Reliability of sleep spindle measurements in adolescents: How many nights are necessary?

Evidence of night-to-night variation in adolescent sleep spindle characteristics is lacking. Twelve adolescents (M = 15.8 ± 0.8 years, eight males) participated in a laboratory study involving 9 nights with 10 hr sleep opportunity. Sleep electroencephalograph was analysed and intra-class coefficients calculated to determine the reliability of sleep spindles across multiple nights of recording. Slow spindle amplitude and fast spindle density, duration and amplitude characteristics all had acceptable reliability within a single night of sleep recording. Slow spindle density and duration measurements needed a minimum of 4 and 2 nights, respectively, for reliable estimation. Theoretical and methodological implications are discussed.

An experimental study of adolescent sleep restriction during a simulated school week: changes in phase, sleep staging, performance and sleepiness.

This laboratory study investigated the impact of restricted sleep during a simulated school week on circadian phase, sleep stages and daytime functioning. Changes were examined across and within days and during a simulated weekend recovery. Participants were 12 healthy secondary school students (six male) aged 15-17 years [mean = 16.1 years, standard deviation (SD) = 0.9]. After 2 nights with 10 h (21:30-07:30 hours), time in bed was restricted to 5 h for 5 nights (02:30-07:30 hours), then returned to 10 h time in bed for 2 nights (21:30-07:30 hours). Saliva was collected in dim light on the first and last sleep restriction nights to measure melatonin onset phase. Sleep was recorded polysomnographically, and the Psychomotor Vigilance Task (PVT) and Karolinska Sleepiness Scale were undertaken 3-hourly while awake. Average phase delay measured by melatonin was 3 h (SD = 50 min). Compared to baseline, sleep during the restriction period contained a smaller percentage of Stages 1 and 2 and rapid eye movement (REM) and a greater percentage of Stage 4. PVT lapses increased significantly during sleep restriction and did not return to baseline levels during recovery. Subjective sleepiness showed a similar pattern during restriction, but returned to baseline levels during recovery. Results suggest that sustained attention in adolescents is affected negatively by sleep restriction, particularly in the early morning, and that a weekend of recovery sleep is insufficient to restore performance. The discrepancy between sleepiness ratings and performance may indicate a lack of perception of this residual impairment.

Sleep Loss and Affective Functioning: More Than Just Mood.

Empirical evidence supports an intimate link between sleep and affective functioning. While the bidirectional relationship between sleep duration and mood is well documented, limited research targets other aspects of affective functioning, such as emotion and emotion regulation, or considers their interrelationships. The present review summarizes research examining the relationship between sleep and emotion, emotion regulation, and mood, and presents a theoretical model representing the relationships between these constructs. Disruptions to sleep and mood may trigger and maintain a negative cascade, leading to more entrenched sleep problems and psychopathology. Given that insufficient sleep is a widespread phenomenon, understanding the interrelationships between sleep and affective functioning has implications for both public health and clinical practice.

Adolescents who perceive fewer consequences of risk-taking choose to switch off games later at night.

AIM: Technology use by adolescents close to bedtime commonly leads to sleep problems, and individual factors predicting those at heightened risk are under studied. We investigated whether risk-taking perceptions influenced length of adolescent technology use at bedtime and whether being aware of time moderated this association. METHODS: We recruited 16 males and five females, with a mean age of 17.6 years, from school and university populations to assess adolescent technology use and bedtimes. They were assessed for trait risk-taking using the Cognitive Appraisal of Risky Events questionnaire and had unrestrained access to a video game on two separate nights, counterbalanced for clock present or clock absent conditions. The adolescents' self-selected bedtime provided a measure of the level of technology use and was the dependent variable. RESULTS: Adolescents who perceived fewer negative consequences of risky activities on the Cognitive Appraisal of Risky Events played the video game longer and went to bed later than those who perceived more negative consequences (p = 0.03). There was no influence on bedtimes from perceived benefits of risk-taking or clock presence. CONCLUSION: Adolescents who perceived fewer negative consequences of risk-taking were more likely to stay up later using technology, facing a heightened risk of displaced sleep.

Single night video-game use leads to sleep loss and attention deficits in older adolescents.

The present study investigated adolescent video-game use prior to bedtime and subsequent sleep, working memory and sustained attention performance. Participants were 21 healthy, good-sleeping adolescents (16 male) aged between 15 and 20 years (M = 17.6 years, SD = 1.8). Time spent video-gaming and subsequent sleep was measured across one night in the sleep laboratory. There were significant correlations between time spent video-gaming and sleep and between video-gaming and sustained attention, but not working memory. Sleep duration, in turn, had a significant negative association with sustained attention performance. Mediation analyses revealed that the relationship between video-gaming and sustained attention was fully mediated by sleep duration. These results indicate that video-gaming affected the ability to sustain attention only in as much as it affected sleep. In order to minimise negative consequences of video-game playing, video-games should be used in moderation, avoiding use close to the sleep period, to obviate detriments to sleep and performance.

The impact of sleep on adolescent depressed mood, alertness and academic performance.

The present study developed and tested a theoretical model examining the inter-relationships among sleep duration, sleep quality, and circadian chronotype and their effect on alertness, depression, and academic performance. Participants were 385 adolescents aged 13-18 years (M = 15.6, SD = 1.0; 60% male) were recruited from eight socioeconomically diverse high schools in South Australia. Participants completed a battery of questionnaires during class time and recorded their sleep patterns in a sleep diary for 8 days. A good fit was found between the model and the data (χ(2)/df = 1.78, CFI = .99, RMSEA = .04). Circadian chronotype showed the largest association with on adolescent functioning, with more evening-typed students reporting worse sleep quality (ß = .50, p < .001) and diminished alertness (ß = .59, p < .001). Sleep quality was significantly associated with poor outcomes: adolescents with poorer sleep quality reported less sleep on school nights (ß = -.28, p < .001), diminished daytime alertness (ß = .33, p < .001), and more depressed mood (ß = .47, p < .001). Adolescents with poor sleep quality and/or more evening chronotype were also more likely to report worse grades, through the association with depression. Sleep duration showed no direct effect on adolescent functioning. These results identified the importance of two lesser-studied aspects of sleep: circadian chronotype and sleep quality. Easy-to-implement strategies to optimize sleep quality and maintain an adaptive circadian body clock may help to increase daytime alertness, elevate mood, and improve academic performance.

The sleep patterns and well-being of Australian adolescents.

AIM: Adolescent sleep patterns vary between countries, and these differences influence adolescent functioning and well-being. The present study provides data on the sleep and well-being of Australian adolescents. METHODS: 385 adolescents aged 13-18 years were recruited from 8 South Australian schools spanning the socio-economic spectrum. Adolescents completed survey battery during class time at school, followed by a 7-day sleep diary. RESULTS: Australian adolescents, on average, obtained inadequate sleep across the school week. Adolescents commonly reported difficulty initiating sleep, unrefreshing sleep, and the subjective feeling of restless legs. Problematic levels of sleepiness, fatigue, depressed mood and anxiety were highly prevalent. Later bedtimes, longer sleep onset latencies, and shorter sleep duration were significantly associated with aspects of poor daytime functioning. CONCLUSION: These results add to our knowledge of adolescent sleep and well-being worldwide. They also highlight the need for greater attention to sleep during this phase of development, when future behaviors and outcomes are being shaped.

Development of evening sleep homeostatic pressure in early adolescent boys.

The physiological processes governing sleep regulation show maturational changes during adolescent development. To date, data are available to specify when delays in circadian timing occur; however, no longitudinal data exist to characterize the maturation of the accumulation of sleep pressure across the evening. The aim of this longitudinal study was to test whether this change in evening sleep propensity can be identified during early adolescence. Twenty pre-pubescent boys' (Mage = 10.3, SD = 0.4 years) evening sleep homeostats were assessed using a series of sleep latency tests every hour (7:30 p.m. to 3:30 a.m.) at 6-month intervals across four waves. While results revealed shorter sleep onset latencies with increasing wakefulness (p < .001), this effect was not moderated by study wave (p = .79). Evening sleep propensity thus appears to remain stable in boys during early adolescence. Future studies should expand upon these findings by using larger samples of girls as well as boys across an extended age range during the teenage years.

The Chronic Sleep Reduction Questionnaire (CSRQ): a cross-cultural comparison and validation in Dutch and Australian adolescents.

Although adolescents often experience insufficient and/or poor sleep, sleep variables such as total sleep time do not account for individuals' sleep need and sleep debt and may therefore be an inadequate representation of adolescents' sleep problems and its daytime consequences. This problem can be overcome by using the Chronic Sleep Reduction Questionnaire (CSRQ), an assessment tool that measures symptoms of chronic sleep reduction and therefore accounting for sleep need and sleep debt. The present study aims at developing an English version of the CSRQ and assesses the reliability and validity of the Dutch and the English CSRQ version. The CSRQ was administered in large Dutch (n = 166, age = 15.2 ± 0.57 years, 28% male) and Australian (n = 236, age = 15.5 ± 0.99 years, 65% males) samples. Subjective sleep variables were measured with surveys and sleep diaries of five school nights. Additionally, sleep of the same five nights was monitored with actigraphy. Both CSRQ versions showed good psychometric properties concerning their reliability (Dutch: α = 0.85; English: α = 0.87) and validity as the same overall structure of the two CSRQ versions and significant correlations with subjective and objective sleep variables were found. School grades were related to chronic sleep reduction, whereas the relationship between grades and other sleep variables was weak or absent. These results highlight the idea that chronic sleep reduction may be a better indicator of adolescents' insufficient and/or poor sleep than other sleep variables such as total sleep time.

Low-intensity scheduled morning exercise for adolescents with a late chronotype: a novel treatment to advance circadian phase?

Study Objectives: During adolescence, an interplay between biological and environmental factors leads to constrained sleep duration and timing. The high prevalence of sleep deprivation during this developmental period is a public health concern, given the value of restorative sleep for mental, emotional, and physical health. One of the primary contributing factors is the normative delay of the circadian rhythm. Therefore, the present study aimed to evaluate the effect of a gradually advanced morning exercise schedule (30 min shift each day) completed for 45 min on 5 consecutive mornings, on the circadian phase and daytime functioning of adolescents with a late chronotype, compared with a sedentary control group. Methods: A total of 18 physically inactive male adolescents aged 15-18 years spent 6 nights at the sleep laboratory. The morning procedure included either 45 min walking on a treadmill or sedentary activities in dim light. Saliva dim light melatonin onset, evening sleepiness, and daytime functioning were assessed during the first and last night of laboratory attendance. Results: The morning exercise group had a significantly advanced (earlier) circadian phase (27.5 min ± 32.0), while sedentary activity resulted in a phase delay (-34.3 min ± 53.2). Morning exercise also led to higher evening sleepiness in the earlier hours of the night, but not at bedtime. Mood measures improved slightly in both study conditions. Conclusions: These findings highlight the phase-advancing effect of low-intensity morning exercise among this population. Future studies are needed to test the transference of these laboratory findings to adolescents' real life.

Sleep duration and mood in adolescents: an experimental study.

STUDY OBJECTIVES: This study examines the relationship between experimentally manipulated sleep duration and mood in adolescents. METHODS: Thirty-four adolescents (20 male), aged 15-17 years, lived in a sleep laboratory for 10 days and 9 nights. They were allocated to one of three sleep "doses" for five consecutive nights for 5, 7.5, or 10 h sleep opportunity per night. Two baseline nights and two recovery nights entailed 10 h sleep opportunity per night. Mood was measured every 3 h during wake using unipolar visual analogue scales measuring the mood states "depressed," "afraid," "angry," "confused," "anxious," "happy," and "energetic." RESULTS: Mixed models analyses with post hoc comparisons revealed that participants in the 5-h group, but not the 7.5- or 10-h groups, reported being significantly more depressed, angry, and confused during sleep restriction than at baseline. Adolescents were significantly less happy and energetic during sleep restricted to 5 h and significantly less energetic during sleep restricted to 7.5 h. When adolescents had 10 h sleep opportunities their happiness significantly increased. No statistically significant effects of sleep restriction were found for fear or anxiety, although small-to-moderate effects of sleep restricted to 5 or 7.5 h were found. Two nights of recovery sleep was not sufficient to recover from increased negative mood states for the 5-h group, although recovery occurred for positive mood states. CONCLUSIONS: Given the prevalence of insufficient sleep and the rising incidence of mood disorders and dysregulation in adolescents, these findings highlight the importance of sufficient sleep to mitigate these risks.

Homeostatic response to sleep restriction in adolescents.

The high prevalence of chronic sleep restriction in adolescents underscores the importance of understanding how adolescent sleep is regulated under such conditions. One component of sleep regulation is a homeostatic process: if sleep is restricted, then sleep intensity increases. Our knowledge of this process is primarily informed by total sleep deprivation studies and has been incorporated in mathematical models of human sleep regulation. Several animal studies, however, suggest that adaptation occurs in chronic sleep restriction conditions, showing an attenuated or even decreased homeostatic response. We investigated the homeostatic response of adolescents to different sleep opportunities. Thirty-four participants were allocated to one of three groups with 5, 7.5, or 10 h of sleep opportunity per night for five nights. Each group underwent a protocol of nine nights designed to mimic a school week between two weekends: two baseline nights (10 h sleep opportunity), five condition nights (5, 7.5, or 10 h), and two recovery nights (10 h). Measures of sleep homeostasis (slow-wave activity and slow-wave energy) were calculated from frontal and central EEG derivations and compared to predictions derived from simulations of the homeostatic process of the two-process model of sleep regulation. Only minor differences were found between empirical data and model predictions, indicating that sleep homeostasis is preserved under chronic sleep restriction in adolescents. These findings improve our understanding of effects of repetitive short sleep in adolescents.

The relationship between sleep duration and mood in adolescents: A systematic review and meta-analysis.

Insufficient sleep has been argued to result in deleterious changes to mood in adolescents and offers promise as a modifiable risk factor. A systematic review of the literature regarding sleep duration and mood in adolescents was conducted using the academic databases PsycINFO, PubMed, Medline, Scopus, and EMBASE to identify relevant literature. Seventy-four studies, including 361,505 adolescents were sourced out of the 1534 references identified, 73 of which were appropriate for meta-analysis. Pooled results indicated that less sleep was associated with a 55% increase in the likelihood of mood deficits. Positive mood showed the largest relationship with sleep duration, followed by anger, depression, negative affect and anxiety. Effect sizes also varied according to study design, how sleep was operationalised, and geographical region, but not according to the inclusion of covariates. Sleep duration has a significant negative impact on a range of mood states in healthy adolescents. These effects were witnessed across all geographical regions, highlighting that sleep is a universal and modifiable risk factor for preventing mood deficits in this at-risk population.

The roles of repetitive negative thinking and perfectionism in explaining the relationship between sleep onset difficulties and depressed mood in adolescents.

OBJECTIVE: The present study investigated the relationship between difficulty initiating sleep and depressed mood and whether it is mediated by repetitive negative thinking. A moderating role of perfectionism was also examined. METHODS: We surveyed 393 adolescents aged 14 to 20 years (M = 17.32, SD = 1.90) via an online questionnaire that assessed difficulty initiating sleep, repetitive negative thinking, perfectionism, and depressed mood. RESULTS: Results indicated that repetitive negative thinking fully mediated the relationship between difficulty initiating sleep and depressed mood. In addition, this relationship was moderated by perfectionism, specifically, the relationship between repetitive negative thinking and depressed mood was stronger among more perfectionistic adolescents. CONCLUSIONS: These findings highlight that repetitive negative thinking is significantly associated with both difficulty initiating sleep and depressed mood, supporting the conceptualization of repetitive negative thinking as a transdiagnostic process. Further, individual differences in perfectionism may amplify the relationship between repetitive negative thinking and mood. The role of repetitive negative thinking and perfectionism in explaining the link between sleep onset problems and depressed mood has important clinical implications through providing possible treatment targets.

Adolescent sleep restriction effects on cognition and mood.

Adolescents throughout the world do not obtain adequate sleep. A recent proliferation of experimental and quasi-experimental studies has considerably clarified the relationships between sleep loss and neurobehavioral function suggested by earlier epidemiological and cross-sectional studies. These new studies concur in finding that multiple successive nights of restricted sleep can impair multiple cognitive and affective functions. These effects cumulate from night to night, may not fully recover after weekend recovery sleep and may even be compounded by re-exposure to sleep restriction. An hour long afternoon nap reduces sleepiness in addition to improving vigilance, memory encoding and mood without interfering with nocturnal sleep when the latter is shortened. However, this does not detract from the point that adolescents require approximately 9h of sleep per night for optimal neurobehavioral function, a message that more need to embrace.

How internal and external cues for bedtime affect sleep and adaptive functioning in adolescents.

OBJECTIVE: To determine whether the main reason for bedtime is associated with sleep and adaptive functioning in adolescents. METHODS: Participants were 1374 adolescents (X age = 16.8 years, SD = 0.58; 33.6% male) from Helsinki, Finland. Adolescents completed a questionnaire battery including the Munich Chronotype Questionnaire, Strengths and Difficulties Questionnaire, Beck Depression Inventory, and items drawn from the School Sleep Habits Survey, and the Pittsburgh Sleep Quality Index. RESULTS: On school nights, adolescents whose parents set their bedtime, and those who went to bed when they were tired went to bed earlier, obtained more sleep and had earlier midpoint of sleep than adolescents who went to bed when they have finished messaging/socializing or when their television show had finished. Adolescents who went to bed when they had finished their homework had sleep that fell in between these groups. On weekends, adolescents whose parents set their bedtime went to bed earlier and had an earlier midpoint of sleep. However, there were no differences between groups in terms of sleep duration once the need to rise for school in the morning was removed. Adolescents who went to bed on school nights when they were tired or once their homework was finished had better adaptive functioning. CONCLUSIONS: These results provide support for two very different approaches to help optimize the sleep of adolescents: either by implementing parental regulation of bedtimes across adolescence, or by encouraging adolescents to use their bodily cues to indicate when it is time for bed, rather than relying on an external cue.

Sleep duration and risk-taking in adolescents: A systematic review and meta-analysis.

Risk-taking is associated with increased morbidity and mortality among adolescents, with insufficient sleep a potential factor contributing to heightened risk-taking propensity in this age group. A systematic review of the evidence examining the relationship between sleep duration and risk-taking in adolescents was conducted using PsycINFO, PubMed, Medline, Scopus, and CINAHL databases. These searches identified 26 studies including 579,380 participants, 24 of which were appropriate for meta-analysis. Pooled results indicated that insufficient sleep was associated with 1.43 [1.26, 1.62] times greater odds of risk-taking. This relationship was witnessed across diverse categories of risk-taking, including alcohol use, drug use, smoking, violent/delinquent behaviour, transport risk-taking/road safety, sexual risk-taking and trait risk-taking. Risk of bias analysis showed that the quality of the included studies was mixed. Further, few studies utilized either longitudinal or experimental designs, thus limiting causal conclusions. These findings highlight the importance of further research to examine the causal relationship between sleep duration and risk-taking and to elucidate the mechanisms that underpin this relationship.

An open trial of bedtime fading for sleep disturbances in preschool children: a parent group education approach.

STUDY OBJECTIVES: To evaluate the efficacy of bedtime fading to reduce sleep disturbances in preschool aged children by using a group parent education format. DESIGN: A repeated-measures design (pretreatment, treatment, post-treatment and two year follow-up). SETTING: Flinders University Child and Adolescent Sleep Clinic, Adelaide, South Australia. PARTICIPANTS: Participants comprised 21 children (M age = 3.0 ± 0.80 years, range = 1.5-4.0 years; 60% girls) identified as having difficulty initiating sleep, night waking, or a combination of both, and their mothers (M age = 36.1 ± 4.2 years). INTERVENTIONS: Mothers attended two group sessions that included basic sleep education (sleep needs, sleep architecture, and sleep homeostasis) and bedtime fading instruction. MEASUREMENTS AND RESULTS: Primary outcome variables were sleep onset latency (SOL), wake after sleep onset (WASO), and bedtime tantrums, and these variables were measured using two week maternal report sleep diaries. Immediate improvements were observed over pretreatment to treatment in average SOL per night (M = 23.2 ± 11.3 min vs. M = 13.0 ± 7.3 min, d = 0.91), average WASO per night (M = 32.4 ± 23.1 min vs. M = 24.0 ± 18.3 min, d = 0.41), and number of bedtime tantrums per week (M = 1.7 ± 3.0 vs. M = 0.4 ± 0.7, d = 0.43). Treatment gains were maintained at two year follow-up. Mothers rated bedtime fading high in terms of usefulness and satisfaction, and they reported that could successfully reimplement the treatment when needed. CONCLUSIONS: Bedtime fading is a brief and promising intervention for pre-schoolers' sleep difficulties. This simple intervention can be easily implemented by parents at home with little instructions, resulting in improvements in sleep and bedtime tantrums.

Sleep spindles in adolescence: a comparison across sleep restriction and sleep extension.

BACKGROUND: The tendency for adolescents to have restricted sleep has been examined in numerous studies; however, the impact of sleep restriction on adolescents' neural activity during sleep (measured by electroencephalography (EEG)) is less extensively researched, particularly regarding sleep spindles. METHODS: In this experimental study, 34 adolescents attended a 10-day laboratory study where they received five consecutive nights of either 5 h, 7.5 h or 10 h of sleep opportunity, with one adaptation, one baseline and two recovery nights of 10 h of sleep opportunity before and after the experimental phase. RESULTS: Both within- and between-subjects effects were observed for fast sleep spindle characteristics of density, duration and amplitude. Overall, when experiencing severe sleep restriction, fast spindles in adolescents were lower in amplitude and longer in duration. Sex differences were also seen for fast spindle amplitude. CONCLUSIONS: This investigation adds to the knowledge in this field by investigating specific sleep spindle characteristics in the context of experimentally manipulated sleep. Sleep restriction is highly prevalent among adolescents. These findings indicate that chronic sleep restriction has an impact on brain activity related to sleep spindles.

Estimating adolescent sleep need using dose-response modeling.

Study Objectives: This study will (1) estimate the nightly sleep need of human adolescents, (2) determine the time course and severity of sleep-related deficits when sleep is reduced below this optimal quantity, and (3) determine whether sleep restriction perturbs the circadian system as well as the sleep homeostat. Methods: Thirty-four adolescents aged 15 to 17 years spent 10 days and nine nights in the sleep laboratory. Between two baseline nights and two recovery nights with 10 hours' time in bed (TIB) per night, participants experienced either severe sleep restriction (5-hour TIB), moderate sleep restriction (7.5-hour TIB), or no sleep restriction (10-hour TIB) for five nights. A 10-minute psychomotor vigilance task (PVT; lapse = response after 500 ms) and the Karolinska Sleepiness Scale were administered every 3 hours during wake. Salivary dim-light melatonin onset was calculated at baseline and after four nights of each sleep dose to estimate circadian phase. Results: Dose-dependent deficits to sleep duration, circadian phase timing, lapses of attention, and subjective sleepiness occurred. Less TIB resulted in less sleep, more lapses of attention, greater subjective sleepiness, and larger circadian phase delays. Sleep need estimated from 10-hour TIB sleep opportunities was approximately 9 hours, while modeling PVT lapse data suggested that 9.35 hours of sleep is needed to maintain optimal sustained attention performance. Conclusions: Sleep restriction perturbs homeostatic and circadian systems, leading to dose-dependent deficits to sustained attention and sleepiness. Adolescents require more sleep for optimal functioning than typically obtained.