Els van de Vijver

93 Functional factors Only one paper focused on functional capacity in relation to fatigue and used a wearable device to plot activity over time; this study did not find a significant difference between patients with IBD and healthy controls. It is rather surprising that only one paper looked at functional capacity in adolescents with IBD because it is a frequently used outcome measurement in other chronic diseases.(24-27) Comparison with adult-oriented publications In 2010, a systematic review (3) identified 10 papers about fatigue in patients with IBD and mentioned that the topic deserved more attention, as the prevalence of fatigue approached 50% in patients with IBD in remission and up to 86% in patients with active IBD. Cuzber-Dochan and colleagues published a systematic review in 2013 that included 28 papers on adults, and they concluded that the use of terminology regarding fatigue is inconsistent and that knowledge of the causes, severity and ways of measuring IBD fatigue is incomplete.(28) Three years later, the same research group repeated the literature search and identified a number of psychosocial and physical factors that could potentially be modified through targeted health interventions to improve fatigue in IBD. As in this study, they concluded that fatigue is multifactorial and is associated with active disease, poor sleep quality, anxiety and depression, but the complex interplay between these factors has yet to be deciphered.(29) In studies among adolescents, disease activity and sleep quality are also related to fatigue, but the relationship with anxiety and depression is unclear. Approximately one-quarter of adolescents with IBD have somatic or cognitive symptoms of depression (30), and this is comparable with the prevalence observed in their healthy peers. Depression among adult patients with IBD, on the other hand, is more common compared to among control subjects.(12, 31-33) Previous studies described a poor to low degree of parent-adolescent agreement on psychosocial symptoms.(17, 30) Moreover, adolescents and parents report different symptoms. Therefore, to gain a comprehensive picture of the complaints in adolescents with IBD, both the adolescents and their parents need to be questioned.(34) Systematic review: fatigue 93