Association between sleep and working memory in children with ADHD: a cross-sectional study

OBJECTIVE/BACKGROUND: This study aimed to examine the relationship between sleep problems and working memory in children aged 5-13 years with attention-deficit/hyperactivity disorder (ADHD). PATIENTS/METHODS: Children with ADHD were recruited into a randomized controlled trial from 21 paediatric practices in VIC, Australia. Cross-sectional data for intervention and control children were pooled at 6 months post randomization for the current analyses (n = 189). Children who met the Diagnostic Statistical Manual of Mental Disorders, 4th Edition (DSM-IV) criteria for ADHD and had a parent-reported moderate/severe sleep problem that fulfilled diagnostic criteria for a behavioural sleep disorder were recruited into the study. Sleep was assessed by detailed parent (Children's Sleep Habits Questionnaire) and self-reports (Self-Sleep Report). Working memory was measured using the Working Memory Test Battery for Children (low and very low working memory defined as <25th and <10th percentiles, respectively). Analyses were adjusted for child age and gender, internalizing and externalizing comorbidities, and socio-economic status. RESULTS: Self-reported sleep problem severity was associated with poorer working memory; for each standard deviation increase in self-reported sleep problems, working memory scores decreased by -3.8 points (95% confidence interval (CI): -6.7, -0.8; p = 0.01). There was some evidence that self-reported sleep problems were associated with low (p = 0.06) and very low working memory (p = 0.01). There was minimal evidence that parent-reported sleep problems were associated with poorer working memory with the exception of bedtime resistance problems. CONCLUSIONS: Behavioural sleep problems and working memory are associated in children with ADHD, particularly when sleep is assessed by self-report.