Characterizing Fatigue Subtypes in Adolescents with Chronic Musculoskeletal Pain and Pain-Free Controls

Context: General fatigue, sleep-related fatigue, and cognitive fatigue are prevalent and disruptive in adults with chronic musculoskeletal (MSK) pain, but little is known about these fatigue subtypes in pediatric musculoskeletal pain. Objective: To compare fatigue and its subtypes between adolescents with chronic MSK pain and pain-free controls and to test if fatigue subtypes were associated with concurrent pain and its impact (pain intensity, number of pain sites, pain interference, and functional disability) or experimental pain (intensity and tolerance) in adolescents with chronic MSK pain. Finally, we sought to explore adolescents' qualitative characterizations of their fatigue. Methods: Adolescents with chronic MSK pain (12-17 y.o., n = 26) and pain-free controls (n = 26) completed validated self-report measures of fatigue, pain, and functional disability, underwent an experimental pain tolerance task (cold water immersion of the hand), and provided qualitative descriptions of their fatigue (pain group only). Results: Adolescents with chronic MSK pain reported significantly greater general, sleep-related, and cognitive fatigue than pain-free controls (all p's < 0.001). In adolescents with chronic MSK pain, fatigue subtypes were associated with clinical pain and pain impact (r 's = 0.43-0.84) but not experimental pain measures (p's > 0.05). Adolescents with chronic MSK pain qualitatively described the negative implications of the different fatigue subtypes, particularly when perceived as long-lasting. Conclusion: This preliminary study suggests that fatigue subtypes are prevalent and impactful in pediatric patients with chronic MSK pain. When planning multi-disciplinary treatment for pediatric MSK pain, providers should recognize fatigue as another disabling symptom.