Preliminary data examining associations of fatigue subtypes with pain, pain interference, sleep quality, and affect across 14 days in adolescents with chronic musculoskeletal pain and pain-free controls

Objective: This preliminary study analyzed existing data from a larger study to characterize fatigue subtypes (general, cognitive, and sleep-related) across 14 days in adolescents with chronic musculoskeletal (MSK) pain and pain-free controls. A secondary exploratory aim was to determine whether fatigue subtypes were associated with next-day pain intensity, pain interference, sleep quality, or positive or negative affect. Methods: Participants were 26 adolescents with chronic MSK pain and 26 pain-free controls matched on age and sex who completed a daily diary assessing fatigue subtypes, pain intensity, pain interference, sleep quality, and affect for 14 consecutive nights. Data were aggregated across all nights for between-group comparisons, and dynamic structural equation models were used to determine how fatigue subtypes were associated with pain, sleep, and affect from one day to the next. Results: Averaging across 14 days, participants in the MSK group reported greater total fatigue and fatigue subtypes than participants in the control group (all p's <. 001). Averaging across days, participants in the MSK group reported higher general fatigue than cognitive (p =. 03) or sleep-related fatigue (p =. 053). In the exploratory within-person analysis, previous day's cognitive fatigue (-0.10, p <. 01) and general fatigue (-0.08, p <. 01) were associated with worse next-day sleep quality in the MSK pain group. In the control group, cognitive fatigue was associated with greater next-day pain intensity (.04; p <. 01) but lower next day pain interference (-0.03; p <. 001). Conclusions: Results preliminarily suggest fatigue subtypes are prevalent and impactful in adolescents with chronic MSK pain. Future replication of results is needed.