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

Neurobehavioral functions during recurrent periods of sleep restriction: effects of intra-individual variability in sleep duration

STUDY OBJECTIVES

To investigate whether neurobehavioral impairments are exacerbated during successive cycles of sleep restriction and recovery in young adults, and whether a variable short sleep schedule can mitigate these impairments relative to a stable one.

METHODS

Fifty-two healthy young adults (25 males, aged: 21-28) were randomly assigned to the stable short sleep group, the variable short sleep group, or the control group in this laboratory-based study. They underwent two baseline nights of 8-hour time-in-bed (TIB), followed by two cycles of "weekday" sleep opportunity manipulation and "weekend" recovery (8-hour TIB). During each manipulation period, the stable short sleep and the control groups received 6- and 8-hour TIBs each night respectively, while the variable short sleep group received 8-hour, 4-hour, 8-hour, 4-hour, and 6-hour TIBs from the first to the fifth night. Neurobehavioral functions were assessed five times each day.

RESULTS

The stable short sleep group showed faster vigilance deterioration in the second week of sleep restriction as compared to the first. This effect was not observed in the variable short sleep group. Subjective alertness and practice-based improvement in processing speed were attenuated in both short sleep groups.

CONCLUSIONS

In young adults, more variable short sleep schedules incorporating days of prophylactic or recovery sleep might mitigate compounding vigilance deficits resulting from recurrent cycles of sleep restriction. However, processing speed and subjective sleepiness were still impaired in both short sleep schedules. Getting sufficient sleep consistently is the only way to ensure optimal neurobehavioral functioning.

CLINICAL TRIAL

Performance, Mood, and Brain and Metabolic Functions During Different Sleep Schedules (STAVAR), https://www.clinicaltrials.gov/study/NCT04731662, NCT04731662.

The Impact of Delayed School Start Times During COVID-19 on Academic Performance: A Longitudinal Naturalistic Study in Italian High Schools

Background

Delaying school start times has been proposed as a potential solution to address chronic sleep curtailment among adolescents and its negative consequences on their physical and mental well-being. This study investigates the impact of delayed school start times due to the COVID-19 pandemic on academic achievement.

Subjects and Methods

Two separate observational studies were conducted involving high school students from the first/second year (n=232) (Study 1) and from the final year (n=39) (Study 2). Multivariate Analyses of Covariance were performed to assess for statistical differences in academic performance (ie, global, humanistic, and scientific performance) and absenteeism (ie, number of school absences). Two main factors were considered: "school start time" (ie, standard-8:00 AM vs late-9:40 AM) and "time interval" (ie, first academic semester vs second academic semester), controlling for the school year (Study 1) and circadian preference (Study 2).

Results

Delaying school start times was positively associated with better academic performance in scientific subjects among first/second-year students (F1,229=6.083, p=0.026) and global academic performance among last-year students (F1,35=4.522, p=0.041). Furthermore, first/second-year students significantly increased their school achievement (F1,229>29.423, p<0.001) and school absences (F1,229=66.160, p<0.001) during the second semester of the academic year. No significant effect of "school start time" on school attendance was observed. Additionally, circadian preference was found to be a significant covariate among last-year students, with early chronotypes exhibiting better academic performance (r>0.369, p<0.025).

Conclusion

These findings confirm past evidence about the beneficial effects of delayed school start times on academic outcomes, with the additional advantage of observing them within a natural context that emerged during the pandemic. Further research is needed to explore the phenomenon more systematically and take into account the broader implications of implementing this change.

A bibliometric analysis of insomnia in adolescent

Background

The negative effects of insomnia on adolescents' development, academic performance, and quality of life place a burden on families, schools, and society. As one of the most important research directions for insomnia, adolescent insomnia has significant research value, social value, and practical significance. Unfortunately, there is no bibliometric analysis in this field of study. This study aims to analyze published articles using bibliometrics, summarize the current research progress and hot topics in this field systematically and exhaustively, and predict the future direction and trend of research.

Methods

For this study, the Web of Science Core Collection (WoSCC) database was searched between 2002 and 2022 for publications related to adolescent insomnia. The R-bibliometrix, VOSViewer, and CiteSpace software were utilized for bibliometric analysis.

Results

This investigation included 2468 publications from 3102 institutions in 87 countries, led by China and the United States. This field of research has entered a period of rapid development since 2017. The journal with the most publications on adolescent insomnia is Sleep, which is also the most co-cited journal. American Journal of Psychology has the highest impact factor among the top 10 journals. These papers were written by 10605 authors; notably, Liu Xianchen emerged as the author with the highest frequency of publications, while Mary A. Carskadon was the most frequently co-cited author. Mental health and comorbid diseases were the main research directions in this field. "Depression," "anxiety," "mental health," "COVID-19," "stress," "quality of life," "heart rate variability," and "attention-deficit hyperactivity disorder" were hot spots and trends in this field at the current moment.

Conclusion

The research on adolescent insomnia has social value, research value, and research potential; its development is accelerating, and an increasing number of researchers are focusing on it. This study summarized and analyzed the development process, hot spots, and trends of adolescent insomnia research using bibliometric analysis, which identified the current hot topics in this field and predicted the development trend for the future.

Sleep Architecture and EEG Power Spectrum Following Cumulative Sleep Restriction: A Comparison between Typically Developing Children and Children with ADHD

No studies have looked at the effects of cumulative sleep restriction (CSR) on sleep architecture or the power spectrum of sleep EEG (electroencephalogram) in school-age children, as recorded by PSG (polysomnography). This is true for both typically developing (TD) children and children with ADHD (attention deficit/hyperactivity disorder), who are known to have more sleep difficulties. Participants were children (ages 6-12 years), including 18 TD and 18 ADHD, who were age- and sex-matched. The CSR protocol included a two-week baseline and two randomized conditions: Typical (six nights of sleep based on baseline sleep schedules) and Restricted (one-hour reduction of baseline time in bed). This resulted in an average of 28 min per night difference in sleep. Based on ANOVAs (analysis of variance), children with ADHD took longer to reach N3 (non-rapid eye movement), had more WASO (wake after sleep onset) (within the first 5.1 h of the night), and had more REM (rapid eye movement) sleep than TD children regardless of condition. During CSR, ADHD participants had less REM and a trend toward longer durations of N1 and N2 compared to the TD group. No significant differences in the power spectrum were found between groups or conditions. In conclusion, this CSR protocol impacted some physiological aspects of sleep but may not be sufficient to cause changes in the power spectrum of sleep EEG. Although preliminary, group-by-condition interactions suggest that the homeostatic processes in children with ADHD may be impaired during CSR.

Adolescent sleep, distress, and technology use: weekday versus weekend

BACKGROUND

In adolescents, technology use at bedtime is linked to disrupted sleep and psychological distress. Adolescents are known to sleep later on weekends compared to weekdays but whether this leads to greater technology use, and, hence, additional psychological distress is not known. At greater risk maybe adolescents with a late compared to early chronotype, that is a preference for late versus early sleep onset and offset times.

METHOD

Self-reported measures of sleep timing, chronotype (early, neither early nor late, late), technology medium (social media/texting, TV/streaming, and gaming), and psychological distress (DASS-21) were collected from 462 students attending one Australian high school.

RESULTS

Technology use at bedtime was greater on weekends and especially in adolescents with a late chronotype. Social media/texting on weekends was predictive of delayed sleep onset times (β = .120), and shorter sleep (β = -.172). Shorter sleep on weekdays but not on weekends was associated with greater psychological distress. Technology medium and chronotype were not predictive of psychological distress.

CONCLUSIONS

This study confirmed that technology use and its impact on sleep differed on weekdays compared to weekends and that a late chronotype was associated with greater technology use. However, neither technology medium nor chronotype was found to affect psychological distress. While greater autonomy may be granted to adolescents over the weekend regarding sleep behaviour, young people, parents, and clinicians should be mindful of the link between technology use and sleep.

Staying vigilant during recurrent sleep restriction: dose-response effects of time-in-bed and benefits of daytime napping

Study Objectives

We characterized vigilance deterioration with increasing time-on-task (ToT) during recurrent sleep restriction of different extents on simulated weekdays and recovery sleep on weekends, and tested the effectiveness of afternoon napping in ameliorating ToT-related deficits.

Methods

In the Need for Sleep studies, 194 adolescents (age = 15–19 years) underwent two baseline nights of 9-h time-in-bed (TIB), followed by two cycles of weekday manipulation nights and weekend recovery nights (9-h TIB). They were allocated 9 h, 8 h, 6.5 h, or 5 h of TIB for nocturnal sleep on weekdays. Three additional groups with 5 h or 6.5 h TIB were given an afternoon nap opportunity (5 h + 1 h, 5 h + 1.5 h, and 6.5 h + 1.5 h). ToT effects were quantified by performance change from the first 2 min to the last 2 min in a 10-min Psychomotor Vigilance Task administered daily.

Results

The 9 h and the 8 h groups showed comparable ToT effects that remained at baseline levels throughout the protocol. ToT-related deficits were greater among the 5 h and the 6.5 h groups, increased prominently in the second week of sleep restriction despite partial recuperation during the intervening recovery period and diverged between these two groups from the fifth sleep-restricted night. Daytime napping attenuated ToT effects when nocturnal sleep restriction was severe (i.e. 5-h TIB/night), and held steady at baseline levels for a milder dose of nocturnal sleep restriction when total TIB across 24 h was within the age-specific recommended sleep duration (i.e. 6.5 h + 1.5 h).

Conclusions

Reducing TIB beyond the recommended duration significantly increases ToT-associated vigilance impairment, particularly during recurrent periods of sleep restriction. Daytime napping is effective in ameliorating such decrement.

Clinical Trial Registration

NCT02838095, NCT03333512, and NCT04044885.

Sleep Patterns and Myopia Among School-Aged Children in Singapore

Purpose

To evaluate the associations of sleep factors with myopia, spherical equivalent (SE), and axial length (AL) in elementary school-aged children from the Growing Up in Singapore Towards healthy Outcomes (GUSTO) birth cohort.

Methods

This cross-sectional study included multi-ethnic children who participated in the GUSTO prospective birth cohort and were delivered in two major tertiary hospitals in Singapore (2009–2010). Sleep factors and myopia outcomes were assessed at the 8- and 9-year study visits, respectively. Parent-reported sleep quality was assessed with the Children's Sleep Habits Questionnaire (CSHQ) total scores. Additionally, each child's sleep duration, timing (bedtime; waketime), and the consistency of sleep duration or timing (i.e., the difference between weekends and weekdays) were parent-reported. Outcomes included cycloplegic SE, myopia (SE ≤ −0.5 D) and AL. Eye measurements from both eyes were included in the analyses. Multivariable linear or logistic regression with Generalized Estimating Equations were used to account for the correlation between paired eyes and confounders in the associations of sleep factors at age 8 and myopia at age 9.

Results

A total of 572 multi-ethnic children (49.5% boys; 56.1% Chinese) aged 9 years were included in the analyses. Overall, 37.3% of eyes were myopic. Children reported a mean total CSHQ score of 46 [standard deviation (SD) = 6]. The mean duration of sleep was 9.2 (SD = 1.0) hours per day (h/day), with 59.9% of children reporting sufficient sleep (≥9 h/day) based on guidelines recommended by the National Sleep Foundation, USA. The mean bedtime and wake time were 22:00 (SD = 00:53) and 07:08 (SD = 00:55), respectively. In multivariable regression models, total CSHQ scores, the duration of sleep, bedtime and wake time were not significantly associated with myopia, SE, or AL (p ≥ 0.05 for all), adjusting for gender, ethnicity, time outdoors, near-work, parental myopia, maternal education levels (and additionally the child's height when the outcome was AL). Similarly, the consistency of both the duration and timing of sleep (across weekends and weekdays) were not significantly associated with myopia, SE, or AL (p ≥ 0.05 for all).

Conclusion

In this cross-sectional study, sleep quality, duration, timing, and the consistency of specific sleep factors were not independently associated with myopia, SE, or AL among elementary school-aged children in Singapore. Large longitudinal studies are warranted to corroborate these results.

A Comprehensive Review of the Literature on Sleep Difficulties and Suicidality in Youth to Inform an Integrative Developmental Model and Future Directions

Purpose of Review

Suicide is currently the second leading cause of death among youth. Identification of modifiable near-term risk factors can inform suicide prevention strategies. One promising, readily assessed factor is sleep. We critically review the literature on sleep and suicidal thoughts and behaviors among youth.

Recent Findings

Most studies examining the youth sleep-suicidality relationship are from epidemiological samples in which both sleep problems and suicidality were assessed over variable timeframes using limited items from scales not designed to measure these constructs. Nonetheless, these data overwhelmingly support an association between suicidality and a range of sleep difficulties (e.g., insomnia, short/long sleep, weekend oversleep), above and beyond depressive symptoms. Limited studies include clinical samples or prospective designs. We review potential mechanisms and present a developmentally-informed integrative model.

Summary

Literature supports a clear association between sleep difficulties and youth suicidality. Future directions include prospective longitudinal studies and targeted prevention efforts.

The Impact of Weekday-to-Weekend Sleep Differences on Health Outcomes among Adolescent Students

The sleep difference between weekdays and weekends can lead to negative physical and mental health outcomes in adolescents. Thus, this study has attempted to analyze the impact of sleep time differences on various health outcomes, using nationally representative panel data. Data from the junior high school student panel of the Korean Children and Youth Panel Survey were analyzed. The sleep difference was defined as the difference between the average sleep duration on weekdays and that on weekends in minutes. A series of mixed effect linear regression models for continuous variables or mixed effect logit regression for binary variables was utilized. Korean adolescent students reported from 96.8 min to 133.2 min of sleep duration difference between weekdays and weekends. After controlling for gender, parent work status, and type of housing, the weekday-to-weekend sleep differences were associated with various health-related outcomes including concentration difficulty, aggression, somatic symptoms, and withdrawal. Additionally, adolescent student life satisfaction was associated with sleep difference. The sleep differences among adolescent students were more associated with mental health-related outcomes and emotional symptoms than with physical health-related outcomes. The appropriate intervention to reduce the sleep difference gap is an important key to improve health in the adolescence period.

Alcohol use severity and the neural correlates of the effects of sleep disturbance on sustained visual attention

Alcohol misuse is associated with sleep disturbance and cognitive dysfunction. However, the neural processes inter-relating the severity of alcohol use, sleep disturbance and cognitive performance remain under-investigated. We addressed this issue with a dataset of 964 subjects (504 women) curated from the Human Connectome Project. Participants were assessed with the Pittsburgh Sleep Quality Index (PSQI) and fMRI while identifying relational dimension pictures and matching dimension pictures (as a control) in alternating blocks. Imaging data were analyzed with published routines and the results were evaluated at a corrected threshold. Subjects showed lower accuracy rate and longer reaction time (RT) in relational than control blocks. The difference in RT between the two blocks (RT_Rel-Con) was driven primarily by the RT and correlated positively with performance accuracy of relational trials, suggesting that a more cautious response (i.e., longer RT_Rel-Con) improved accuracy. The severity of alcohol use, identified from principal component analysis of drinking metrics, was positively correlated with sleep disturbance. Further, whole-brain regression identified activity of the superior colliculus (SC) during relational vs. control blocks in positive and negative correlation with RT_Rel-Con and PSQI score, respectively. Mediation and path analyses demonstrated a significant model: more severe alcohol use → greater sleep disturbance → diminished SC activity → impaired performance. These findings support the influences of alcohol misuse on sleep and suggest neural correlates that mediate the relationship between sleep disturbance and altered sustained attention in young adults.

Weekly and seasonal variation in the circadian melatonin rhythm in humans: Entrained to local clock time, social time, light exposure or sun time?

A recent elegant study published in this journal (Zerbini, Winnebeck & Merrow, J Pineal Res, e12723, 2021) reported data on weekly and seasonal changes in circadian timing, as assessed by the melatonin rhythm in dim light in a population that was exposed to a change from standard time to day light saving time. The authors highlight a one hour earlier timing of melatonin onset in summer compared with winter and a 20 minutes delay on work-free days compared with work days. The variations in the timing of the melatonin rhythm are reported in standard time and the authors imply that the data are consistent with synchronization to midday and that "we know that humans entrain to sun time." Here, we show that their extensive data are most parsimoniously explained by entrainment to local clock time and associated light exposure rather than "sun time," indexed by either dawn or midday.

Relationships between Depression, Daily Physical Activity, Physical Fitness, and Daytime Sleepiness among Japanese University Students

In Japan and other developed countries, the lifestyles of many—particularly the younger generation—have been disrupted in recent years. This disruption may manifest as a decrease in physical activity and deterioration in the quality and quantity of sleep. Depressive tendencies are also increasing among university students. This study examined the relationship between mental health, physical activity, physical fitness, and daytime sleepiness. Eighty-five undergraduate students participated in this study (52 men and 33 women, aged 18.9 (±1.4) years). Physical activity levels were measured using an accelerometer (Lifecorder, Kenz, Nagoya, Japan) for two weeks. To evaluate their level of physical fitness, maximal oxygen uptake (V˙O₂max) was calculated by an indirect method using a cycle ergometer. Depressive tendencies and daytime sleepiness were evaluated using the Patient Health Questionnaire (PHQ-9). The PHQ-9 score was positively correlated with sleepiness (r = 0.35, p = 0.001) and total steps per day (r = 0.39, p < 0.001). Moreover, the PHQ-9 score was positively correlated with V˙O₂max (r = 0.25, p = 0.019). The PHQ-9 score was higher in students with good exercise habits or part-time jobs. An important finding was the positive correlation between depression and variables related to physical activity levels. These results suggest that vigorous physical activity, such as exercise and part-time jobs, might be positively associated with depressive tendencies among university students.

Sleep timing and consistency are associated with the standardised test performance of Icelandic adolescents

Sleep has been shown to affect cognitive function in laboratory studies; however, its association to the academic performance of adolescents has largely been demonstrated using self-reported measures. Studies with objective measures of both sleep and academic performance are limited. The aim of the present study was to determine whether the free-living sleep quantity, quality, and timing of 15-year-old adolescents measured with wrist actiography are associated with their scores on national standardised examinations as an objective measure of academic achievement. We measured sleep with wrist actiography for 1 week in 253 (150 girls) Icelandic adolescents with a mean (SD) age of 15.9 (0.3) years. Multiple linear regression was used to assess associations between sleep parameters and combined standardised examination scores in mathematics, English, and Icelandic obtained from the Icelandic Directorate of Education. We found that students went to bed at 00:49 hours (± 51.8 min) and slept for a mean (SD) of 6.6 (0.7) hr/night, with a median (interquartile range) night-to-night variation in sleep duration of 1.2 (0.7) hr and an efficiency of 88.1 (5.3)%. Combined analyses adjusted for sex, demonstrated that both bedtime and night-to-night variability in total sleep time were negatively associated with the average score across all topics. Sex-specific associations did not indicate clear differences between boys and girls. These findings suggest that, in addition to appropriate sleep duration, public health guidance should also highlight the importance of early and consistent sleep schedules to academic achievement for both boys and girls.

Sleepiness is a signal to go to bed: data and model simulations

Study Objectives

Assess the validity of a subjective measure of sleepiness as an indicator of sleep drive by quantifying associations between intraindividual variation in evening sleepiness and bedtime, sleep duration, and next morning and subsequent evening sleepiness, in young adults.

Methods

Sleep timing and sleepiness were assessed in 19 students in late autumn and late spring on a total of 771 days. Karolinska Sleepiness Scales (KSS) were completed at half-hourly intervals at fixed clock times starting 4 h prior to participants’ habitual bedtime, and in the morning. Associations between sleepiness and sleep timing were evaluated by mixed model and nonparametric approaches and simulated with a mathematical model for the homeostatic and circadian regulation of sleepiness.

Results

Intraindividual variation in evening sleepiness was very large, covering four or five points on the 9-point KSS scale, and was significantly associated with subsequent sleep timing. On average, a one point higher KSS value was followed by 20 min earlier bedtime, which led to 11 min longer sleep, which correlated with lower sleepiness next morning and the following evening. Associations between sleepiness and sleep timing were stronger in early compared to late sleepers. Model simulations indicated that the directions of associations between sleepiness and sleep timing are in accordance with their homeostatic and circadian regulation, even though much of the variance in evening sleepiness and details of its time course remain unexplained by the model.

Conclusion

Subjective sleepiness is a valid indicator of the drive for sleep which, if acted upon, can reduce insufficient sleep.

Sleep pattern and staging in elite adolescent rugby players during the in-season competitive phase compared to an age matched non-athlete population

Young athletes must contend with the constraints of elite sports on top of school commitments and the physiological processes associated with adolescence. This study assessed week and weekend sleep and schedule of activities in elite adolescent rugby players during the in-season competitive phase compared with age-matched non-athlete controls. 32 adolescents (GR: 16 elite rugby players, GC: 16 controls) from the same boarding school filled out a daily schedule of activities and a sleep diary, and wore a multichannel electroencephalogram for 14 days. They later filled out questionnaires on their sleep quality, sleepiness, and perceived stress. Both groups showed insufficient sleep duration during the week (<7 h). Only GC caught up on their sleep debt during the weekend (increased TIB, TST and time spent in REM sleep, all p < 0.001). Weekend TIB, TST and, N3 sleep remained similar to that for weekdays in GR. However, GR experienced lower sleep quality (decreased SE, increased WASO, all p < 0.01) and a decrease in REM sleep (p < 0.01). Schedules of activities showed an increase in time spent on overall activities during the weekend, mainly due to competition and sport-specific travel, which resulted in a decrease in sleep opportunity time compared with GC (p < 0.001). Δ sleep opportunity time (weekend-week) was associated with Δ TST (weekend-week), and Δ TST (weekend-week) was associated with sleepiness and perceived stress. Busy schedules during the competitive season decreased sleep opportunity time and prevented elite adolescent rugby players from catching up on their sleep at weekends.HIGHLIGHTS Adolescent rugby players have insufficient sleep during both week and weekend of the in-season competitive phaseCongested schedule prevented elite adolescent rugby players from catching up on their sleep at weekends.Sleep considerations are necessary when planning the weekend sporting schedules.

Neurobehavioural functions during variable and stable short sleep schedules

We investigated whether variable sleep schedules might mitigate the neurobehavioural deficits induced by multiple nights of sleep restriction. In this 4-night experiment, 78 young adults (age: 18-28 years) were randomly assigned to four groups: 8888, 8666, 8846 and 8486, where each digit corresponded to time-in-bed in hours for each study night. After one baseline night of 8-hr time-in-bed, time-in-bed remained unchanged for the 8888 group, while the other groups had short sleep schedules (total time-in-bed = 18 hr) that differed in the number of time-in-bed changes. Sleep was monitored using actigraphy at home. Daytime neurobehavioural functions were assessed in the laboratory at single time points, after the baseline night, and again after 3 nights of the sleep manipulation period. For sustained attention, the 8888 group responded faster in the Psychomotor Vigilance Task after the manipulation period (p = .01), while responses became slower for the less variable sleep schedules (8666 and 8846; p < .01), but not the most variable sleep schedule (8486; p = .14). Processing speed also improved in the 8888 group and the variable 8846 and 8486 groups (p < .01), but not in the stable 8666 group (p = .09). Furthermore, subjective sleepiness was preserved in the 8888 and, importantly, 8486 groups (p > .05), but was elevated in the 8666 and 8846 groups (p < .05). These findings suggest that when sleep opportunities are limited across multiple nights, a variable sleep schedule that allows for prophylactic and/or recovery sleep on some nights may mitigate some daytime neurobehavioural deficits as compared with a schedule with no opportunity for recovery.

The acute effects of sleep restriction therapy for insomnia on circadian timing and vigilance

Sleep-restriction therapy (SRT) has been shown to improve insomnia symptoms by restricting sleep opportunity. Curtailment of time in bed affects the duration and consolidation of sleep, but also its timing. While recent work suggests that people with insomnia are characterised by misalignment between circadian and behavioural timing of sleep, no study has investigated if SRT modifies this relationship. The primary aim of the present study was to examine change in phase angle after 2 weeks of SRT. As a secondary aim, we also sought to assess the effect of SRT on psychomotor vigilance. Following a 1-week baseline phase, participants implemented SRT for 2 consecutive weeks. Phase angle was derived from the difference between the decimal clock time of dim light melatonin onset (DLMO) and attempted sleep time. Secondary outcomes included vigilance (assessed via hourly measurement during the DLMO laboratory protocol), sleep continuity (assessed via sleep diary and actigraphy), and insomnia severity. Eighteen participants meeting insomnia criteria (mean [SD] age 37.06 [8.99] years) took part in the study. Consistent with previous research, participants showed robust improvements in subjective and objective sleep continuity, as well as reductions in insomnia severity. The primary outcome (phase angle) was measurable in 15 participants and revealed an increase of 34.8 min (~0.58 hr; 95% confidence interval [CI] 0.01-1.15) from baseline to post-treatment (mean [SD] 2.27 [0.94] versus 2.85 [1.25] hr). DLMO remained relatively stable (20:49 versus 21:01 hours), while attempted sleep was 46.8 min later (~0.78 hr; 95%CI 0.41-1.15; 23:05 versus 23:52 hours). For psychomotor vigilance, reaction time was delayed (by 52.71 ms, 95% CI 34.44-70.97) and number of lapses increased (by 5.84, 95% CI 3.93-7.75) after SRT. We show that SRT increases phase angle during treatment, principally by delaying the timing of sleep attempt. Future studies are needed to test if an increase in phase angle is linked to clinical improvement. Finally, reduction in vigilance after SRT appears to be of similar magnitude to normal sleepers undergoing experimental sleep restriction, reinforcing the importance of appropriate safety advice during implementation.

Wide awake at bedtime? Effects of caffeine on sleep and circadian timing in male adolescents - A randomized crossover trial

Adolescents often suffer from short and mistimed sleep. To counteract the resulting daytime sleepiness they frequently consume caffeine. However, caffeine intake may exaggerate sleep problems by disturbing sleep and circadian timing. In a 28-hour double-blind randomized crossover study, we investigated to what extent caffeine disturbs slow-wave sleep (SWS) and delays circadian timing in teenagers. Following a 6-day ambulatory phase of caffeine abstinence and fixed sleep-wake cycles, 18 male teenagers (14-17 years old) ingested 80 mg caffeine vs. placebo in the laboratory four hours prior to an electro-encephalographically (EEG) recorded nighttime sleep episode. Data were analyzed using both frequentist and Bayesian statistics. The analyses suggest that subjective sleepiness is reduced after caffeine compared to placebo. However, we did not observe a strong caffeine-induced reduction in subjective sleep quality or SWS, but rather a high inter-individual variability in caffeine-induced SWS changes. Exploratory analyses suggest that particularly those individuals with a higher level of SWS during placebo reduced SWS in response to caffeine. Regarding salivary melatonin onsets, caffeine-induced delays were not evident at group level, and only observed in participants exposed to a higher caffeine dose relative to individual bodyweight (i.e., a dose > 1.3 mg/kg). Together, the results suggest that 80 mg caffeine are sufficient to induce alertness at a subjective level. However, particularly teenagers with a strong need for deep sleep might pay for these subjective benefits by a loss of SWS during the night. Thus, caffeine-induced sleep-disruptions might change along with the maturation of sleep need.

Association between free-living sleep and memory and attention in healthy adolescents

In laboratory studies, imposed sleep restriction consistently reduces cognitive performance. However, the association between objectively measured, free-living sleep and cognitive function has not been studied in older adolescents. To address this gap, we measured one week of sleep with a wrist-worn GT3X+ actigraph in 160 adolescents (96 girls, 17.7 ± 0.3 years) followed by assessment of working memory with an n-back task and visual attention with a Posner cue-target task. Over the week, participants spent 7.1 ± 0.8 h/night in bed and slept 6.2 ± 0.8 h/night with 88.5 ± 4.8% efficiency and considerable intra-participant night-to-night variation, with a standard deviation in sleep duration of 1.2 ± 0.7 h. Sleep measures the night before cognitive testing were similar to weekly averages. Time in bed the night before cognitive testing was negatively associated with response times during the most challenging memory task (3-back; p = 0.005). However, sleep measures the night before did not correlate with performance on the attention task and weekly sleep parameters were not associated with either cognitive task. Our data suggests shorter acute free-living sleep may negatively impact difficult memory tasks, however the relationship between free-living sleep and cognitive task performance in healthy adolescents is less clear than that of laboratory findings, perhaps due to high night-to-night sleep variation.

Sleep problems and suicide risk in youth: A systematic review, developmental framework, and implications for hospital treatment

OBJECTIVE

Sleep problems are transdiagnostic symptoms that confer significant risk for suicidal thoughts and behaviors (STBs) in adults. However, less is known about the sleep-STB association in adolescence-a developmental period when rates of STBs increase drastically, and sleep problems may be particularly pernicious. This article provides a systematic review of research on the sleep-STB association in youth, an overview of changes in sleep regulation during adolescence that may make sleep problems particularly detrimental for youth, and a discussion of the clinical implications of the sleep-STB association for hospitalized youth.

METHOD

The systematic review included all longitudinal studies in which sleep problems were examined as prospective predictors of STBs in adolescents (aged 10-24 years). The search was conducted on December 1, 2017 using PsychINFO, PubMed, and Web of Science databases.

RESULTS

Ten studies qualified for inclusion in this review. Of these, seven studies found at least one type of sleep problem significantly predicted a STB outcome.

CONCLUSIONS

Although findings are mixed, growing research suggests that sleep problems may be a unique risk factor for STBs in youth. Sleep problems may be particularly important intervention target because they are easily assessed across healthcare settings and are amenable to treatment.

The Relationship Between Sleep Duration and Participation in Home, School, and Community Activities Among School-Aged Children

Sleep duration has important implications for children’s participation in daily activities; however, past attempts to examine this relationship has been limited to specific types of physical or educational activities. The present study aimed to investigate the relationship between sleep duration and participation in various daily activities among school-aged children. A school-based sample of 391 children aged 5–12 years (boys: 52.4%) participated in this cross-sectional survey. Sleep duration was quantified using parental reports of their children’s bedtime and wake-up time on weekdays and weekends. The parent-reported Participation and Environment Measure for Children and Youth was used to measure their children’s participation frequency and involvement in 25 home, school, and community activities. The results of hierarchical regression analyses showed that, when the demographic variables were controlled for, weekday sleep duration was positively related to homework involvement and negatively related to the frequency of TV viewing; however, it was unrelated to participation in school and community activities. Conversely, weekend sleep duration was positively related to overall participation in school activities, and participation frequency and involvement in some home and community activities. Furthermore, sleep duration was approximately an hour shorter on weekdays than on weekends. These results suggest that weekend sleep duration has stronger positive implications for children’s participation in daily activities than does weekday sleep duration. Interventions aiming to promote children’s activity participation may either prolong children’s weekend sleep duration or address their shorter weekday sleep duration.

Napping Behaviors and Extracurricular Club Activities in Japanese High School Students: Associations with Daytime Sleep Problems

Although engaging in evening naps and extracurricular activities are popular among Japanese high school students, the associations between these behaviors and daytime sleep problems were unclear. A questionnaire on daily life and sleeping habits was administered to 1314 high school students, aged between 15–17 years. The respondents were categorized by their after-school napping habits (did not nap, napped 1–2 days/week, napped ≥3 days/week), and their extracurricular activities (no activity, cultural club, athletic club). The mean nocturnal sleep duration on weekdays (± standard deviation (SD)) was 390 ± 56 min. This was significantly shorter in those students with a higher number of days/week spent napping (p < 0.001), and slightly longer for those in the athletic club (p < 0.001). Sleep problems—including subjective insufficient sleep, excessive sleepiness during class ≥3 days/week, and falling asleep during class ≥3 days/week—were reported by 64%, 55%, and 33% of respondents, respectively. A multiple logistic regression analysis showed significantly higher risks for excessive sleepiness among students taking naps ≥3 days/week, and who belonged to athletic clubs. In addition to those factors, students in cultural clubs revealed significantly higher risks for falling asleep during classes. Future studies are required to decrease daytime sleep problems associated with evening naps and extracurricular activities among high school students.

Altering Adolescents' Pre-Bedtime Phone Use to Achieve Better Sleep Health

Mobile phone use is often blamed for adolescent sleeping difficulties in the popular and scientific literature, with correlations observed between adolescents' mobile phone use and their bedtime. We aimed to obtain experimental evidence to support these causal claims. A within-subjects experiment (baseline, intervention) was conducted in adolescents' homes, to determine the effect of restricting adolescents' pre-bed mobile phone use on school night sleep habits. Following a baseline week, adolescents were given individualized phone stop times, 1 hour before bed for one school week. An online sleep diary was used to monitor bedtime, lights out time, sleep latency and total sleep. Sixty three adolescents (age range 14-18, M = 16.3, SD = 0.93yrs; 17%male) provided data. During one week of phone restriction, adolescents stopped using their phones earlier (80 min, p < .001), turned their lights off earlier (17 min, p = .01), and slept longer (21 min, p = .01). Participant recruitment was low (26%), indicating many adolescents lack motivation to negotiate changes to their evening phone use. Overall, there are potential benefits of restricted mobile phone use during the pre-sleep period, yet, future research is needed to identify non-technological interventions to increase adherence to phone restriction (e.g., motivational interviewing) or otherwise decrease pre-sleep arousal (e.g., cognitive strategies).

Double trouble: Weekend sleep changes are associated with increased impulsivity among adolescents with bipolar I disorder

OBJECTIVES

Both sleep disruption and impulsivity are important predictors of the course of bipolar disorder (BD). Although sleep disruption has been shown to intensify impulsivity, little research has considered how these two important domains interact within BD. Adolescence is a critical period for the onset of BD, and is often associated with increases in impulsivity and substantial changes in sleep. We tested the hypothesis that disruptions in sleep would increase impulsivity among adolescents, and that this effect would be more pronounced among those with BD.

METHODS

Thirteen- to nineteen-year-olds diagnosed with BD-I (n = 33, age [mean ± standard deviation (SD)] 16.2 ± 1.66 years, 54.5% female) and psychiatrically healthy controls (n = 26, age [mean ± SD] 15.5 ± 1.45 years, 55.6% female) reported their past-week bedtime, rise time, and sleep duration, separately for school days and weekends, and completed a self-report questionnaire on impulsivity. Stepwise regression was used to examine the effects of sleep on impulsivity, and the moderation of this effect by BD status.

RESULTS

Adolescents with BD reported significantly higher impulsivity, later and more variable rise time, and more variable time in bed and sleep duration on school days than did controls. Greater change in sleep duration between school days and weekends was associated with significantly more impulsivity among adolescents with BD as compared to controls.

CONCLUSIONS

These findings highlight the important effect of sleep on impulsivity among adolescents with BD and add to the growing evidence that establishing sleep routines may be an important therapeutic target for youth with BD.

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.

Changes in growth and sleep across school nights, weekends and a winter holiday period in two Australian schools

Studies suggest that there may be an association between sleep and growth; however, the relationship is not well understood. Changes in biology and external factors such as school schedule heavily impact the sleep of adolescents, during a critical phase for growth. This study assessed the changes in sleep across school days, weekends and school holidays, while also measuring height and weight changes, and self-reported alterations in food intake and physical activity. The impact of morningness-eveningness (M-E) on height change and weight gain was also investigated. In a sample of 63 adolescents (mean age = 13.13, SD = 0.33, 31 males) from two independent schools in South Australia, height and weight were measured weekly for 4 weeks prior to the school holidays and 4 weeks after the school holidays. Participants also completed a Morningness/Eveningness Scale and 7-day sleep, diet and physical activity diaries prior to, during and after the school holidays. Participants at one school had earlier wake times during the weekends than participants attending the other school, leading to a significantly shorter sleep duration on weekends for those participants. Regardless of school, sleep was significantly later and longer during the holidays (p < 0.001) and those with a stronger morning preference fell asleep (F_18,36 = 3.4, p = 0.001) and woke (F_18,44 = 2.0, p = 0.027) earlier than evening types. Growth rate was lower during the holiday weeks. For those attending the school with limited sleep in opportunities, growth after the holidays was lower for those with greater evening preference, whereas for those at the other school, growth was greater for those with greater evening preference. The increase in average weight from pre- to post-holidays was greater for those attending the school with limited opportunities to sleep longer. Participants reported greater food intake during the holidays compared to school days and greater physical activity levels on weekends compared to school days, and school days compared to holidays. Results suggest that time of day preference may impact growth, with evening types who cannot sleep in growing at a slower rate than evening types who can or morning types. This may be related to sleep restriction. Despite sleep being both later and longer during the school holidays, participants' growth slowed during the holiday period. It is possible that this may be a reflection of other behavioural changes in the holidays (increased food intake and reduced physical activity), as sleep timing during the school period was related to growth.

Human Adolescent Phase Response Curves to Bright White Light

Older adolescents are particularly vulnerable to circadian misalignment and sleep restriction, primarily due to early school start times. Light can shift the circadian system and could help attenuate circadian misalignment; however, a phase response curve (PRC) to determine the optimal time for receiving light and avoiding light is not available for adolescents. We constructed light PRCs for late pubertal to postpubertal adolescents aged 14 to 17 years. Participants completed 2 counterbalanced 5-day laboratory sessions after 8 or 9 days of scheduled sleep at home. Each session included phase assessments to measure the dim light melatonin onset (DLMO) before and after 3 days of free-running through an ultradian light-dark (wake-sleep) cycle (2 h dim [~20 lux] light, 2 h dark). In one session, intermittent bright white light (~5000 lux; four 20-min exposures) was alternated with 10 min of dim room light once per day for 3 consecutive days. The time of light varied among participants to cover the 24-h day. For each individual, the phase shift to bright light was corrected for the free-run derived from the other laboratory session with no bright light. One PRC showed phase shifts in response to light start time relative to the DLMO and another relative to home sleep. Phase delay shifts occurred around the hours corresponding to home bedtime. Phase advances occurred during the hours surrounding wake time and later in the afternoon. The transition from delays to advances occurred at the midpoint of home sleep. The adolescent PRCs presented here provide a valuable tool to time bright light in adolescents.

EEG Changes Accompanying Successive Cycles of Sleep Restriction With and Without Naps in Adolescents

Study objectives

To investigate the temporal evolution of sleep EEG changes in adolescents across two cycles of sleep restriction and recovery simulating an intense school week and to examine the effect of an afternoon nap on nocturnal sleep.

Methods

A parallel-group design, quasi-laboratory study was conducted in a student hostel. Fifty-seven adolescents (31 males, age = 15-19 years) were randomly assigned to nap or no nap groups. Participants underwent a 15-day protocol comprising two sleep restriction (5-hour time-in-bed [TIB]) and recovery (9-hour TIB) cycles. The nap group was also provided with a 1-hour nap opportunity at 14:00 following each sleep restriction night. Polysomnography recordings were obtained on nine nights and five nap episodes.

Results

Naps reduced homeostatic sleep pressure on sleep restriction nights as evidenced by longer N2 latency and reduced total sleep time (TST), sleep efficiency (SE), and slow wave energy. Sleep debt accumulated in both groups, evidenced by increased TST, greater SE, and reduced wake after sleep onset on recovery compared to baseline nights. Changes were greater in the no nap group. Recovery sleep after the first cycle of sleep restriction did not restore sleep architecture to baseline in either group. SE, rapid eye movement (REM), and non-REM sleep increased, and N2 latency was reduced in the second sleep restriction period.

Conclusions

Changes in sleep EEG induced by sleep restriction to 5-hour TIB for five nights were not eliminated after two nights of 9-hour recovery sleep. An afternoon nap helped but residual effects on the sleep EEG suggest that there is no substitute for adequate nocturnal sleep.