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624 The association of circadian rhythms with cognitive functioning in children with attention-deficit hyperactivity disorder


 
 
 Disrupted circadian rhythms is associated with impaired cognitive function. Although circadian rhythm disturbances are commonly seen in individuals with attention-deficit hyperactivity disorder (ADHD), whether their cognitive functioning is thus affected remains unclear. This study aimed to examine the associations of circadian-related parameters with different cognitive abilities in children with ADHD.
 
 
 
 Fifty-seven children with ADHD were recruited into this study (age range: 6–12 years, 66.7% male). They were assessed by parent-report questionnaires on sleep problems (Children’s Sleep Habits Questionnaire, CSHQ), and ADHD symptoms (Strengths and Weaknesses of ADHD Symptoms and Normal Behaviour Scale). Actigraphic data collected for seven consecutive days were analyzed using parametric and nonparametric methods. Cognitive functioning was assessed with Continuous Performance Test (CPT) for sustained attention, Letter-digit test for processing speed, Digit Span test and N-back task for working memory, Tower of London test for planning skills and Bergs Card Sorting Test for set-shifting ability. The relationship between circadian parameters and cognitive performance was analyzed using multiple regression while controlling for age, sex, ADHD medication, the day of cognitive assessment (school days vs non-school days), total sleep time, and CSHQ total score.
 
 
 
 Increased activity during the most active 10-h period of the day (St. β = 0.39, p = 0.012) was related to more omission errors on CPT, and later onset of the least active 5-h period of the day (St. β = 0.44, p = 0.004) was associated with longer correct reaction time on CPT. Lower relative amplitude was associated with poorer performance on Digit Span (St. β = 0.33, p = 0.042). No significant associations were found between the circadian-related parameters and the performance on other tasks measuring processing speed and executive functions.
 
 
 
 Circadian rest-activity rhythms (blunted rest-activity rhythms, higher daytime activity, and later onset of nocturnal rest) were associated with cognitive functioning in ADHD children. Future longitudinal studies are needed to explore the long-term impact of circadian rhythm disturbances and the effects of circadian-focused intervention on cognitive functioning in ADHD children.
 
 
 
 This work was supported by the Health and Medical Research Fund (Project No.: 30160604).
