Els van de Vijver

110 of-life (IMPACT III) and depression (PedsQL Depression inventory), and were compared to healthy controls. This is the only other cohort in which fatigue was assessed with the PedsQL TM fatigue scale. Like us, they concluded that adolescents with IBD are significantly more fatigued than healthy controls, even when clinical remission was reached. The 6MWD as a proxy of exercise capacity has been used in many other chronic conditions, including congenital heart disease (33), cystic fibrosis (34) and juvenile idiopathic arthritis (35), but not yet in IBD. A German case-control study evaluated exercise capacity in adolescents with IBD with a wearable device (Sensewear Pro 2) to plot spontaneous physical activity over time.(36) Contrary to our observations, the exercise capacity was not different between patients with IBD and healthy controls. Werkstetter and colleagues included 39 IBD patients only, which may have been a too small sample size to detect a group difference. Recently published adult studies on fatigue and IBD show results that are similar to ours.(37-39) These studies also suggest that fatigue negatively impacts on quality-of-life and is not associated with biological factors such as anaemia or persistent mucosal inflammation. Fatigue was rather associated with behavioural factors such as anxiety, depression and sleep disturbances.(37-39) Methodological strengths and limitations The cross-sectional design of this study does not allow to evaluate causality between fatigue and biological parameters. A prospective intervention study to evaluate whether iron supplementation reduces fatigue, improves exercise capacity and quality of life in paediatric patients, is currently underway.[toetsingonline NL42995.096.12) Also, the use of self-report questionnaires may have underestimated the prevalence of fatigue, as patients with low exercise capacity and anaemia may tend to adapt to a lower level of activity and accept this as is. Implications for clinical practice and future research The impact of fatigue on quality-of-life justifies a thorough evaluation of possible causal factors, including behavioural factors such as psychological distress and sleep disturbances. Cognitive Behavioural Therapy has recently been shown to be an effective Chapter 6 110