The role of fatigue in functional outcomes for youth with chronic pain.

Background: As a complex multidimensional construct, fatigue may play an important role in the physical and psychosocial functioning of youth with chronic pain. Based on a model previously tested in adults, the current study similarly utilized patient-reported outcomes measurement system (PROMIS) to examine how fatigue contributes to functional outcomes for youth with chronic pain. The model tested self-reported ratings of pain intensity, depressive symptoms and sleep disturbance as predictors of outcomes (mobility, pain-related interference and school functioning) as mediated by ratings of fatigue.

Methods: Two hundred and eighty-five youth with chronic pain ages 8-17 years and their caregivers, completed surveys as part of their initial clinical evaluation at a tertiary paediatric pain clinic. Study measures included: paediatric PROMIS domains (mobility, pain interference, sleep disturbance, fatigue and depressive symptoms), Paediatric Quality of Life school functioning and pain intensity. All mediated effects were calculated via a 1,000-draw bootstrap estimation method in Mplus.

Results: Fatigue was found to be a statistically significant mediator of the effects of pain intensity, sleep disturbance and depressive symptoms on outcomes of pain interference, mobility and school functioning. While pain intensity was found to independently contribute to mobility and pain interference, depressive symptoms did not show significant effects on any outcome beyond its association with fatigue. Sleep disturbance predicted pain interference while fatigue predicted school functioning.

Conclusions: Findings suggest that fatigue is an important intervening factor for functional outcomes among youth with chronic pain. Targeting fatigue may be effective in optimizing school functioning and reducing the deleterious effects of depressive symptoms.

Significance: This cross-sectional study highlights fatigue as a potential clinical target by applying a path analytic model to understand its possible significance and distinction from overlapping constructs such as pain intensity, depression and sleep disturbance. Further study of fatigue may be important in understanding its importance in treatment of paediatric chronic pain.