Cognitive dysfunction in adolescents with chronic fatigue: a cross-sectional study

OBJECTIVE To compare cognitive function in adolescents with chronic fatigue with cognitive function in healthy controls (HC). STUDY DESIGN Cross-sectional study. SETTING Paediatric department at Oslo University Hospital, Norway. PARTICIPANTS 120 adolescents with chronic fatigue (average age 15.4 years; range 12-18) and 39 HC (average age 15.2 years; range 12-18). METHODS The adolescents completed a neurocognitive test battery measuring processing speed, working memory, cognitive inhibition, cognitive flexibility, verbal learning and verbal memory, and questionnaires addressing demographic data, depression symptoms, anxiety traits, fatigue and sleep problems. Parents completed the Behaviour Rating Inventory of Executive Function (BRIEF), which measures the everyday executive functions of children. RESULTS Adolescents with chronic fatigue had impaired cognitive function compared to HC regarding processing speed (mean difference 3.3, 95% CI 1.1 to 5.5, p=0.003), working memory (-2.4, -3.7 to -1.1, p<0.001), cognitive inhibition response time (6.2, 0.8 to 11.7, p=0.025) and verbal learning (-1.7, -3.2 to -0.3, p=0.022). The BRIEF results indicated that everyday executive functions were significantly worse in the chronic fatigue group compared to the HC (11.2, 8.2 to 14.3, p<0.001). Group differences remained largely unaffected when adjusted for symptoms of depression, anxiety traits and sleep problems. CONCLUSIONS Adolescents with chronic fatigue had impaired cognitive function of clinical relevance, measured by objective cognitive tests, in comparison to HC. Working memory and processing speed may represent core difficulties.