CORDIS

It is well known that sleep-wake neurobiological regulatory processes continue to mature from prenatal stages to late adolescence. Examples of maturational changes include alterations in electroencephalographic activity, temporal distribution of sleep stages, and the ratio of sleep/wake amounts. Although the precise function of sleep remains unknown, these observed universal changes in youth imply that sleep likely serves vital neurobiological and developmental functions. It is therefore not surprising that a growing body of evidence suggests insufficient or inadequate sleep poses adverse consequences on physiological, behavioral, emotional, and academic functioning of adolescents.
Chronic sleep loss has achieved epidemic proportions in youth worldwide, with over three-fourths of teens reporting they are regularly not getting the needed amount of nightly sleep. Sleep deprivation in adolescents and its functional consequences, i.e. sleepiness, mood, behavior, cognition and academic performance, have been significantly understudied. Of the limited studies that have been published, most are methodologically inadequate. Specifically, the majority of studies examining the link between mood, cognition, and sleep have been correlational in nature, using survey or other self-report data. Nonetheless, these important data have alerted us to one of the most difficult social and public health problem facing adolescents today, i.e. chronic sleep insufficiency.
Although correlational data have begun to identify the relationship between insufficient or inadequate sleep and deficits in daytime functioning, it is unable to elucidate the directionality or causality of their potential influences. In other words, experimental research is sorely needed in order to directly manipulate sleep (e.g. in quantity) so as to examine how differing sleep patterns may result in alternative behavioral or emotional outcomes. This study was designed to address this knowledge gap; the main goal of this study is to objectively examine sleep loss and sleep satiation using a monitored behavioral sleep manipulation and examine its effects on neuropsychological, behavioral and emotional functioning in the natural environment in healthy adolescents.
Sleep is a vital necessity for optimal cognitive and behavioral performance and emotional regulation, and may have significant influence on child and adolescent development. Despite the alarmingly high rates of sleep loss among adolescent populations, there have been only a few experimental studies examining this ubiquitous phenomenon and its functional effects. This project has conducted in order to bridge this gap. Therefore, the main objectives of the study were to:
(1) Examine the causal effects of sleep loss on objectively measured neuropsychological functioning, including a range of cognitive areas: attention, learning, memory, processing speed, motor skills, problem solving, and executive functions.
(2) Examine the causal effects of sleep loss on subjective measures of mood, emotional regulation, and sleepiness, among others.
(3) Examine the causal effects of sleep loss on behavior, such as academic performance, social activity, at risk behavior, and more.
(4) Examine direct and indirect effects of sleep on the above variables as well as possible mediating and moderating effects between sleep and functioning in adolescents.
In order to achieve these goals, a mixed-model repeated measures design was devised and conducted. The vast majority of assessments were conducted during the summer holidays or other school breaks. Each participant underwent two experimental conditions, "sleep restriction" and "sleep extension," in counterbalanced order. In the restriction condition, the teens were asked to be in bed 6-6.5 hours per night, from approximately 1:00AM to 7:00AM, for four consecutive nights. In the extension condition, teens were asked to spend 10-10.5 hours in bed per night, approximately 11:00PM to 9:00AM, for four consecutive nights. In addition, in order to neutralize possible carryover effects, there was a 1-3 week washout period between the sleep conditions, and teens were asked to maintain their regular sleep schedule prior to each experimental condition. So as to make sure teens adhered to the prescribed sleep schedule, all participants wore actigraphs (Ambulatory Monitoring, Inc., Ardsley, NY) and kept detailed sleep diaries during experimental conditions.
Each participant underwent a 45-minute computerized neuropsychological test battery (NeuroTrax™, Houston, TX) at three timepoints, i.e. at baseline and following each sleep condition. Each testing session included different versions of the tasks designed to reduce possible learning effects. The initial baseline condition served as an introduction to the testing procedure. All batteries were conducted on a laptop computer between 8:30AM and 9:30AM in order to specifically examine possible effects of sleep on cognition during the early morning school hours, which tend to be the most difficult for high school students. During these visits, teens also completed questionnaires asking about their mood, sleep, sleepiness, and behavior. The complete battery includes a Verbal and a Non-verbal Memory Test (immediate and delayed portions), a Verbal Function Test, Problem Solving Test, Visual Spatial Processing Test, Go-NoGo, Stroop, Finger Tapping, Catch Game, and the Staged Information Processing Test and takes approximately 45 minutes to complete. Participants in this study were administered the complete Hebrew-version of the battery with the exclusion of the Verbal Function task, due to an observed ceiling effect in the performance during the early phases of the study. In addition, participants filled out a range of questionnaires on their mood, behavior, academic performance, and general functioning.
Preliminary findings from this study suggest accumulated sleep debt in adolescents may underlie objectively-measured deficits in multiple cognitive areas, such as sustain attention, motor skills, information processing speed, and executive functions.