Sleep and Cognitive Functioning: The Moderating Role of Vagal Indices

Abstract

This dissertation contains two studies. In the first study, vagal tone and vagal reactivity (indexed by respiratory sinus arrhythmia; RSA) were examined as possible moderators of the associations between both actigraphy and subjective sleep disruptions and multiple aspects of children’s cognitive performance. Children (M age = 8.70 years; N = 166; 3rd grade) wore actigraphs for seven consecutive nights and completed a subjective measure of sleep via interview. To evaluate cognitive functioning, children completed the Woodcock-Johnson III Tests of Cognitive Abilities (WJ III; Woodcock, McGrew, & Mather, 2001) and a computerized reaction time task (Psych/Lab; Abrams, 2004) in the laboratory. Vagal indices were assessed in the lab; RSA was obtained during a three minute baseline and RSA reactivity (RSA-R) was derived as the difference between RSA during a mild cognitive stressor (i.e., star tracing task) and initial RSA. Results suggest that children who exhibited RSA withdrawal to the laboratory stressor (lower RSA during stressor than baseline), and to a lesser extent those who had higher levels of baseline RSA, were protected from the negative effects of sleep disruptions on various executive functioning tests. Building on the first study and following the same procedures, the second study further delineated the role of the parasympathetic nervous system by examining children’s RSA activity (i.e., baseline levels, reactivity to a lab challenge and/or recovery following the challenge) as potential moderators in the link between children’s sleep (self-report and actigraphy-based) and multiple domains of children’s cognitive functioning both cross-sectionally (N = 132; 80 boys; 5th grade) and longitudinally over two years (from 3rd to 5th grade). Cross-sectional results indicate that actigraphy-based sleep variables (i.e., sleep minutes, sleep efficiency, and long wake iii minutes) interact with RSA reactivity (RSA-R) to a problem-solving task to predict children’s Decision Speed scores on the WJ III; cross-sectional findings did not yield significant moderation effects for baseline RSA or RSA recovery. Longitudinal findings show that RSA-R, and to a lesser extent baseline RSA, interact with both self-reported and actigraphy-based sleep parameters to predict multiple WJ III test scores two years later. Results build on the scant literature examining individual differences in the sleep-cognitive functioning link and suggest that interactions between physiological and biological systems are important for the prediction of children’s cognitive functioning.