Statistical analysis
Baseline characteristics were descriptively reported. T-tests and
chi-square tests were used to examine potential differences in age, sex
and tumor location between participants and non-participants (active or
passive refusal), and between participants and patients who were not
approached (due to severe illness/palliative care or logistical issues).
To examine differences in reported sleep between participants and
healthy children, scores of the PROMIS questionnaires were compared to a
mean score of 50, using one-sided t-tests. Statistical significance was
considered as a P -value of <.05. The percentage of
moderate and severe sleep problems was described by using the
questionnaire-specific cut-offs25 and compared to the
normal population by using non-parametric chi-square tests.
Linear regression models were used for comparing actigraphic sleep
estimates between the participants and healthy children. As sleep
estimates are age-dependent, regression models were adjusted for
age28.
Risk factors for impaired sleep were explored by building linear
regression models. Demographic and medical variables relevant for sleep
outcomes were examined with univariate analyses. Variables with aP -value of <.10 were subsequently added to a
multivariable model. A P -value of <.05 was considered
significant. All analyses were carried out with IBM SPSS Statistics
version 26.0.0.1.