The adolescent decline of NREM delta, an indicator of brain maturation, is linked to age and sex but not to pubertal stage

Major Depressive Disorder Prediction Based on Sleep-Wake Disorders Symptoms in US Adolescents: A Machine Learning Approach from National Sleep Research Resource

Background

There is substantial evidence from previous studies that abnormalities in sleep parameters associated with depression are demonstrated in almost all stages of sleep architecture. Patients with symptoms of sleep-wake disorders have a much higher risk of developing major depressive disorders (MDD) compared to those without.

Objective

The aim of the present study is to establish and compare the performance of different machine learning models based on sleep-wake disorder symptoms data and to select the optimal model to interpret the importance of sleep-wake disorder symptoms to predict MDD occurrence in adolescents.

Methods

We derived data for this work from 2020 to 2021 Assessing Nocturnal Sleep/Wake Effects on Risk of Suicide Phase I Study from National Sleep Research Resource. Using demographic and sleep-wake disorder symptoms data as predictors and the occurrence of MDD measured base on the center for epidemiologic studies depression scale as an outcome, the following six machine learning predictive models were developed: eXtreme Gradient Boosting model (XGBoost), Light Gradient Boosting mode, AdaBoost, Gaussian Naïve Bayes, Complement Naïve Bayes, and multilayer perceptron. The models' performance was assessed using the AUC and other metrics, and the final model's predictor importance ranking was explained.

Results

XGBoost is the optimal predictive model in comprehensive performance with the AUC of 0.804 in the test set. All sleep-wake disorder symptoms were significantly positively correlated with the occurrence of adolescent MDD. The insomnia severity was the most important predictor compared with the other predictors in this study.

Conclusion

This machine learning predictive model based on sleep-wake disorder symptoms can help to raise the awareness of risk of symptoms between sleep-wake disorders and MDD in adolescents and improve primary care and prevention.

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.

To sleep or not to sleep - Effects on memory in normal aging and disease

Sleep behavior undergoes significant changes across the lifespan, and aging is associated with marked alterations in sleep amounts and quality. The primary sleep changes in healthy older adults include a shift in sleep timing, reduced slow-wave sleep, and impaired sleep maintenance. However, neurodegenerative and psychiatric disorders are more common among the elderly, which further worsen their sleep health. Irrespective of the cause, insufficient sleep adversely affects various bodily functions including energy metabolism, mood, and cognition. In this review, we will focus on the cognitive changes associated with inadequate sleep during normal aging and the underlying neural mechanisms.

Association between sleep and problematic behaviours in gifted children: a polysomnographic study

Neurological uniqueness, maladaptive behaviours, as well as atypical sleep patterns are reported to be defining characteristics of giftedness, but this has received little empirical support. We studied the polysomnography recorded sleep of gifted and typically-developing children together with features of maladaptive behaviours. The association of sleep macrostructure and sleep instability with maladaptive behaviours was also investigated in gifted children. In all, 19 gifted children (74% boys) and 17 typically-developing children (76% boys) aged 6-12 years were studied. Giftedness was identified using Renzulli's three-factor definition. The microarousal index, number of awakenings, and number of Stage shifts between sleep stages throughout the night were computed as sleep instability parameters. Maladaptive behaviours were assessed using the Child Behaviour Checklist. We found significantly more Stage N1 and less Stage N3 in gifted children compared to typically-developing children. More Stage N1 sleep was correlated with more externalising problems and less Stage N3 sleep was correlated with more internalising problems. Gifted children also displayed more rapid eye movement (REM) sleep, but this was not significantly correlated with behavioural scales. Gifted children displayed two opposing trends of sleep instability: more instability involving N1 sleep and less instability involving N2, N3 and REM sleep. More total Stage shifts were correlated with more internalising and externalising problems. The results of this study provide initial evidence of polysomnography-based characteristics of giftedness. Further studies are needed to explore common pathways linking sleep alterations and maladaptive behaviours in children with giftedness.

Sex differences in the sustained attention of elementary school children

BACKGROUND

The study investigates sex differences in sustained attention among children.

METHODS

Forty-five children (23 girls) from Grades 2-5 (mean age of 7.47 ± 0.73 years) wore an actigraph for a continuous five to seven days including school and non-school days. Sustained attention using the psychomotor vigilance test (PVT) was measured twice a day on two school days and on one non-school day.

RESULTS

No sex differences were found for sleep patterns. However, sex differences in PVT performance were documented. While boys were faster (shorter reaction time) and showed fewer lapses than girls, they showed higher number of false starts than girls, on both weekdays and weekends.

CONCLUSIONS

The findings suggest that sex differences should been taken into account in studies investigating neurobehavioral functioning, particularly, sustained attention across various age groups.

Elevated beta activity in the nighttime sleep and multiple sleep latency electroencephalograms of chronic insomnia patients

Aim

To examine the 24-h hyperarousal hypothesis of insomnia using electroencephalographic (EEG) spectral analysis of overnight polysomnography (PSG) and daytime multiple sleep latency tests (MSLTs).

Methods

Standard PSG and MSLT were recorded in 31 chronic insomniacs (CIs) (21 females, mean age 36.19) and in 21 normal controls (NCs) (18 females, mean age 34.76). EEG spectral analyses were conducted and relative power was obtained for each sleep stage during PSG and each session during MSLTs. Subsequently, CIs were subdivided based on sleep efficiency (SE < or ≥ 85%) or mean sleep latency (MSL) of MSLT (< or ≥ 15 min), and beta power was compared among NCs and CIs subgroups. General liner regression analyses of beta power and PSG parameters were conducted.

Results

CIs had significantly greater beta power in nighttime W, N1, N2, NREM, and in total overnight and in MSLT sessions compared with NCs. CIs with lower PSG-SE or longer MSLT-MSL showed higher beta power at nighttime. Compared with NCs, increased beta power was limited to CIs with lower PSG-SE or longer MSLT-MSL during MSLT sessions. In all subjects, total daytime beta was positively correlated to total overnight beta and MSL, total overnight beta was negatively related to SE. In CIs, total daytime beta and total overnight beta were positively correlated.

Conclusion

Our results support the hypothesis of 24-h cortical hyperarousal in insomnia. We conclude that 24-h cortical hyperarousal is clearly present in insomnia and is greater in insomnia with objective findings.

Sleep homeostasis, seizures, and cognition in children with focal epilepsy

AIM

To investigate the link between sleep disruption and cognitive impairment in childhood epilepsy by studying the effect of epilepsy on sleep homeostasis, as reflected in slow-wave activity (SWA).

METHOD

We examined SWA from overnight EEG-polysomnography in 19 children with focal epilepsy (mean [SD] age 11 years 6 months [3 years], range 6 years 6 months-15 years 6 months; 6 females, 13 males) and 18 age- and sex-matched typically developing controls, correlating this with contemporaneous memory consolidation task scores, full-scale IQ, seizures, and focal interictal discharges.

RESULTS

Children with epilepsy did not differ significantly from controls in overnight SWA decline (p = 0.12) or gain in memory performance with sleep (p = 0.27). SWA was lower in patients compared to controls in the first hour of non-rapid eye movement sleep (p = 0.021), although not in those who remained seizure-free (p = 0.26). Full-scale IQ did not correlate with measures of SWA in patients or controls. There was no significant difference in SWA measures between focal and non-focal electrodes.

INTERPRETATION

Overnight SWA decline is conserved in children with focal epilepsy and may underpin the preservation of sleep-related memory consolidation in this patient group. Reduced early-night SWA may reflect impaired or immature sleep homeostasis in those with a higher seizure burden.

Sleep Instability Correlates with Attentional Impairment in Boys with Attention Deficit Hyperactivity Disorder

Theoretical models of sleep and attention deficit hyperactivity disorder (ADHD) suggest that symptoms of ADHD are associated with daytime sleepiness, but it has received little support. The present study aimed at testing an alternative model involving the association of attentional instability with sleep instability, i.e., sleep stage transitions and arousals. Twelve ADHD and 15 healthy control (HC) boys aged between 8 and 12 years old underwent polysomnography recording and attentional testing. The microarousal index, the number of awakenings, and the number of stage shifts between stages 1, 2, 3, 4 and REM sleep throughout the night were computed as sleep stability parameters. Attentional functioning was assessed using the Continuous Performance Test-II. We found significantly higher sleep instability in ADHD compared to HC. Sleep arousals and stage transitions (micro arousal index, stage 4/3 and 2/4 transitions) in ADHD significantly correlated with lower attentional scores. No association whatsoever was found between sleep instability and attentional functioning in HC. The results show that sleep instability is associated with lower attentional performance in boys with ADHD, but not in HC. This could be compatible with a model according to which attention and sleep stability share a common neural substrate in ADHD.

Using Heartfulness Meditation and Brainwave Entrainment to Improve Teenage Mental Wellbeing

Teenagers are highly susceptible to mental health issues and this problem has been exacerbated by the quarantine restrictions of COVID-19. This study evaluated the use of Heartfulness Meditation and Audio Brainwave Entrainment to help teenagers cope with mental health issues. It used 30-min Heartfulness meditation and 15-min brainwave entrainment sessions with binaural beats and isochronic tones three times a week for 4 weeks. Using a pretest-posttest methodology, participants were asked to complete a survey battery including the Pittsburgh Quality of Sleep Index, Perceived Stress Scale, Patient Health Question-9, Profile of Mood States, and Cambridge Brain Health assessment. Participants (n = 40) were divided into four experimental groups: the control group (n = 9), Audio Brainwave Entrainment group (n = 9), Heartfulness Meditation group (n = 10), and a combined group (n = 12), for a 4-week intervention. Data were analyzed with paired t-tests. The singular Audio Brainwave Entrainment group did not see statistically significant improvements, nor did any of the intervention groups for brain health (p > 0.05). This study, however, proved the efficacy of a 4-week Heartfulness Meditation program to regulate overall mood (p = 0.00132), stress levels (p = 0.0089), state depression (POMS; p = 0.0037), and anger (p = 0.002). Results also suggest adding Audio Brainwave Entrainment to Heartfulness Meditation may improve sleep quality (p = 0.0377) and stress levels (p = 0.00016).

Trajectories of brain development reveal times of risk and factors promoting resilience to alcohol use during adolescence

Alcohol use disorder (AUD) is recognized as harmful for the developing brain. Numerous studies have sought environmental and genetic risk factors that predict the development of AUD, but recently identified resilience factors have emerged as protective. This chapter reviews normal processes of brain development in adolescence and emerging adulthood, delineates disturbed growth neurotrajectories related to heavy drinking, and identifies potential endogenous, experiential, and time-linked brain markers of resilience. For example, concurrent high dorsolateral prefrontal activation serving inhibitory control and low nucleus accumbens activation serving reward functions engender positive adaptation and low alcohol use. Also discussed is the role that moderating factors have in promoting risk for or resilience to AUD. Longitudinal research on the effects of all levels of alcohol drinking on the developing brain remains crucial and should be pursued in the context of resilience, which is a promising direction for identifying protective biomarkers against developing AUDs.

Cortical Thinning and Sleep Slow Wave Activity Reductions Mediate Age-Related Improvements in Cognition During Mid-Late Adolescence

Study Objectives

Gains in cognitive test performance that occur during adolescence are associated with brain maturation. Cortical thinning and reduced sleep slow wave activity (SWA) are markers of such developmental changes. Here we investigate whether they mediate age-related improvements in cognition.

Methods

109 adolescents aged 15–19 years (49 males) underwent magnetic resonance imaging, polysomnography (PSG), and a battery of cognitive tasks within a 2-month time window. Cognitive tasks assessed nonverbal intelligence, sustained attention, speed of processing and working memory and executive function. To minimize the effect of sleep history on SWA and cognitive performance, PSG and test batteries were administered only after at least 8 nights of 9-h time-in-bed (TIB) sleep opportunity.

Results

Age-related improvements in speed of processing (r = 0.33, p = 0.001) and nonverbal intelligence (r = 0.24, p = 0.01) domains were observed. These cognitive changes were associated with reduced cortical thickness, particularly in bilateral temporoparietal regions (rs = −0.21 to −0.45, ps < 0.05), as well as SWA (r = −0.35, p < 0.001). Serial mediation models found that ROIs in the middle/superior temporal cortices, together with SWA mediated the age-related improvement observed on cognition.

Conclusions

During adolescence, age-related improvements in cognition are mediated by reductions in cortical thickness and sleep SWA.

A nationwide cross-sectional study of difficulty waking up for school among adolescents

STUDY OBJECTIVES

To determine the prevalence of and risk-factors for difficulty waking up for school among adolescents.

METHODS

We used a self-administered questionnaire (140 junior high schools [JHSs]; 124 senior high schools [SHSs]) selected randomly in 2012 from throughout Japan.

RESULTS

Total response rate: 60.7%. Data from 38,494 JHS and 61,556 SHS students were analyzed. The prevalence of at least one instance of school tardiness/absence due to difficulty waking up over a 30-day period was 10.9(95% confidence-interval:10.5-11.3)%/2.9(2.7-3.1)% for JHS-boys and 7.7(7.3-8.1)%/2.0(1.8-2.2)% for JHS-girls. The prevalence was 15.5(15.1-15.9)%/5.6(5.3-5.9)% for SHS-boys and 14.4(14.0-14.8)%/5.9(5.6-6.2)% for SHS-girls. We used ordinal regression to identify the risk factors associated with the experience of school tardiness/absence. Factors significantly associated with school tardiness in all four groups (JHS boys/girls, SHS boys/girls) were "no-participation-in-club-activities," "early-morning-awakening," "feeling bad throughout a morning," "drinking," and "smoking." Among associated factors, the highest odds ratio was found for monthly smoking-days (none vs. at least one-day or more) for JHS-girls at 5.30(3.57-7.85). Factors significantly associated with school absence in all four groups were "no wishing to go to university," "no participation in club activities," "disorders of initiating and maintaining sleep," "long internet use," "drinking," "smoking," "poor-mental-health" and "feeling bad throughout a morning." Among associated factors, the highest odds ratio was found for monthly smoking-days (none vs. at least one-day or more) for JHS-girls at 4.60(3.45-6.15).

CONCLUSIONS

These results suggest that the risk factors for difficulty waking up among adolescents are sleep status, lifestyle, and mental health, which can indicate the presence of an underlying disease.

Maturational trajectories of non-rapid eye movement slow wave activity and odds ratio product in a population-based sample of youth

BACKGROUND

Brain maturation is reflected in the sleep electroencephalogram (EEG) by a decline in non-rapid eye movement (NREM) slow wave activity (SWA) throughout adolescence and a related decrease in sleep depth. However, this trajectory and its sex and pubertal differences lack replication in population-based samples. We tested age-related changes in SWA (0.4-4 Hz) power and odds ratio product (ORP), a standardized measure of sleep depth.

METHODS

We analyzed the sleep EEG of 572 subjects aged 6-21 y (48% female, 26% racial/ethnic minority) and 332 subjects 5-12 y followed-up at 12-22 y. Multivariable-adjusted analyses tested age-related cross-sectional and longitudinal trajectories of SWA and ORP.

RESULTS

SWA remained stable from age 6 to 10, decreased between ages 11 and 17, and plateaued from age 18 to 21 (p-cubic<0.001); females showed a longitudinal decline 23% greater than males by 13 y, while males experienced a steeper slope after 14 y and their longitudinal decline was 21% greater by 19 y. More mature adolescents (75% female) experienced a greater longitudinal decline in SWA than less mature adolescents by 14 y. ORP showed an age-related increasing trajectory (p-linear<0.001) with no sex or pubertal differences.

CONCLUSIONS

We provide population-level evidence for the maturational decline and sex and pubertal differences in SWA in the transition from childhood to adolescence, while introducing ORP as a novel metric in youth. Along with previous studies, the distinct trajectories observed suggest that age-related changes in SWA reflect brain maturation and local/synaptic processes during this developmental period, while those of ORP may reflect global/state control of NREM sleep depth.

Gender differences in adolescent sleep neurophysiology: a high-density sleep EEG study

During adolescence, differences between males and females in physiology, behavior and risk for psychopathology are accentuated. The goal of the current study was to examine gender differences in sleep neurophysiology using high-density sleep EEG in early adolescence. We examined gender differences in sleep EEG power and coherence across frequency bands for both NREM and REM sleep in a sample of 61 adolescents (31 girls and 30 boys; mean age = 12.48; SD = 1.34). In addition, sleep spindles were individually detected and characterized. Compared to boys, girls had significantly greater spindle activity, as reflected in higher NREM sigma power, spindle amplitude, spindle frequency and spindle density over widespread regions. Furthermore, power in higher frequency bands (16.2–44 Hz) was larger in girls than boys in a state independent manner. Oscillatory activity across frequency bands and sleep states was generally more coherent in females as compared to males, suggesting greater connectivity in females. An exception to this finding was the alpha band during NREM and REM sleep, where coherence was higher (NREM) or not different (REM) in boys compared to girls. Sleep spindles are generated through thalamocortical circuits, and thus, the greater spindle activity across regions in females may represent a stronger thalamocortical circuit in adolescent females as compared to males. Moreover, greater global connectivity in females may reflect functional brain differences with implications for cognition and mental health. Given the pronounced gender differences, our study highlights the importance of taking gender into account when designing and interpreting studies of sleep neurophysiology.

Splice-dependent trans-synaptic PTPδ-IL1RAPL1 interaction regulates synapse formation and non-REM sleep

Alternative splicing regulates trans‐synaptic adhesions and synapse development, but supporting in vivo evidence is limited. PTPδ, a receptor tyrosine phosphatase adhering to multiple synaptic adhesion molecules, is associated with various neuropsychiatric disorders; however, its in vivo functions remain unclear. Here, we show that PTPδ is mainly present at excitatory presynaptic sites by endogenous PTPδ tagging. Global PTPδ deletion in mice leads to input‐specific decreases in excitatory synapse development and strength. This involves tyrosine dephosphorylation and synaptic loss of IL1RAPL1, a postsynaptic partner of PTPδ requiring the PTPδ‐meA splice insert for binding. Importantly, PTPδ‐mutant mice lacking the PTPδ‐meA insert, and thus lacking the PTPδ interaction with IL1RAPL1 but not other postsynaptic partners, recapitulate biochemical and synaptic phenotypes of global PTPδ‐mutant mice. Behaviorally, both global and meA‐specific PTPδ‐mutant mice display abnormal sleep behavior and non‐REM rhythms. Therefore, alternative splicing in PTPδ regulates excitatory synapse development and sleep by modulating a specific trans‐synaptic adhesion.

Adolescent-Sleep-Intervention Research: Current State and Future Directions

Emerging evidence suggests that cognitive-behavioral interventions should be considered as a first-line treatment for adolescent sleep problems and can also address associated mental health concerns. This article’s aim is to prioritize future directions for this research. Studies are needed that (a) leverage innovative technology, which may allow for a more personalized-medicine approach to care; (b) use alternative research designs, such as treatment-optimization strategies; (c) evaluate mechanisms of therapeutic improvements, including mediators and moderators of change, predictors of treatment adherence, dose–response relationships, and specificity of effects of different treatment components; (d) “scale up” the interventions so that a large proportion of adolescents can access them; and (e) develop flexible approaches to delivery (e.g., online platforms) and stepped-care guidelines. National and international standards of secondary school start times of 8:30 a.m. or later are also needed. The field is now mature enough to take these next steps, which will enhance the effectiveness and public health impact of these interventions.

Sleep spindle characteristics in adolescents

OBJECTIVE

Sleep changes substantially during adolescence; however, our understanding of age-related differences in specific electroencephalographic waveforms during this developmental period is limited.

METHOD

Sigma power, spindle characteristics and cognitive data were calculated for fast (∼13 Hz) central and slow (∼11 Hz) frontal sleep spindles for a large cross-sectional sample of adolescents (N = 134, aged 12-21 years, from the National Consortium on Alcohol and NeuroDevelopment in Adolescence (NCANDA) study).

RESULTS

Older age (and advanced pubertal development) was associated with lower absolute sigma power and greater fast spindle density, with spindles having a shorter duration and smaller amplitude and occurring at a faster average frequency than at a younger age. Spindle characteristics were not directly associated with cognition. An indirect relationship (age * density) provided some evidence for an association between better episodic memory performance and greater spindle density only for younger adolescents.

CONCLUSION

Spindle characteristics in adolescents differed according to age, possibly reflecting underlying differences in thalamo-cortical connectivity, and may play a role in episodic memory early in adolescence.

SIGNIFICANCE

Sleep spindles may serve as a marker of adolescent development, likely reflecting brain maturational status. Investigating specific spindle characteristics, in addition to sigma power, is necessary to fully characterize spindles during adolescence.

Local Differences in Computational Sleep Depth Parameters in Healthy School-aged Children

OBJECTIVE

Slow wave sleep in children reflects several processes, such as sleep pressure, synaptic density, and cortical maturation. Deep sleep in children is abundant and our aim was to discover whether examining electroencephalography (EEG) mean frequency would help separate these processes.

METHODS

Sleep EEG of 28 generally healthy 7- to 11-year-old children (14 first graders, 14 third graders, 14 girls, 14 boys) was analyzed. Median non-rapid eye movement (NREM) sleep EEG frequency (median sleep depth, in Hz) and the amount of computational deep sleep using the thresholds of 2 Hz and 4 Hz (DS2% and DS4%, respectively) were calculated from the frontopolar, central, and occipital EEG derivations.

RESULTS

Median NREM sleep frequency was lower in the left frontopolar area than more posteriorly in the whole study group, in the third graders and in the girls. In the left hemisphere, the amount of DS4% was higher frontopolarly than occipitally in the third graders and in the girls. The amount of DS2% was higher frontopolarly than centrally in all groups except in the first graders. In the whole study group, DS4% declined smoothly across the NREM episodes, whereas DS2% centered in the first NREM sleep episode.

DISCUSSION

The median NREM sleep EEG frequency results might denote earlier frontal maturation in girls than in boys. Interestingly, we found frontopolar predominance in slow mean EEG frequency in both hemispheres, even if frontal slow wave activity is found to enhance until adolescence. As with infants, it seems that slower sleep EEG frequencies do not reflect sleep pressure as well as <4 Hz activity in school-aged children either.

CONCLUSION

Our analysis method suggests that in addition to slow wave activity, EEG frequency analysis might be useful in differentiating between the different sleep related processes in children.

The mediating role of cortical thickness and gray matter volume on sleep slow-wave activity during adolescence

During the course of adolescence, reductions occur in cortical thickness and gray matter (GM) volume, along with a 65% reduction in slow-wave (delta) activity during sleep (SWA) but empirical data linking these structural brain and functional sleep differences, is lacking. Here, we investigated specifically whether age-related differences in cortical thickness and GM volume and cortical thickness accounted for the typical age-related difference in slow-wave (delta) activity (SWA) during sleep. 132 healthy participants (age 12-21 years) from the National Consortium on Alcohol and NeuroDevelopment in Adolescence study were included in this cross-sectional analysis of baseline polysomnographic, electroencephalographic, and magnetic resonance imaging data. By applying mediation models, we identified a large, direct effect of age on SWA in adolescents, which explained 45% of the variance in ultra-SWA (0.3-1 Hz) and 52% of the variance in delta-SWA (1 to <4 Hz), where SWA was lower in older adolescents, as has been reported previously. In addition, we provide evidence that the structure of several, predominantly frontal, and parietal brain regions, partially mediated this direct age effect, models including measures of brain structure explained an additional 3-9% of the variance in ultra-SWA and 4-5% of the variance in delta-SWA, with no differences between sexes. Replacing age with pubertal status in models produced similar results. As reductions in GM volume and cortical thickness likely indicate synaptic pruning and myelination, these results suggest that diminished SWA in older, more mature adolescents may largely be driven by such processes within a number of frontal and parietal brain regions.

Sleep and slow-wave activity in depressed adolescent boys: a preliminary study

OBJECTIVE

Adolescence is a vulnerable period of life that is characterized by increasing incidence of depression. Sleep disturbance is one of the diagnostic symptoms of depressive disorder. Adolescence is also characterized by dramatic maturational changes in sleep and its regulation. The goal of this study was to assess sleep macroarchitecture and slow-wave activity (SWA) in depressed adolescent boys.

METHODS

Eight non-medicated adolescent boys meeting the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV) criteria for depressive disorder and 10 age-matched healthy controls (average age 16.0 years) underwent polysomnography in their home environment for two consecutive nights. Sleep macroarchitecture, SWA, and SWA dissipation were assessed in all subjects.

RESULTS

Depressed boys showed a flattened pattern of SWA dissipation through the night. SWA power was lower during the first non-rapid eye movement (NREM) episode in the frontal derivation and higher during the third NREM episode in the central derivation in the group of depressed boys as compared to healthy boys. The SWA dissipation pattern correlated with the severity of depressive symptoms, and the correlation was strongest in the frontal derivation. In addition, total sleep time was shorter in patients as compared to the control group, but no other differences were found in the macroarchitecture of sleep.

CONCLUSION

Depression in adolescent boys is characterized by more evenly distributed SWA through the night as compared to healthy subjects, and we showed for the first time that this pattern of SWA distribution is associated with severity of depressive symptoms. These findings suggest that homeostatic regulation of sleep may be impaired in adolescent depression.

More Effective Consolidation of Episodic Long-Term Memory in Children Than Adults-Unrelated to Sleep

Abilities to encode and remember events in their spatiotemporal context (episodic memory) rely on brain regions that mature late during childhood and are supported by sleep. We compared the temporal dynamics of episodic memory formation and the role of sleep in this process between 62 children (8-12 years) and 57 adults (18-37 years). Subjects recalled "what-where-when" memories after a short 1-hr retention interval or after a long 10.5-hr interval containing either nocturnal sleep or daytime wakefulness. Although children showed diminished recall of episodes after 1 hr, possibly resulting from inferior encoding, unlike adults, they showed no further decrease in recall after 10.5 hr. In both age groups, episodic memory benefitted from sleep. However, children's more effective offline retention was unrelated to sleep.

Sleep Duration and Sleep Quality: Associations With Depressive Symptoms Across Adolescence

This study explored whether short sleep duration and sleep quality mediate the relationship between age and depressive symptoms. For comparison, we also explored whether depressive symptoms mediate the relationship between age and short sleep duration and sleep quality. The sample comprised 741 adolescents (63.5% female, mean age 15.78 years, range 11.92-19.67 years) in grades 7-12 from 11 secondary schools in metropolitan Melbourne, Australia. Students completed the Pittsburgh Sleep Quality Index (PSQI) and Center for Epidemiologic Studies Depression Scale (CES-D). Path analyses suggested that short sleep duration significantly mediated the relationship between age and depressive symptoms. Poor sleep quality also significantly mediated this relationship when sleep quality was defined by subjective judgement, but not sleep disturbance, sleep efficiency, or sleep onset latency. Depressive symptoms significantly mediated the relationship between age and short sleep duration and sleep quality (subjective judgement, sleep disturbance, sleep efficiency, and sleep onset latency). These findings suggest that the population-wide increase in depressive symptoms across adolescence is partially mediated by sleep-related developmental changes. They also highlight the importance of examining specific sleep problems when investigating the relationship between sleep and mood in this age group.

Sleep disturbances in adolescents with ADHD: A systematic review and framework for future research

BACKGROUND

Biological mechanisms underlying symptom and prognostic heterogeneity in Attention-Deficit/Hyperactivity Disorder (ADHD) are unclear. Sleep impacts neurocognition and daytime functioning and is disrupted in ADHD, yet little is known about sleep in ADHD during adolescence, a period characterized by alterations in sleep, brain structure, and environmental demands as well as diverging ADHD trajectories.

METHODS

A systematic review identified studies published prior to August 2016 assessing sleep in adolescents (aged 10-19years) with ADHD or participating in population-based studies measuring ADHD symptoms.

RESULTS

Twenty-five studies were identified (19 subjective report, 6 using actigraphy/polysomnography). Findings are mixed but overall suggest associations between sleep disturbances and 1) ADHD symptoms in the population and 2) poorer clinical, neurocognitive, and functional outcomes among adolescents with ADHD. Common limitations of studies included small or non-representative samples, non-standardized sleep measures, and cross-sectional methodology.

CONCLUSIONS

Current data on sleep in adolescent ADHD are sparse and limited by methodological concerns. Future studies are critical for clarifying a potential role of sleep in contributing to heterogeneity of ADHD presentation and prognosis. Potential mechanisms by which sleep disturbances during adolescence may contribute to worsened symptom severity and persistence of ADHD into adulthood and an agenda to guide future research are discussed.

Caffeine Consuming Children and Adolescents Show Altered Sleep Behavior and Deep Sleep

Caffeine is the most commonly ingested psychoactive drug worldwide with increasing consumption rates among young individuals. While caffeine leads to decreased sleep quality in adults, studies investigating how caffeine consumption affects children's and adolescents' sleep remain scarce. We explored the effects of regular caffeine consumption on sleep behavior and the sleep electroencephalogram (EEG) in children and adolescents (10-16 years). While later habitual bedtimes (Caffeine 23:14 ± 11.4, Controls 22:17 ± 15.4) and less time in bed were found in caffeine consumers compared to the control group (Caffeine 08:10 ± 13.3, Controls 09:03 ± 16.1), morning tiredness was unaffected. Furthermore, caffeine consumers exhibited reduced sleep EEG slow-wave activity (SWA, 1-4.5 Hz) at the beginning of the night compared to controls (20% ± 9% average reduction across all electrodes and subjects). Comparable reductions were found for alpha activity (8.25-9.75 Hz). These effects, however, disappeared in the morning hours. Our findings suggest that caffeine consumption in adolescents may lead to later bedtimes and reduced SWA, a well-established marker of sleep depth. Because deep sleep is involved in recovery processes during sleep, further research is needed to understand whether a caffeine-induced loss of sleep depth interacts with neuronal network refinement processes that occur during the sensitive period of adolescent development.

Sleep/Wake Dynamics Changes during Maturation in Rats

Objectives

Conventional scoring of sleep provides little information about the process of transitioning between vigilance states. We applied the state space technique (SST) using frequency band ratios to follow normal maturation of different sleep/wake states, velocities of movements, and transitions between states of juvenile (postnatal day 34, P34) and young adult rats (P71).

Design

24-h sleep recordings of eight P34 and nine P71 were analyzed using conventional scoring criteria and SST one week following implantation of telemetric transmitter. SST is a non-categorical approach that allows novel quantitative and unbiased examination of vigilance-states dynamics and state transitions. In this approach, behavioral changes are described in a 2-dimensional state space that is derived from spectral characteristics of the electroencephalography.

Measurements and Results

With maturation sleep intensity declines, the duration of deep slow wave sleep (DSWS) and light slow wave sleep (LSWS) decreases and increases, respectively. Vigilance state determination, as a function of frequency, is not constant; there is a substantial shift to higher ratio 1 in all vigilance states except DSWS. Deep slow wave sleep decreases in adult relative to juvenile animals at all frequencies. P71 animals have 400% more trajectories from Wake to LSWS (p = 0.005) and vice versa (p = 0.005), and 100% more micro-arousals (p = 0.021), while trajectories from LSWS to DSWS (p = 0.047) and vice versa (p = 0.033) were reduced by 60%. In both juvenile and adult animals, no significant changes were found in sleep velocity at all regions of the 2-dimensional state space plot; suggesting that maturation has a partial effect on sleep stability.

Conclusions

Here, we present novel and original evidence that SST enables visualization of vigilance-state intensity, transitions, and velocities that were not evident by traditional scoring methods. These observations provide new perspectives in sleep state dynamics and highlight the usefulness of this technique in exploring the development of sleep-wake activity.

Sleep in adolescent depression: physiological perspectives

Depression and disturbed sleep are intimately and bidirectionally related. During adolescence, the incidence of both insomnia and major depression increases simultaneously, in a gender-specific manner. The majority of depressed adolescents suffer from different types of subjective sleep complaints. Despite these complaints, the results from polysomnographic studies in depressed adolescents remain inconsistent. In general, similar features to those seen among adults with depressive disorder (e.g. abnormalities in rapid eye movement sleep and difficulties in sleep onset) have been reported, but expressed to a lesser degree. The inconsistency in findings may be linked with maturational factors, factors related to the stage of illness and greater heterogeneity in the clinical spectrum of depression among adolescents. The exact neurobiological mechanisms by which sleep alterations and depression are linked during adolescence are not fully understood. Aberrations in brain maturation, expressed at different levels of organization, for example gene expression, neurotransmitter and hormone metabolism, and activity of neuronal networks have been suggested. The circadian systems may change in adolescent depression beyond that observed during healthy adolescent development (i.e. beyond the typical circadian shift towards eveningness). A number of therapeutic approaches to alleviate sleep disruption associated with depression have been proposed, but research on the efficacy of these interventions in adolescents is lacking. Knowledge of the neurobiological links between sleep and depression during adolescence could lead to new insights into effective prevention and treatment of depression.

Advancing a biopsychosocial and contextual model of sleep in adolescence: a review and introduction to the special issue

Sleep problems in adolescence have been identified as an international public health issue. Over the past few decades, notable advances have been made in our understanding of the patterns and consequences of sleep in adolescence. Despite these important gains, there is much about the role of sleep in adolescence that remains to be understood. This Special Issue brings together studies that examine sleep as it specifically pertains to adolescent development and adjustment. In this introductory article, we argue for the importance of grounding the study of sleep and adolescence in developmental science and a developmental psychopathology framework. First, a review of the literature is used to outline a biopsychosocial and contextual model of sleep in adolescence. Second, attention-deficit/hyperactivity disorder (ADHD) is used as an exemplar of the proposed model given the pervasiveness of sleep problems among youth with ADHD and the likelihood that sleep problems and ADHD symptoms are interconnected in complex ways. Finally, a brief introduction to the empirical articles included in the Special Issue is provided, with particular attention given to how these articles fit within the proposed biopsychosocial and contextual model. Along with the framework proposed in this article, the studies included in this Special Issue advance the current literature and point to critical directions for future research.

Developmental changes in sleep and their relationships to psychiatric illnesses

PURPOSE OF REVIEW

Sleep undergoes major changes during development. Its relationship to the complex process of maturation in health and disease has recently received increased attention. This review aims to highlight the recent literature examining the interplay of altered sleep, brain development and emerging psychiatric illnesses in children and adolescents.

RECENT FINDINGS

In addition to a temporal relationship of sleep disturbances preceding the onset of psychiatric illnesses, a bi-directional interaction of altered sleep and symptom severity has increasingly been shown. Sleep architecture shows drastic age-dependent alterations on a structural level during the first 2 decades of life. However, findings regarding disease-specific patterns have remained inconsistent. On a functional level, recent evidence about sleep electroencephalographic characteristics points to a close relationship between slow waves, reflecting the depth of sleep, and cortical plasticity.

SUMMARY

Sleep provides a rich source of information to gain insight into both the healthy and disturbed processes of brain function and maturation. Emerging data suggest that the investigation of slow wave activity is a novel and promising tool for monitoring both of these processes. It is important to understand when and how deviations from typical developmental sleep alterations occur in order to improve prevention and early treatment of disorders affecting a substantial number of children and adolescents.

The sleep EEG topography in children and adolescents shows sex differences in language areas

The topographic distribution of slow wave activity (SWA, EEG power between 0.75 and 4.5 Hz) during non-rapid eye movement (NREM) sleep was proposed to mirror cortical maturation with a typical age-related pattern. Here, we examined whether sex differences occur in SWA topography of children and adolescents (22 age-matched subjects, 11 boys, mean age 13.4 years, range: 8.7-19.4, and 11 girls, mean age 13.4 years, range: 9.1-19.0 years). In females, SWA during the first 60 min of NREM sleep was higher over bilateral cortical areas that are related to language functions, while in males SWA was increased over the right prefrontal cortex, a region also involved in spatial abilities. We conclude that cortical areas governing functions in which one sex outperforms the other exhibit increased sleep SWA and, thus, may indicate maturation of sex-specific brain function and higher cortical plasticity during development.

Altered sleep in Borderline Personality Disorder in relation to the core dimensions of psychopathology

The aim of the study was to review the literature regarding sleep disturbances in Borderline Personality Disorder (BPD) and to relate the reported sleep alterations to the underlying core dimensions of BPD pathology. We present a qualitative and theoretical review regarding the empirical studies that investigated objective and subjective sleep quality in BPD and in different psychiatric conditions showing high co-morbidity with this disorder. We show that disturbed sleep including sleep fragmentation, alterations in Slow Wave Sleep and REM sleep, and dysphoric dreaming are prevalent symptoms in BPD. We provide a framework relating the specific sleep alterations to the core dimensions of BPD pathology in order to clarify the inconsistencies of the different findings. The specific sleep disturbances in BPD seem to be related to different dimensions of psychopathological functioning and may have detrimental consequences on waking affect and cognition. Investigating disturbed sleep in BPD in relation to waking symptoms and underlying neural functioning would shed more light on the nature of this complex disorder. Moreover, a stronger emphasis on sleep disturbances would enrich the treatment protocols of BPD.

Sex, puberty, and the timing of sleep EEG measured adolescent brain maturation

The steep adolescent decline in the slow wave (delta, 1-4 Hz) electroencephalogram (EEG) of nonrapid eye movement (NREM) sleep is a dramatic maturational change in brain electrophysiology thought to be driven by cortical synaptic pruning. A perennial question is whether this change in brain electrophysiology is related to sexual maturation. Applying Gompertz growth models to longitudinal data spanning ages 9-18 y, we found that the timing of the delta decline was significantly (P < 0.0001) linked to timing of pubertal maturation. This timing relation remained significant when sex differences in the timing of the delta decline were statistically controlled. Sex differences and the relation to the timing of puberty jointly explained 67% of the between-subject variance in the timing of the delta decline. These data provide a demonstration of a temporal relation between puberty and an electrophysiological marker of adolescent brain development. They can guide research into whether the neuroendocrine events of puberty are mechanistically linked to cortical maturation or whether, instead, the two maturational processes are parallel but independent programs of human ontogenesis.

Developmental changes in the sleep electroencephalogram of adolescent boys and girls

The sleep electroencephalogram (EEG) changes across adolescence; however, there are conflicting data as to whether EEG changes are regionally specific, are evident in non-rapid eye movement (NREM) and rapid eye movement (REM) sleep, and whether there are sex differences. The present study seeks to resolve some of these issues in a combined cross-sectional and longitudinal analysis of sleep EEG in adolescents. Thirty-three healthy adolescents (18 boys, 15 girls; 11-14 years) were studied on two occasions 6-8 months apart. Cross-sectional analysis of data from the initial visit revealed significantly less slow-wave sleep, delta (0.3 to <4 Hz) and theta (4 to <8 Hz) power in both NREM and REM sleep with advancing age. The age-delta power relationship was significant at the occipital site, with age accounting for 26% of the variance. Longitudinal analysis revealed that NREM delta power declined significantly from the initial to follow-up visit, in association with declining delta amplitude and incidence (P < 0.01), with the effect being greatest at the occipital site. REM delta power also declined over time in association with reduced amplitude (P < 0.01). There were longitudinal reductions in theta, alpha and sigma power in NREM and REM sleep evident at the occipital site at follow-up (P < 0.01). No sex differences were apparent in the pattern of change with age for NREM or REM sleep. Declines in sleep EEG spectral power occur across adolescence in both boys and girls, particularly in the occipital derivation, and are not state-specific, occurring in both NREM and REM sleep.

Sleep EEG provides evidence that cortical changes persist into late adolescence

STUDY OBJECTIVES

To examine developmental changes in the human sleep electroencephalogram (EEG) during late adolescence.

SETTING

A 4-bed sleep laboratory.

PARTICIPANTS

Fourteen adolescents (5 boys) were studied at ages 15 or 16 (initial) and again at ages 17 to 19 (follow-up).

INTERVENTIONS

N/A.

MEASUREMENTS AND RESULTS

All-night polysomnography was recorded at each assessment and scored according to the criteria of Rechtschaffen and Kales. A 27% decline in duration of slow wave sleep, and a 22% increase of stage 2 sleep was observed from the initial to the follow-up session. All-night spectral analysis of 2 central and 2 occipital leads revealed a significant decline of NREM and REM sleep EEG power with increasing age across frequencies in both states. Time-frequency analysis revealed that the decline in power was consistent across the night for all bands except the delta band. The decreases in power were most pronounced over the left central (C3/A2) and right occipital (O2/A1) derivations.

CONCLUSIONS

Using longitudinal data, we show that the developmental changes to the sleeping EEG that begin in early adolescence continue into late adolescence. As with early adolescents, we observed hemispheric asymmetry in the decline of sleep EEG power. This decline was state and frequency nonspecific, suggesting that it may be due to the pruning of synapses known to occur during adolescence.

Developmental change in regional brain structure over 7 months in early adolescence: comparison of approaches for longitudinal atlas-based parcellation

Early adolescence is a time of rapid change in neuroanatomy and sexual development. Precision in tracking changes in brain morphology with structural MRI requires image segmentation with minimal error. Here, we compared two approaches to achieve segmentation by image registration with an atlas to quantify regional brain structural development over a 7-month interval in normal, early adolescent boys and girls. Adolescents were scanned twice (average interval=7.3 months), yielding adequate data for analysis in 16 boys (baseline age 10.9 to 13.9 years; Tanner Stage=1 to 4) and 12 girls (baseline age=11.2 to 13.7 years; Tanner Stage=3 to 4). Brain volumes were derived from T1-weighted (SPGR) images and dual-echo Fast Spin-Echo (FSE) images collected on a GE 3T scanner with an 8-channel phased-array head coil and analyzed by registration-based parcellation using the SRI24 atlas. The "independent" method required two inter-subject registrations: both baseline (MRI 1) to atlas and follow-up (MRI 2) to the atlas. The "sequential" method required one inter-subject registration, which was MRI 1 to the atlas, and one intra-subject registration, which was MRI 2 to MRI 1. Gray matter/white matter/CSF were segmented in both MRI-1 and MRI-2 using FSL FAST with tissue priors also based on the SRI24 atlas. Gray matter volumes were derived for 10 cortical regions, gray+white matter volumes for 5 subcortical structures, and CSF volumes for 4 ventricular regions and the cortical sulci. Across the 15 tissue regions, the coefficient of variation (CV) of change scores across individuals was significantly lower for the sequential method (CV=3.02), requiring only one inter-subject registration, than for the independent method (CV=9.43), requiring two inter-subject registrations. Volume change based on the sequential method revealed that total supratentorial and CSF volumes increased, while cortical gray matter volumes declined significantly (p<0.01) in anterior (lateral and medial frontal, anterior cingulate, precuneus, and parietal) but not posterior (occipital, calcarine) cortical regions. These volume changes occurred in all boys and girls who advanced a step in Tanner staging. Subcortical structures did not show consistent changes. Thus, longitudinal MRI assessment using robust registration methods is sufficiently sensitive to identify significant regional brain changes over a 7-month interval in boys and girls in early adolescence. Increasing the temporal resolution of the retest interval in longitudinal developmental studies could increase accuracy in timing of peak growth of regional brain tissue and refine our understanding of the neural mechanisms underlying the dynamic changes in brain structure throughout adolescence.

Topographic differences in the adolescent maturation of the slow wave EEG during NREM sleep

STUDY OBJECTIVES

Our ongoing longitudinal study has shown that NREM delta (1-4 Hz) and theta (4-8 Hz) power measured at C3 and C4 decrease by more than 60% between ages 11 and 17 years. Here, we investigate the age trajectories of delta and theta power at frontal, central, and occipital electrodes.

DESIGN

Baseline sleep EEG was recorded twice yearly for 6 years in 2 cohorts, spanning ages 9-18 years, with overlap at 12-15 years.

SETTING

Sleep EEG was recorded in the subjects' homes with ambulatory recorders.

PARTICIPANTS

Sixty-seven subjects in 2 cohorts, one starting at age 9 (n = 30) and one at age 12 years (n = 37).

MEASUREMENTS AND RESULTS

Sleep EEG recorded from Fz, Cz, C3, C4, and O1 was referred to mastoids. Visual scoring and artifact elimination was followed by FFT power analysis. Delta and theta EEG power declined steeply across this age range. The maturational trajectories of delta power showed a "back to front" pattern, with O1 delta power declining earliest and Fz delta power declining latest. Theta EEG power did not show this topographic difference in the timing of its decline. Delta, and to a lesser extent, theta power became frontally dominant in early adolescence.

CONCLUSIONS

We maintain our interpretation that the adolescent decline in EEG power reflects a widespread brain reorganization driven by synaptic pruning. The late decline in frontally recorded delta power indicates that plasticity is maintained in these circuits until a later age. Although delta and theta have similar homeostatic properties, they have different age and topographic patterns that imply different functional correlates.

Changes in sleep as a function of adolescent development

Adolescence is marked by dramatic changes in sleep. Older adolescents go to bed later, have an increased preference for evening activities, and sleep less than younger adolescents. This behavior change is driven by external factors, notably increased pressures from academic, social, and extracurricular activities and by biological circadian factors. There are also substantial changes in sleep architecture across adolescence, with dramatic declines in slow wave sleep, and slow wave activity (delta, ~ 0.5-4.5 Hz). These changes are associated with underlying changes in brain structure and organization, with a decrease in synaptic density likely underlying the reduction in high amplitude slow waveforms. While changes in sleep across adolescence are a normal part of development, many adolescents are getting insufficient sleep and are consequently, less likely to perform well at school, more likely to develop mood-related disturbances, be obese, and are at greater risk for traffic accidents, alcohol and drug abuse.

Adolescent changes in homeostatic regulation of EEG activity in the delta and theta frequency bands during NREM sleep

STUDY OBJECTIVES

Slow wave EEG activity in NREM sleep decreases by more than 60% between ages 10 and 20 years. Slow wave EEG activity also declines across NREM periods (NREMPs) within a night, and this decline is thought to represent the dynamics of sleep homeostasis. We used longitudinal data to determine whether these homeostatic dynamics change across adolescence.

DESIGN

All-night sleep EEG was recorded semiannually for 6 years.

SETTING

EEG was recorded with ambulatory recorders in the subjects' homes.

PARTICIPANTS

Sixty-seven subjects in 2 cohorts, one starting at age 9 and one starting at age 12 years.

MEASUREMENTS AND RESULTS

For NREM delta (1-4 Hz) and theta (4-8 Hz) EEG, we tested whether the proportion of spectral energy contained in the first NREMP changes with age. We also tested for age changes in the parameters of the process S exponential decline. For both delta and theta, the proportion of energy in the first NREMP declined significantly across ages 9 to 18 years. Process S parameters SWA(0) and TWA(0), respectively, represent slow wave (delta) activity and theta wave activity at the beginning of the night. SWA(0) and TWA(0) declined significantly (P < 0.0001) across ages 9 to 18.

CONCLUSIONS

These declines indicate that the intensity of the homeostatic or restorative processes at the beginning of sleep diminished across adolescence. We propose that this change in sleep regulation is caused by the synaptic pruning that occurs during adolescent brain maturation.