Author(s): LIANG, X., QIU, H., XU, R.H., LIU, N., CHEN, M., Institution: THE EDUCATION UNIVERSITY OF HONG KONG, Country: HONG KONG, Abstract-ID: 742

INTRODUCTION:
Attention-deficit/hyperactivity disorder (ADHD) is a pervasive childhood psychiatric disorder characterised by persistent, age-inappropriate levels of inattention, impulsivity, and hyperactivity. ADHD symptoms are thought to reflect underlying impairments in executive function, leading to multiple complications in childhood, such as social impairments, mental health problems, and sleep and circadian disorders. Physical activity (PA) interventions to improve executive function and circadian rhythms in children with ADHD have attracted considerable attention in recent years. The purpose of this study is to examine the direct effects of the intervention on executive function and the indirect effects on executive function via circadian rhythms.
METHODS:
Sixty-three children with ADHD aged 6–12 were recruited and randomly assigned to a 12-week PA intervention group (three 60-minute sessions per week; n = 32, Mage = 8.43 ± 1.39) or a control group (n = 31, Mage = 7.97 ± 1.05). Measurements were conducted at two assessment points: baseline (T1) and post-intervention (immediately after the intervention, T2). Sleep and circadian rhythms were evaluated using the ActiGraph GT3X (ActiGraph, Pensacola, FL, USA) for seven consecutive days. Executive functions were measured using three neurocognitive EF tasks, namely inhibitory control (Eriksen arrow flanker task), working memory (Tower of London), and cognitive flexibility (Trail Making Test via computer-based Inquisit Lab® 6; Millisecond; Seattle, WA, USA).
RESULTS:
The average duration of moderate-to-vigorous physical activity (MVPA) was 43.21 ± 3.24 minutes per session, and the mean Heart Rate (HR) was 145.41 ± 6.54 beats per minute (76.94% of HRmax) as monitored by a Polar heart rate monitor (Polar Verity). The results showed a significant group × time interaction effect, including inhibitory control (F = 6.95, p = .011; η2 = .110) as measured by the arrow flanker test and cognitive flexibility (F = 8.19, p = .006; η2 = .128) as evaluated by the trail making test. A significant group × time interaction effect was observed for circadian rest–activity rhythms as measured by actigraphy for seven consecutive days, including interdaily stability (F = 31.15, p < .001; η2 = .357) and relative amplitude (F = 4.09, p = .048; η2 = .068). We found a weak correlation between changes in relative amplitude and changes in inhibitory control (arrow flanker test reaction time) (r = -0.306, p = 0.013) in the intervention group (n = 32).
CONCLUSION:
Although the PA intervention is beneficial for improving circadian rhythms and EFs in children with ADHD, the pilot RCT is insufficient to establish causality. Given the risks posed by executive dysfunctions and the fact that behavioural sleep problems and irregular circadian rhythm can lead to an increased risk of executive dysfunctions in children with ADHD, circadian rhythm disturbances are a pivotal risk factor for executive dysfunctions in youth with ADHD.