Variability, quality, and timing: An investigation of the interplay between sleep, cognitive control, and symptoms of attention-deficit/hyperactivity disorder

Abstract

Sleep has been extensively studied, but its role in cognition remains poorly understood. Research points to a particular interplay between intraindividual variability (IIV) in sleep, chronotype, cognitive control, and symptoms of attention-deficit/hyperactivity disorder (ADHD). Previous findings indicate that cognitive control processes are differentially affected by sleep deprivation and restriction, but the influence of day-to-day variability in sleep is less known. Moreover, evening chronotypes have been associated with higher IIV in sleep and an individual’s chronotype can partly explain differences in cognitive performance throughout the day. Lastly, ADHD symptoms have been associated with both cognitive control deficits, higher IIV in sleep, and evening chronotypes. The purpose of this study was to investigate this interplay in a sample of healthy adults. Actigraphy and sleep diaries from 39 participants were used to estimate measures of sleep variability, sleep quality, and sleep timing in a two-week period, while measures of ADHD symptoms were derived from a self-report questionnaire. Performance was estimated for three components of cognitive control with a stop-signal task, a task-switching task, and an n-back task. The study found that evening chronotype and ADHD symptoms were associated with lower sleep quality, but not with each other. Contrary to previous findings, no interaction was observed between the participants’ chronotypes and times of testing for cognitive control performance. Post-hoc results indicated that the inattention dimension of ADHD symptomology was associated with lower performance in the task-switching task, but the measure of total ADHD symptoms was not associated with performance on any of the three cognitive control tasks. The study did not find an association v between IIV in sleep and cognitive control performance, but research in larger samples is needed to detect small-magnitude effects. This study serves as an example of how IIV in sleep can be investigated with high ecological validity, and it highlights the need to consider both variability, quality, and timing in investigations of sleep and cognition.