Factors associated with fatigue in children with enthesitis/spondylitis-related juvenile idiopathic arthritis: an exploratory cross-sectional study

BACKGROUND: Enthesitis/spondylitis-related juvenile idiopathic arthritis (ESR-JIA) is a subtype of JIA characterized by peripheral arthritis and enthesitis, with possible axial skeleton involvement. Fatigue is a common and challenging symptom in JIA, often persisting despite pharmacological treatment, and may be particularly pronounced in ESR-JIA. It can impair physical and psychological well-being, daily activities, and academic performance. However, factors associated with fatigue in children with ESR-JIA remain poorly understood. METHODS: This cross-sectional study recruited 77 children diagnosed with ESR-JIA. Fatigue was assessed using the Pediatric Quality of Life Inventory Multidimensional Fatigue Scale (PedsQL-MFS) where higher scores indicate less fatigue. Associations between fatigue and clinical disease characteristics, objective clinical measures, subjective patient-reported factors, and blood biomarkers were examined. Spearman correlation analyses and simple and stepwise multivariable linear regression were performed to identify factors associated with fatigue. RESULTS: Univariable linear regression showed body composition parameters (free fat mass, skeletal muscle mass, and skeletal muscle index) and muscle strength (ankle dorsiflexion strength and ankle plantarflexion strength) were positively correlated with PedsQL-MFS total scores. In contrast, pain intensity, depression-related symptoms, and sleep efficiency were negatively associated with PedsQL-MFS total scores. Subsequent stepwise multivariable regression analysis showed pain intensity, depression-related cognitive changes, ankle plantarflexion strength, and sleep efficiency were independently associated with PedsQL-MFS total scores, collectively explaining 33.6% of the variance. CONCLUSIONS: Fatigue in children with ESR-JIA was associated with multiple psychological and physical factors. Lower muscle mass, weaker ankle plantarflexor strength, higher pain intensity, depression-related cognitive changes, and poorer sleep efficiency were associated with more severe fatigue. These findings highlight the multidimensional nature of fatigue in ESR-JIA and support the need for comprehensive fatigue assessment and management.