Participants and procedures
The Princess Máxima Center for Pediatric Oncology opened in 2018 and is a Dutch nationwide center where specialized pediatric oncology care is centralized. A small number of patients with a low grade brain tumor, requiring neurosurgery only, are treated in former pediatric oncology centers. All new patients with a primary brain tumor diagnosis between January 2019 and October 2021 and treated at the Princess Máxima Center were eligible if they were between the age of 6 and 16 years, had sufficient understanding of the Dutch language, had no evident pre-existing developmental delay and did not receive end-of-life care. All participants and their parents/caregivers provided written informed consent. Sleep assessments took place around four weeks after the child entered the hospital, with a maximum of three months. This study was reviewed and approved by the Clinical Research Committee of the Princess Maxima Center and confirmed subsequently by the Medical Research Ethics Committee of the University Medical Center Utrecht.