JIA category. Sleep fragmentation was a significant predictor of MRP8/14 protein concentration. Additional research is needed to understand the interrelations among sleep fragmentation, effects of medication, and S100A12 and MRP8/14 protein biomarkers in JIA.