Impact of Sleep Quality on Cognitive Performance in School-Aged Children with ADHD

Thesis Abstract

Sleep disturbances are prevalent among school-aged children with attention-deficit/hyperactivity disorder (ADHD) and are associated with exacerbated cognitive impairments, daytime behavioral problems, and reduced academic performance. This study addresses the problem of how sleep quality modulates cognitive performance in children with ADHD, aiming to elucidate the mechanisms by which nocturnal sleep parameters influence executive function, attention, and working memory. The objectives are to (1) quantify associations between sleep quality indicators and cognitive performance; (2) determine whether ADHD symptom severity moderates these associations; (3) identify specific sleep dimensions (e.g., sleep efficiency, wake after sleep onset, and sleep onset latency) that best predict cognitive outcomes; and (4) explore potential mediating roles of daytime sleepiness and mood. Guided by the biopsychosocial model and supported by the two-process model of sleep regulation, the study hypothesizes that poorer sleep quality will be significantly related to reduced performance on objective cognitive tasks and that higher ADHD symptomatology will amplify these relationships. A cross-sectional, school-based design was employed. The population comprised children aged 8–12 years with a confirmed ADHD diagnosis drawn from five mainstream primary schools and two clinical outreach centers within a metropolitan area. A total of 320 children were invited, with 280 providing complete data and meeting inclusion criteria (balanced for sex and ADHD subtype). Sleep quality was assessed using actigraphy for seven consecutive nights, the parent-reported Children’s Sleep Habits Questionnaire (CSHQ), and daily sleep diaries to capture objective and subjective sleep parameters. Cognitive performance was evaluated using a battery of standardized neuropsychological measures the Cambridge Neuropsychological Test Automated Battery (CANTAB) subtests for spatial working memory and rapid visual information processing, the Stroop Color-Word Test for inhibition control, and the Wisconsin Card Sorting Test (WCST) for cognitive flexibility. ADHD symptom severity and functional impairment were measured via the Parent and Teacher ADHD Rating Scales (ADHD-RS) and the Strengths and Difficulties Questionnaire (SDQ). Additional covariates included age, sex, comorbid learning disorders, medication status, and socioeconomic adversity. Data were analyzed using a hierarchical analytic approach. Descriptive statistics characterized sample demographics and sleep variables. Multivariate linear regression models examined the association between sleep quality indices (sleep efficiency, total sleep time, wake after sleep onset, sleep onset latency) and cognitive outcomes, controlling for covariates. Structural equation modeling (SEM) tested a hypothesized mediation model with daytime sleepiness and mood as mediators between sleep quality and cognitive performance. Moderation analyses assessed whether ADHD symptom severity moderated the sleep–cognition relationships. Sensitivity analyses conducted to account for medication status and data missingness. The analytic framework integrated the theoretical constructs of the two-process model of sleep regulation and neurocognitive functioning theories of executive control. Expected findings include significant positive associations between higher sleep efficiency and longer total sleep time with better performance on working memory, attention, inhibition, and cognitive flexibility tasks. It is anticipated that daytime sleepiness will mediate a substantial portion of the sleep–cognition relationship, while mood disturbance will partially mediate and ADHD symptom severity will strengthen these associations. The study expects minimal differential effects across ADHD subtypes after adjusting for confounders, though combined-impairment phenotypes may exhibit larger deficits. The study contributes to knowledge by delineating specific sleep parameters most predictive of cognitive deficits in children with ADHD and by clarifying the mechanisms linking sleep to executive functioning in this population. It provides empirical guidance for integrated interventions emphasizing sleep hygiene, behavioral sleep strategies, and coordinated school-based accommodations to mitigate cognitive and academic difficulties. Policy implications include informing clinicians, educators, and parents about prioritizing sleep-focused assessments in ADHD management. The authors recommend longitudinal follow-up to examine causal pathways and intervention studies testing the efficacy of sleep-enhancement programs on cognitive outcomes and academic performance in children with ADHD.