Pubertal changes in daytime sleepiness

Sleep EEG changes during adolescence: an index of a fundamental brain reorganization

Delta (1-4 Hz) EEG power in non-rapid eye movement (NREM) sleep declines massively during adolescence. This observation stimulated the hypothesis that during adolescence the human brain undergoes an extensive reorganization driven by synaptic elimination. The parallel declines in synaptic density, delta wave amplitude and cortical metabolic rate during adolescence further support this model. These late brain changes probably represent the final ontogenetic manifestation of nature's strategy for constructing nervous systems: an initial overproduction of neural elements followed by elimination. Errors in adolescent brain reorganization may cause mental illness; this could explain the typical age of onset of schizophrenia. Longitudinal studies of sleep EEG are enhancing our knowledge of adolescent brain maturation. Our longitudinal study of sleep EEG changes in adolescence showed that delta power, which may reflect frontal cortex maturation, begins its decline between ages 11 and 12 years and falls by 65% by age 17 years. In contrast, NREM theta power begins its decline much earlier. Delta and theta EEG frequencies are important to sleep theory because they behave homeostatically. Surprisingly, these brain changes are unrelated to pubertal maturation but are strongly linked to age. In addition to these (and other) maturational EEG changes, sleep schedules in adolescence change in response to a complex interaction of circadian, social and other influences. Our data demonstrate that the daytime sleepiness that emerges in adolescence is related to the decline in NREM delta as well as to altered sleep schedules. These longitudinal sleep data provide guideposts for studying cognitive and behavioral correlates of adolescent brain reorganization.

Reward-related brain function and sleep in pre/early pubertal and mid/late pubertal adolescents

PURPOSE

The onset of adolescence is a time of dramatic changes, including changes in sleep, and a time of new health concerns related to increases in risk-taking, sensation seeking, depression, substance use, and accidents. As part of a larger study examining puberty-specific changes in adolescents' reward-related brain function, the current article focuses on the relationship between functional neuroimaging measures of reward and measures of sleep.

METHODS

A total of 58 healthy participants 11-13 years of age completed a functional magnetic resonance imaging scan using a guessing task with monetary rewards and 4 days of at-home actigraphy and self-reported sleep ratings. Sleep variables included actigraph measures of mean weekend minutes asleep, sleep onset time, and sleep offset time, as well as self-reported sleep quality.

RESULTS

During reward anticipation, less activation in the caudate (part of the ventral striatum) was associated with fewer minutes asleep, later sleep onset time, and lower sleep quality. During reward outcome, less caudate activation was associated with later sleep onset time, earlier sleep offset time, and lower sleep quality.

CONCLUSIONS

It has been hypothesized that adolescents' low reactivity in reward-related brain areas could lead to compensatory increases in reward-driven behavior. This study's findings suggest that sleep could contribute to such behavior. Because decreased sleep has been associated with risky behavior and negative mood, these findings raise concerns about a negative spiral whereby the effects of puberty and sleep deprivation may have synergistic effects on reward processing, contributing to adolescent behavioral and emotional health problems.

Psychosocial, mechanical, and metabolic factors in adolescents' musculoskeletal pain in multiple locations: a cross-sectional study

Recent studies indicate that adolescents often experience musculoskeletal pains in two or more body locations. However, previous studies have mainly focused on localized pains, and the determinants of multiple musculoskeletal pains in adolescents are not well known. The present study was set to evaluate the role of psychosocial, mechanical, and metabolic factors in adolescents' musculoskeletal pains in multiple locations. The study population consisted of the 1986 Northern Finland Birth Cohort; 15- to 16-year-old adolescents (n=6986), who responded to a mailed questionnaire in 2001. We assessed the associations of emotional and behavioral problems, physical activity, sitting time, sleeping time, overweight and smoking with musculoskeletal pains using multinomial logistic regression. Multiple pains were common, 23% of boys and 40% of girls reported feeling pain in at least three locations over the past 6 months. These pains were not only associated with anxious/depressed symptoms, withdrawn/depressed symptoms, somatic complaints, rule-breaking and aggressive behavior, social problems, thought and attention problems, but also with high physical activity level, long sitting time, short sleeping time and smoking, among both boys and girls. In addition, pain in three to four locations associated with overweight in girls. A high number of psychosocial, mechanical and metabolic factors associated strongly with multiple pains. In conclusion, multiple musculoskeletal pains were strongly associated with psychosocial complaints, but also with mechanical and metabolic factors. Reported musculoskeletal pains in multiple locations in adolescence may have both peripheral (trauma, decreased regenerative ability) and central (sensitivity) causes.

Adolescent changes in the homeostatic and circadian regulation of sleep

Sleep deprivation among adolescents is epidemic. We argue that this sleep deprivation is due in part to pubertal changes in the homeostatic and circadian regulation of sleep. These changes promote a delayed sleep phase that is exacerbated by evening light exposure and incompatible with aspects of modern society, notably early school start times. In this review of human and animal literature, we demonstrate that delayed sleep phase during puberty is likely a common phenomenon in mammals, not specific to human adolescents, and we provide insight into the mechanisms underlying this phenomenon.

Relationships among sleepiness, sleep time, and psychological functioning in adolescents

OBJECTIVE

This study examined associations among adolescent sleepiness, sleep duration, variability in sleep duration, and psychological functioning (symptoms of anxiety, depression, externalizing behaviors, and perceived health).

METHODS

This was a cross-sectional analysis of data from a community-based cohort study of sleep and health. Participants were 247 adolescents (48.6% female, 54.3% ethnic minority, mean age of 13.7 years). Sleep duration and variability in sleep duration were measured by actigraphy and sleepiness was measured by adolescent questionnaire. Primary outcomes were measured by parent, teacher, and adolescent questionnaires.

RESULTS

Sleepiness was associated with higher scores on measures of anxiety (Adjusted partial r(2) = .28, p < .001), depression (Adjusted partial r(2) = .23, p < .001), and perceived health (indicating more negative outcomes) (Adjusted partial r(2) = .19, p < .01). Significant associations between sleep duration or variability in sleep duration with psychological variables were not found.

CONCLUSIONS

Findings highlight the inter-relationships between sleepiness and psychological functioning and the potential importance of addressing sleepiness in health and psychological evaluations of adolescents.

The onset of puberty: effects on the psychophysiology of defensive and appetitive motivation

We examined puberty-specific effects on affect-related behavior and on the psychophysiology of defensive and appetitive motivation while controlling for age. Adolescents (N = 94, ages = 12 and 13 years) viewed 75 pictures (International Affective Picture System: pleasant, neutral, and aversive) while listening to auditory probes. Startle response and postauricular (PA) reflex were collected as measures of defensive and appetitive motivation, respectively. Pubertal status and measures of anxiety/stress reaction and sensation/thrill seeking were obtained. Mid-/late pubertal adolescents showed enhanced startle amplitude across all picture valences. A Puberty x Valence interaction revealed that mid-/late pubertal adolescents showed appetitive potentiation of the PA, whereas pre-/early pubertal adolescents showed no modulation of the PA reflex. Mid-/late pubertal adolescents also scored significantly higher on measures of sensation/thrill seeking than did their pre-/early pubertal peers and puberty moderated the association between psychophysiology and behavioral measures, suggesting that it plays a role in reorganizing defensive and appetitive motivational systems.

Consequences of the timing of menarche on female adolescent sleep phase preference

Most parents experience their children's puberty as a dramatic change in family life. This is not surprising considering the dynamics of physical and psychosocial maturation which occur during adolescence. A reasonable question, particularly from the parents' perspective, is: when does this vibrant episode end and adulthood finally start? The aim of the present study was to assess the relationship between puberty and the changes in sleep phase preferences during female maturation and adulthood by a cross-sectional survey. The results from 1'187 females aged 5 to 51 years based on self-report measures of sleep preferences on weekdays and on free days as well as the occurrence of menarche, show that in contrast to prepubertal children, adolescent females exhibit a striking progression in delaying their sleep phase preference until 5 years after menarche. Thereafter, the sleep phase preference switches to advancing. The current study provides evidence that a clear shift in sleep-wake cycles temporally linked to menarche heralds the beginning of "adult-like" sleep-wake behaviour in women and can be used as a (chrono)biological marker for the onset of adulthood.

Sleepless in adolescence: prospective data on sleep deprivation, health and functioning

We estimate prevalence, incidence and persistence of short sleep or sleep deprivation in a two wave cohort study of 4175 youths 11-17 years old at baseline and 3134 of these a year later. Data were collected using computer interviews and questionnaires. Sleep deprivation was defined as 6h or less per night during the past 4 weeks. Weighted logistic regression procedures were employed to calculate prevalence, incidence, persistence/chronicity, and odds ratios. Prevalence rates and rates of persistence suggest sleep deprivation is highly prevalent and chronic. Multivariate analyses indicate that short sleep increases risk across multiple domains of dysfunction, suggesting pervasive deleterious effects. The broad impact of sleep deprivation and its pervasiveness suggests interventions will need to focus on multilevel changes to increase sleep time and reduce the negative impact of sleep deprivation among adolescents.

The regulation of sleep and arousal: Development and psychopathology

Throughout early development, a child spends more time asleep than in any waking activity. Yet, the specific role of sleep in brain maturation is a complete mystery. In this article, the developmental psychobiology of sleep regulation is conceptualized within the context of close links to the control of arousal, affect, and attention. The interactions among these systems are considered from an ontogenetic and evolutionary biological perspective. A model is proposed for the development of sleep and arousal regulation with the following major tenets:

1. Sleep and vigilance represent opponent processes in a larger system of arousal regulation.

2. The regulation of sleep, arousal, affect, and attention overlap in physiological, neuroanatomical, clinical, and developmental domains.

3. Complex interactions among these regulatory systems are modulated and integrated in regions of the prefrontal cortex (PFC).

4. Changes at the level of PFC underlie maturational shifts in the relative balance across these regulatory systems (such as decreases in the depth/length of sleep and increased capacity for vigilance and attention), which occur with normal development.

5. The effects of sleep deprivation (including alterations in attention, emotions, and goal-directed behaviors) also involve changes at the level of PFC integration across regulatory systems.

This model is then discussed in the context of developmental pathology in the control of affect and attention, with an emphasis on sleep changes in depression.

Pubertal development: correspondence between hormonal and physical development

Puberty is advanced by sex hormones, yet it is not clear how it is best measured. The interrelation of multiple indices of puberty was examined, including the Pubertal Development Scale (PDS), a picture-based interview about puberty (PBIP), and a physical exam. These physical pubertal measures were then associated with basal hormones responsible for advancing puberty. Participants included 160 early adolescents (82 boys). Puberty indices were highly correlated with each other. The physical exam stages correlated well with boys' and girls' testosterone and dehydroepiandrosterone and less so with girls' estradiol. The PDS and PBIP were similarly related to basal hormones. Self-report may be adequate when precise agreement is unnecessary. Multiple measures of puberty are viable options, each with respective strengths.

The sleep patterns and problems of clinically anxious children

Childhood sleep problems have been associated with a range of adverse cognitive and academic outcomes, as well as increased impulsivity and emotional disorders such as anxiety and depression. The aim of the study was to examine subjective reports of sleep-related problems in children with anxiety disorders during school and weekend nights. Thirty-seven children with clinically-diagnosed anxiety disorders and 26 non-clinical children aged 7-12 years completed an on-line sleep diary to track sleep patterns across school nights and weekend nights. Anxious children reported going to bed significantly later (p=0.03) and had significantly less sleep (p=0.006) on school nights compared to non-anxious children. No significant differences in sleep onset latency, number of awakenings or time awake during the night, daytime sleepiness, or fatigue were found between the two groups. On the weekends, anxious children fell asleep quicker and were less awake during the night than on weeknights. School-aged anxiety disordered children showed a sleep pattern that differs from their non-anxious peers. Although the mean 30 min less sleep experienced by anxious children may initially seem small, the potential consequences on daytime performance from an accumulation of such a sleep deficit may be significant, and further investigation is warranted.

Longitudinal study of maternal report of sleep problems in children with prenatal exposure to cocaine and other drugs

Sleep data were collected by maternal report in a prospective longitudinal follow up of cocaine-exposed and unexposed children. There were 139 participants: 23 with no prenatal drug exposure, 55 exposed to cocaine alone or in combination with other drugs, and 61 exposed to drugs other than cocaine. Characteristics differed between exposure groups including birth size, caretaker changes, maternal socioeconomic status, and postnatal drug use. Compared to those with no drug exposure, children with prenatal drug exposure other than cocaine experienced greater sleep problems (p = .026). Prenatal nicotine exposure was a unique predictor of sleep problems (p = .048). Early sleep problems predicted later sleep problems (all ps < .01). Together, these preliminary findings suggest possible neurotoxic sleep effects that persist over time. Larger studies, however, need to be conducted that better control for potential postnatal confounding factors.

Insomnia of childhood

PURPOSE OF REVIEW

Insomnia is a major public health problem and is the most common sleep disturbance in both adults and children. The causes of sleeplessness are age-dependent and have potentially enormous effects on cognitive development, behavior, family dynamics, and the metabolic health of children. Here we review the epidemiology, cause, pathophysiology, and clinical approach to pediatric insomnia.

RECENT FINDINGS

Normal sleep is crucial for brain function, behavior, and normal metabolism. Consistently, sleep loss has been linked to behavioral and attention problems, impaired learning and memory, obesity, and psychiatric disorders. The neurological mechanisms that govern sleep initiation and maintenance are poorly understood. The types of insomnia are age-dependent and can occur as primary disorders, or in the context of another primary sleep disorder such as restless legs syndrome, or secondary to another underlying medical condition. Children with chronic diseases and especially children with neurodevelopmental disorders are at particular risk of insomnia.

SUMMARY

Pediatric insomnia is common and is a source of potential psychophysiological stress to both children and their caregivers. The causes of insomnia are various. Pediatricians should have a working knowledge of the causes of sleeplessness in order to promptly curtail the chronic effects of sleep loss and effectively screen for underlying, potentially treatable disorders.

Pediatric narcolepsy

Narcolepsy is a disabling disease with a prevalence of 0.05%. It is characterized by excessive daytime sleepiness, cataplexy, sleep paralysis, hypnogogic hallucinations, automatic behavior, and disrupted nocturnal sleep. The presentation can be very variable, making diagnosis difficult. Loss of hypocretin containing neurons in the lateral hypothalamus has been noted in autopsy studies, and the cerebrospinal fluid level of hypocretin is reduced in patients with narcolepsy with cataplexy. New treatment options are available for the many symptoms of this disease. Early recognition and treatment can greatly improve the quality of life of patients with narcolepsy. A detail review of the epidemiology, pathophysiology, and management of narcolepsy in children is presented.

A practical approach to circadian rhythm sleep disorders

Circadian rhythm sleep disorders are common in clinical practice. The disorders covered in this review are delayed sleep phase disorder, advanced sleep phase disorder, free-running, irregular sleep-wake rhythm, jet lag disorder and shift work disorder. Bright light treatment and exogenous melatonin administration are considered to be the treatments of choice for these circadian rhythm sleep disorders. Circadian phase needs to be estimated in order to time the treatments appropriately. Inappropriately timed bright light and melatonin will likely worsen the condition. Measurements of core body temperature or endogenous melatonin rhythms will objectively assess circadian phase; however, such measurements are seldom or never used in a busy clinical practice. This review will focus on how to estimate circadian phase based on a careful patient history. Based on such estimations of circadian phase, we will recommend appropriate timing of bright light and/or melatonin in the different circadian rhythm sleep disorders. We hope this practical approach and simple recommendations will stimulate clinicians to treat patients with circadian rhythm sleep disorders.

Are adolescents chronically sleep-deprived? An investigation of sleep habits of adolescents in the Southwest of Germany

BACKGROUND

Adolescent sleep receives increasing attention. Several studies have shown that adolescents generally do not sleep enough. This survey assessed adolescents' sleep patterns, and results were compared with sleep logs.

METHODS

A total of 818 students aged 12-18 attending three different school types were asked to complete a questionnaire, adapted from the 'School Sleep Habits Survey', and filled in a sleep protocol over 2 weeks. Information on sleep patterns and demographic data were obtained additionally.

RESULTS

A total of 601 students completed the questionnaire (i.e. 73.5% return rate), 55.1% female and 44.9% male. Average sleep duration during the week amounted to 8.04+/-0.89 h and 9.51+/-1.65 h on weekends. Sleep duration times on school days decreased from an average 8.64+/-0.83 h for the age category 12-13 years to 7.83+/-0.72 h for students above 16 years. 91.6% of all students slept less than 9.2 h per night during the week. Data from the 153 returned sleep logs showed even lower sleep times (7.75+/-0.82 h for school nights).

CONCLUSIONS

The main hypothesis that students sleep on average considerably less than the recommended 9 h during weekdays was confirmed. Bedtimes changed throughout the week with the latest on Friday and Saturday nights and the least sleep around midweek. There were no significant group differences regarding school type and environment (rural vs. urban). Interestingly, the majority reported only little daytime sleepiness and no impaired performance. Results regarding the consequences of chronic sleep deprivation in the literature are inconclusive. The impact on physiological parameters, especially metabolic functions, requires further investigations.

Sleep patterns among rural Chinese twin adolescents

OBJECTIVE

To examine sleep patterns and influencing factors (age, gender, Tanner Stage, weekday vs. weekend, and pre-sleep activity) among rural Chinese adolescents.

METHODS

This is a prospective study among 621 adolescents aged 11-20 years (341 males) using both a questionnaire and sleep diary to obtain bedtime, wake-up time, sleep latency, and total sleep time (TST).

RESULTS

The median TST was 8.6h on weekdays and 9.4h on weekends. Despite absence of late night social pressure and computers, a U-shaped TST pattern was observed across age and Tanner Stage, with a nadir around age 15-16 years or Tanner IV. Bedtimes became progressively later with age and Tanner Stage, while wake-up time was considerably earlier for school students or up to Tanner IV. Later wake-up times and longer TST on weekends were seen in school students, but not in non-school adolescents (>17 years). Pre-sleep activity, like reading or studying, was related to later bedtime, earlier wake-up time, and shorter TST in both genders.

CONCLUSIONS

Age, Tanner Stage, and pre-sleep activity affected sleep patterns in this sample of rural Chinese adolescents. Later bedtime coupled with earlier wake-up time associated with academic demand appear to be important contributors to sleep loss among school students.

The sleepy adolescent: causes and consequences of sleepiness in teens

The majority of adolescents do not obtain the recommended amount of sleep, resulting in significant daytime sleepiness. For most adolescents, insufficient sleep results from the interaction between intrinsic factors such as puberty and extrinsic factors such as school start times. Insufficient sleep and sleepiness impact all areas of adolescent functioning, including academic, psychological and behavioural, which underscores the importance of evaluating sleepy adolescents. While polysomnography is required for the diagnosis of certain sleep disorders, causes of sleepiness are generally best identified with a detailed sleep history and daily sleep diary. The management of sleep problems in adolescents involves treating any underlying sleep disorders, increasing total sleep time and improving other environmental factors that impact sleep. Recognition and management of insufficient sleep and sleepiness is important for the health and functioning of adolescents.

Sleep-wake patterns and sleep disturbance among Hong Kong Chinese adolescents

STUDY OBJECTIVES

To determine sleep-wake patterns and evaluate sleep disturbance in Hong Kong adolescents; to identify factors that are associated with sleep disturbance; and to examine the relationship of sleep-wake variables and academic performance.

DESIGN AND SETTING

A school-based cross-sectional survey.

PARTICIPANTS

Sample included 1629 adolescents aged 12 to 19 years.

MEASUREMENTS AND RESULTS

Self-report questionnaires, including sleep-wake habit questionnaire, Sleep Quality Index, Morningness/ Eveningness scale, Epworth Sleepiness Scale, Perceived Stress Scale, academic performance, and personal data were administered. The average school-night bedtime was 23:24, and total sleep time was 7.3 hr. During weekends, the average bedtime and rise time was delayed by 64 min and 195 min, respectively. The prevalence of sleep disturbances occurring > or = 3 days per week in the preceding 3 months were: difficulty falling asleep (5.6%), waking up during the night (7.2%), and waking up too early in the morning (10.4%). The prevalence of > or = 1 of these three symptoms was 19.1%. Stepwise regression analyses revealed that circadian phase preference was the most significant predictor for school night bedtime, weekend oversleep, and daytime sleepiness. Perceived stress was the most significant risk factor for sleep disturbance. Students with marginal academic performance reported later bedtimes and shorter sleep during school nights, greater weekend delays in bedtime, and more daytime sleepiness than those with better grades.

CONCLUSION

The prevalence of sleep deprivation and sleep disturbance among Hong Kong adolescents is comparable to those found in other countries. An intervention program for sleep problems in adolescents should be considered.

Sleep disordered breathing and daytime sleepiness are associated with poor academic performance in teenagers. A study using the Pediatric Daytime Sleepiness Scale (PDSS)

STUDY OBJECTIVES

Inadequate sleep and sleep disordered breathing (SDB) can impair learning skills. Questionnaires used to evaluate sleepiness in adults are usually inadequate for adolescents. We conducted a study to evaluate the performance of a Spanish version of the Pediatric Daytime Sleepiness Scale (PDSS) and to assess the impact of sleepiness and SDB on academic performance.

DESIGN

A cross-sectional survey of students from 7 schools in 4 cities of Argentina.

MEASUREMENTS

A questionnaire with a Spanish version of the PDSS was used. Questions on the occurrence of snoring and witnessed apneas were answered by the parents. Mathematics and language grades were used as indicators of academic performance.

PARTICIPANTS

The sample included 2,884 students (50% males; age: 13.3 +/- 1.5 years)

RESULTS

Response rate was 85%; 678 cases were excluded due to missing data. Half the students slept <9 h per night on weekdays. The mean PDSS value was 15.74 +/- 5.93. Parental reporting of snoring occurred in 511 subjects (23%); snoring was occasional in 14% and frequent in 9%. Apneas were witnessed in 237 cases (11%), being frequent in 4% and occasional in 7%. Frequent snorers had higher mean PDSS scores than occasional or nonsnorers (18 +/- 5, 15.7 +/- 6 and 15.5 +/- 6, respectively; P < 0.001). Reported snoring or apneas and the PDSS were significant univariate predictors of failure and remained significant in multivariate logistic regression analysis after adjusting for age, sex, body mass index, specific school attended, and sleep habits.

CONCLUSIONS

Insufficient hours of sleep were prevalent in this population. The Spanish version of the PDSS was a reliable tool in middle-school-aged children. Reports of snoring or witnessed apneas and daytime sleepiness as measured by PDSS were independent predictors of poor academic performance.

Neurocognitive and behavioral morbidity in children with sleep disorders

PURPOSE OF REVIEW

This review examines in detail progress made regarding our understanding of the presence and pathophysiology of cognitive and behavioral morbidities among children with sleep disorders in general. Particular focus is given to pediatric obstructive sleep apnea.

RECENT FINDINGS

In recent years, increased awareness of the morbid consequences of respiratory sleep disturbances in children has emerged. Evidence suggesting a causal association of intermittent hypoxia and sleep fragmentation with alterations in memory, attention, and intelligence has accumulated. Research has also identified a link between sleep disorders, and problematic and hyperactive behaviors and mood disturbances. Furthermore, there is considerable inter-individual variability in the presence and magnitude of neurobehavioral morbidity at any given level of disease severity. This further suggests that, in addition to the disease per se, both genetic (individual susceptibility) and environmental modifiers play a role in determining morbidity.

SUMMARY

A more individually tailored approach to detecting morbidity associated with sleep disorders in children, employing biomarkers and gene-related single nucleotide polymorphisms, may ultimately be required to allow more rational prioritization of treatment.

Middle school start times: the importance of a good night's sleep for young adolescents

With the onset of adolescence, teenagers require 9.2 hr of sleep and experience a delay in the timing of sleep. In the "real world" with early school start times, however, they report less sleep, striking differences between their school-weekend sleep schedules, and significant daytime sleepiness. Prior studies demonstrated that high schoolers with later school starts do not further delay bedtime but obtain more sleep due to later wake times. This study examined sleep-wake patterns of young adolescents attending urban, public middle schools with early (7:15 a.m.) versus late (8:37 a.m.) start times. Students (N = 205) were assessed at 2 time periods. Students at the late-starting school reported waking up over 1 hr later on school mornings and obtaining 50 min more sleep each night, less sleepiness, and fewer tardies than students at the early school. All students reported similar school-night bedtime, sleep hygiene practices, and weekend sleep schedules.

The increase in longitudinally measured sleepiness across adolescence is related to the maturational decline in low-frequency EEG power

OBJECTIVES

A changing sleep schedule that reduces sleep duration is thought to produce the increasing daytime sleepiness of adolescents. We tested the hypothesis that adolescent daytime sleepiness also results from adolescent brain maturational processes indexed by declining delta electroencephalographic (EEG) activity.

DESIGN

Data are from the first 3 years of a semilongitudinal study of EEG changes in adolescence. All-night EEG was recorded semiannually.

SETTING

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

PARTICIPANTS

Thirty-one subjects were 9 years old (cohort C9), and 38 subjects were 12 years old (cohort C12) at the start of the study.

MEASUREMENTS

EEG power density (power/minute) was calculated for the first 5 hours of non-rapid eye movement sleep. Subjects rated sleepiness on a modified Epworth Sleepiness Scale. Habitual sleep schedules were assessed with self-reports and actigraphy.

RESULTS

In C9 subjects, sleepiness increased slightly and was related only to age. In C12 subjects, the increase in subjective sleepiness was related to changes in age, bedtime, time in bed, and a wide frequency range of EEG power density. Sleepiness was not related to rise time, non-rapid eye movement sleep duration, rapid eye movement sleep duration, or total sleep time. With sleep schedule measures statistically controlled, the increase in sleepiness in the C12 group was strongly related to declining delta power density and, unexpectedly, even more strongly related to declining theta power density.

CONCLUSIONS

The data support our hypothesis that, independent of sleep schedule changes, increasing adolescent daytime sleepiness is related to brain maturational changes indexed by declining EEG power. Our working hypothesis is that the declines in delta and theta power are correlates of an adolescent synaptic pruning that reduces waking arousal levels.

Daytime sleepiness and associated factors in Japanese school children

OBJECTIVE

To examine daytime sleepiness and sleepiness interrelationship with sleep-wake patterns, eating habits, physical activity, and TV/video game time.

STUDY DESIGN

A cross-sectional survey with 9,261 school children (mean age of 12.8 years) from 93 junior high schools in Toyama prefecture, Japan.

RESULTS

The main outcome measures were daytime sleepiness during schooldays and sleepiness interrelationship with sleep-wake patterns, eating habits, physical activity, and visual media use. A total of 2,328 children (25.2%) reported sleepiness almost always and 4,401 (47.6%) sleepiness often. Regarding sex difference, a higher proportion of girls reported sleepiness in comparison to boys (79% vs 66%, P < .001). Higher body mass index values were associated with the presence of sleepiness. In girls with preferences for daily snack (versus those who reported no snack) sleepiness presented significantly (P < .001) higher values. Reduced sleep time was significantly associated with sleepiness. The prevalence of sleepiness did not significantly differ among groups who had 7.5 hours sleep or more. A dose-response relation was found between sleepiness and sleep disturbances, physical activity, and media use time.

CONCLUSIONS

Sleep insufficiency represents a main cause for daytime sleepiness in Japanese junior high school children. Proper sleep habits, high physical activity level, and limited TV viewing time should be promoted among school children.

Sleep and the body mass index and overweight status of children and adolescents

Associations between sleep and the body mass index (BMI) and overweight status of children and adolescents were estimated using longitudinal data from a nationally representative sample of 2,281 children aged 3-12 years at baseline. Controlling for baseline BMI, children who slept less, went to bed later, or got up earlier at the time of the first assessment had higher BMIs 5 years later and were more likely to be overweight. Child age moderated the relationship between bedtime and BMI. In addition, the study reports nationally representative data on the sleep habits of American children aged 3-18 years. This study underscores the likely importance of sleep on children's physical health and suggests that sleep is important for understanding childhood weight problems.

Protective and risk factors in health-enhancing behavior among adolescents in China and the United States: does social context matter?

An explanatory model of adolescent health-enhancing behavior based on protective and risk factors at the individual level and in 4 social contexts was used in a study of school-based samples from the People's Republic of China (n = 1,739) and the United States (n = 1,596). A substantial account of variation in health-enhancing behavior--and of its developmental change over time--was provided by the model for boys and girls, and for the 3 grade cohorts, in both samples. In both samples, social context protective and risk factors accounted for more unique variance than did individual-level protective and risk factors, and context protection moderated both contextual and individual-level risk. Models protection and controls protection were of particular importance in the explanatory account.

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

Two dramatic phenomena of human adolescence are sexual maturation and a steep decline in the delta EEG of non-rapid eye movement (NREM) sleep. It has long been speculated that these developmental changes are causally related. Here, we present the first longitudinal data on this issue. Cohorts of 9- and 12-year-old children (n = 31, 38) were studied with in-home sleep EEG recordings at 6-mo intervals over 2 years. Pubertal (Tanner) stage, height, and weight were obtained at each time point. NREM delta power density (DPD) did not change significantly over ages 9-11 years, and its level did not differ in boys and girls. DPD declined by 25% between ages 12 and 14 years. This decline was parallel in the two sexes, but levels were lower in girls, suggesting that their DPD decline began earlier. Mixed effect analyses demonstrated that DPD was strongly related to age with Tanner stage, height, weight and body mass index controlled but that none of these measures of physical and sexual development was related to DPD with age controlled. NREM delta is the sleep EEG component homeostatically related to prior waking duration and the intensity of waking brain activity. We hypothesize that the DPD decline is caused by age-programmed synaptic pruning that decreases waking brain metabolic rate. This reduced rate would decrease the "substrate" for delta homeostasis. Whether or not this interpretation proves correct, these longitudinal data demonstrate that the delta decline in adolescence reflects brain processes that are not predicted by physical growth or sexual maturation.

Melatonin treatment in adolescents with delayed sleep phase syndrome

This retrospective study describes the effects of long-term treatment with melatonin in 33 adolescents (age range, 10-18 years) with delayed sleep phase syndrome (DSPS). Patients were treated with oral melatonin, 3 to 5 mg/day for an average period of 6 months. During the treatment, sleep onset was advanced and sleep duration was longer. Treatment was also associated with a decrease in the proportion of patients reporting school difficulties. No adverse effects of melatonin were noted. This study indicates that long-term treatment with melatonin can be beneficial for adolescents with DSPS in terms of sleep-wake schedule and school performance.

Gonadal hormone effects on entrained and free-running circadian activity rhythms in the developing diurnal rodent Octodon degus

The slowly maturing, long-lived rodent Octodon degus (degu) provides a unique opportunity to examine the development of the circadian system during adolescence. These studies characterize entrained and free-running activity rhythms in gonadally intact and prepubertally gonadectomized male and female degus across the first year of life to clarify the impact of sex and gonadal hormones on the circadian system during adolescence. Gonadally intact degus exhibited a delay in the phase angle of activity onset (Psi(on)) during puberty, which reversed as animals became reproductively competent. Gonadectomy before puberty prevented this phase delay. However, the effect of gonadal hormones during puberty on Psi(on) does not result from changes in the period of the underlying circadian pacemaker. A sex difference in Psi(on) and free-running period (tau) emerged several months after puberty; these developmental changes are not likely to be related, since the sex difference in Psi(on) emerged before the sex difference in tau. Changes in the levels of circulating hormones cannot explain the emergence of these sex differences, since there is a rather lengthy delay between the age at which degus reach sexual maturity and the age at which Psi(on) and tau become sexually dimorphic. However, postnatal exposure to gonadal hormones is required for sexual differentiation of Psi(on) and tau, since these sex differences were absent in prepubertally gonadectomized degus. These data suggest that gonadal hormones modulate the circadian system during adolescent development and provide a new model for postpubertal sexual differentiation of a central nervous system structure.

Neurocognitive dysfunction in children with sleep disorders

It is well known that adults with sleep disturbances frequently exhibit a wide range of neurocognitive decrements, and that these deficits are potentially reversible with effective treatment. However, the consequences of respiratory sleep disturbances on neurocognitive function in children have only recently been evaluated, and suggest a strong causal association between the episodic hypoxia and sleep fragmentation that characterize the disease and the emergence of reduced memory, attention and intelligence as well as a link to problematic and hyperactive behaviours and mood disturbances. This article takes a critical look at the current literature on these issues, reviews the major findings and discusses such findings in conjunction with those derived from pertinent animal models.

"Sleepiness" is serious in adolescence: two surveys of 3235 Canadian students

BACKGROUND

Evidence is growing that sleep problems in adolescents are significant impediments to learning and negatively affect behaviour, attainment of social competence and quality of life. The objectives of the study were to determine the level of sleepiness among students in high school, to identify factors to explain it, and to determine the association between sleepiness and performance in both academic and extracurricular activities

METHODS

A cross-sectional survey of 2201 high school students in the Hamilton Wentworth District School Board and the Near North District School Board in Ontario was conducted in 1998/9. A similar survey was done three years later involving 1034 students in the Grand Erie District School Board in the same Province. The Epworth Sleepiness Scale (ESS) was used to measure sleepiness and we also assessed the reliability of this tool for this population. Descriptive analysis of the cohort and information on various measures of performance and demographic data were included. Regression analysis, using the generalised estimating equation (GEE), was utilized to investigate factors associated with risk of sleepiness (ESS>10).

RESULTS

Seventy per cent of the students had less than 8.5 hours weeknight sleep. Bedtime habits such as a consistent bedtime routine, staying up late or drinking caffeinated beverages before bed were statistically significantly associated with ESS, as were weeknight sleep quantity and gender. As ESS increased there was an increase in the proportion of students who felt their grades had dropped because of sleepiness, were late for school, were often extremely sleepy at school, and were involved in fewer extracurricular activities. These performance measures were statistically significantly associated with ESS. Twenty-three percent of the students felt their grades had dropped because of sleepiness. Most students (58-68%) reported that they were "really sleepy" between 8 and 10 A.M.

CONCLUSION

Sleep deprivation and excessive daytime sleepiness were common in two samples of Ontario high school students and were associated with a decrease in academic achievement and extracurricular activity. There is a need to increase awareness of this problem in the education and health communities and to translate knowledge already available to strategies to address it.

Associations between sleep and cortisol responses to stress in children and adolescents: a pilot study

A growing body of animal and human research suggests reciprocal associations between sleep and activity of the hypothalamic pituitary adrenocortical (HPA) axis. However, few studies have examined associations between sleep and stress-induced cortisol responses in children and adolescents. This pilot study examined associations among 3 sleep parameters (sleep-wake behavior problems, daytime sleepiness, sleep quantity) and cortisol responses to stress in 31 participants ages 10 to 17 (15 males, 16 females). During a "rest" session in which participants habituated to the laboratory, daytime sleepiness, sleep-wake behavior problems, and sleep quantity were assessed using a modified Sleep Habits Survey. On a separate day, participants completed a laboratory stress session involving 3 performance stressors. Salivary cortisol was collected during baseline, stress, and recovery periods. Significant associations between participant reported sleep-wake behavior problems and cortisol reactivity were found, with greater sleep-wake behavior problems associated with decreased cortisol responses. No associations emerged between sleep quantity and cortisol responses to stress; daytime sleepiness showed a trend toward an effect on cortisol reactivity. Although preliminary, results suggest there may be important influences of sleep quality but not quantity on HPA regulation and responses to daytime stressors in children and adolescents, and further study is warranted.

Sleep and risk-taking behavior in adolescents

The primary purpose of this study was to examine the relationship between adolescents' sleep-wake patterns and risk-taking behavior. A second goal was to replicate the results obtained by Wolfson and Carskadon (1998) regarding adolescents' sleep habits. Three hundred eighty-eight adolescents (217 males, 171 females) completed the Sleep Habits Survey and the Youth Risk Behavior Survey. The results indicated that adolescents who reported longer weekend delay and higher levels of sleep problems also reported significantly higher levels of risk-taking behaviors, and students' weekend delay was also related to their academic performance in this sample. As in the sample studied by Wolfson and Carskadon (1998), the adolescents in this study exhibited changes in both weekday and weekend sleep habits across grade/age. However in the present study, only school-night total sleep time and weekend delay were related to adolescents' daytime functioning, with no significant relationships being found between weekend oversleep and daytime functioning. This provides partial support for the findings of Wolfson and Carskadon (1998). Overall, sleep-wake patterns were found to relate to risk-taking behavior during adolescence in this study.

Prevalence and correlates of excessive daytime sleepiness in high school students in Korea

The purpose of the present study was to determine the prevalence of excessive daytime sleepiness (EDS) and its associations with sleep habits, sleep problems, and school performance in high school students in South Korea. A total of 3871 students (2703 boys and 1168 girls with a mean age of 16.8 years and 16.9 years, respectively) aged 15-18 years in the 11th grade of high school completed a questionnaire that contained items about individual sociodemographic characteristics, sleep habits, and sleep-related problems. The overall prevalence of EDS was 15.9% (14.9% for boys and 18.2% for girls). Mean reported total sleep time was similar in EDS and non-EDS (6.4 +/- 1.6 and 6.4 +/- 1.3 h/day, respectively). The increased risk of EDS was related to perceived sleep insufficiency (P < 0.001), teeth grinding > or = 4 days/week (P < 0.001), witnessed apnea > or = 1-3 days/week (P < 0.01), nightmares > or = 4 days/week (P < 0.05), low school performance (P < 0.01), and two or more insomnia symptoms (P < 0.05). Students with low school performance had a 60% excess in the odds of EDS compared to those whose school performance was high. These findings suggest that EDS is associated with multiple sleep-related factors in adolescents. Whether interventions to modify associated correlates can alter EDS warrants consideration, especially because it may also improve academic performance in high school students.

Teen at work: the burden of a double shift on daily activities

The purpose of this study was to the evaluate time spent by working and nonworking adolescents on daily activities (work, home duties, school, transportation, other activities, leisure, sleep, and naps). Twenty-seven students, 8 male workers, 8 female workers, 5 male nonworkers, and 6 female nonworkers, ages 14-18 yrs participated in the study. They attended evening classes Monday-Friday (19:00-22:30h) in a public school in the city of São Paulo, Brazil. The students answered a comprehensive questionnaire on the characterization of their life, work, and health conditions. Simultaneously, they wore actigraphs (Ambulatory Monitoring, Inc.) and completed a diary of their daily activities (time spent at work, on home duties, commuting, leisure, other activities) for a minimum of 10 to a maximum of 17 consecutive days. The means of the variables were tested for differences by a two-factor (work and sex) ANOVA and Student-t test applied to pair-wise samples (weekdays and weekends). The average duration during weekdays of working time was 7 h 09 min and home duties 0 h 48 min. As for commuting time, there was a work effect [F(1,23) = 4.9; p = 0.04]; mean commuting time was 2 h 22 min for workers (males and females) and 1 h 25 min for nonworkers. There was a significant difference between workers and nonworkers [F(1,23) = 4.6; p = 0.04] regarding extra-cirricular class activities; workers spent a mean of 3 min/day on them as opposed to 1 h 14 min by nonworkers. The average daily time spent on leisure activities by workers was 6h 31 min; whereas, for nonworkers it was 7h 38min. Time spent in school amounted to 2h 47min for workers in comparison to 3h 22min by nonworkers. There was a significant work effect upon sleep [F(1,23)= 10.0; p <0.01]. The work effect upon nighttime sleep duration was significant [F(1,23)= 16.7; p <0.01]. Male workers showed a mean night sleep of 6 h 57 min and female workers 07h 15min. The average nighttime sleep duration for nonworkers was 9 h 06 min. There was a significant interactive effect between work and sex [F(1,23)= 5.6; p=0.03] for naps. Female workers showed took shortest nap on average (36 min; SD = 26 min), and female nonworkers the longest naps (1 h 45min; SD= 35min). Study and employment exert significant impact on the life and activities of high school students. Work affects sleep and nap duration plus the amount of time spent in school and other extra-curricular activities.

Subjective sleep disturbances in adolescents with chronic pain: relationship to daily functioning and quality of life

The purpose of this study was to examine the relationship between pain symptoms, daily functioning, health-related quality of life (HRQOL), and subjectively reported sleep disturbances in adolescents with chronic pain. Depressive symptoms were tested as a general risk factor for increased sleep problems. During routine subspecialty clinic visits, 86 adolescents (mean age, 14.75 years; 67% female) diagnosed with chronic headaches, juvenile idiopathic arthritis, or sickle cell disease completed measures to assess pain, sleep disturbances, functional disability, depression, and HRQOL. Across pain diagnoses, adolescents experienced similar sleep patterns and sleep behaviors with the exception of daytime sleepiness, which was higher in adolescents with headache compared to adolescents with sickle cell disease. Bivariate correlations showed low relationships between pain and sleep and moderate to high relationships between depressive symptoms, daily functioning, HRQOL, and sleep. In multivariate analyses, as hypothesized, depressive symptoms were predictive of the severity of sleep disturbances after controlling for the effect of all other demographic, pain, and functional impact variables. Results suggest that a relationship between the experience of recurrent and chronic pain and sleep disturbances exists for adolescents, and these sleep disturbances are linked to mood disturbances and reductions in daily functioning and quality of life. Sleep disturbances have been described in adult patients with chronic pain, but little is known about sleep in adolescents with chronic pain. This study examined the complex interrelationship between sleep, pain, mood, functioning, and HRQOL. Findings suggest that mood is strongly related to sleep and might share common pathophysiologic or behavioral origins in adolescents with chronic pain.

Excessive sleepiness in adolescents and young adults: causes, consequences, and treatment strategies

Adolescents and young adults are often excessively sleepy. This excessive sleepiness can have a profound negative effect on school performance, cognitive function, and mood and has been associated with other serious consequences such as increased incidence of automobile crashes. In this article we review available scientific knowledge about normal sleep changes in adolescents (13-22 years of age), the factors associated with chronic insufficient sleep, the effect of insufficient sleep on a variety of systems and functions, and the primary sleep disorders or organic dysfunctions that, if untreated, can cause excessive daytime sleepiness in this population.

Regional differences of the sleep electroencephalogram in adolescents

The sleep electroencephalogram (EEG) was recorded from anterior (Fz/Cz) and posterior (Pz/Oz) bipolar derivations in two developmental groups: 20 pre- or early pubertal (Tanner 1/2, mean age 11.4 +/- 1.1 years, 11 boys) and 20 late pubertal or mature adolescents (Tanner 4/5, 14.1 +/- 1.3 years, 8 boys). A sleep-state independent reduction of EEG power over almost the entire frequency range was present in Tanner 4/5 compared with Tanner 1/2 adolescents. Spectral characteristics of the sleep EEG yielded state- and frequency-dependent regional differences that were similar in both developmental groups. Anterior predominance of power in delta and sigma ranges occurred in non-rapid eye movement sleep. Rapid eye movement sleep EEG power was greater in low delta, alpha, and sigma ranges for the posterior derivation and in theta and beta ranges for the anterior derivation. The decay rate of the sleep homeostatic process--reflected by the exponential decline of the 2-Hz EEG power band across the sleep episode--did not differ for derivations or groups. These results indicate that the nocturnal dynamics of sleep homeostasis are independent of derivation and remain stable across puberty.

Age-related changes in sleep/wake patterns among Korean teenagers

INTRODUCTION

As children go through the transition from childhood to adolescence, many shifts occur in sleep/wake patterns related to intrinsic and extrinsic developmental changes. These shifts have been shown to result in corresponding shifts in sleep phase (later sleep onset) and sleep deprivation among teenagers in Western societies. However, the effect of these developmental changes on the sleep habits of Korean teenagers has not been analyzed. This study aims to quantify age-related changes in sleep/wake patterns among Korean teenagers and elucidate cultural and other factors causing these changes.

METHODS

The School Sleep Habits Survey was administered in homeroom classes to students in grades 5 to 12 (mean age: 13.7 +/- 2.4 years) selected via a 2-way stratification sampling method. The survey included items regarding usual sleep/wake patterns over the previous 2 weeks as well as measures of daytime sleepiness, sleep/wake-problem behavior, depressed mood, and morningness/eveningness.

RESULTS

A total of 1457 students (52.9% male) completed the survey. The higher the grade, the later bedtime was found to be on both school days and weekends. There was a similar relationship between increasing grade and earlier wake time on school days, but higher grades were associated with later wake time on weekends. Total sleep time decreased by approximately 3 hours on school nights and 1 hour on weekend nights from grades 5 to 12. Adolescents were severely sleep deprived, with mean school-night total sleep times of 6.02, 5.62, and 4.86 hours for 10th-, 11th-, and 12th-graders, respectively. In the higher grades, there was a greater discrepancy between school nights and weekends in terms of bedtime and wake time, and the magnitude of weekend oversleep increased. Older students also reported more daytime sleepiness, more sleep/wake-problem behavior, more depressed mood, and more eveningness preference. The chief reasons students cited for their sleep deprivation differed across grades: Academic demands and entertainment (such as Internet and television) were reported by 5th- and 6th-graders, entertainment and then academic demands by 7th-, 8th-, and 9th-graders, and early school start time and academic demands by 10th-, 11th- and 12th-graders.

CONCLUSIONS

This study clearly demonstrates that Korean adolescents do not get adequate sleep and that they have profound discrepancies in their sleep/wake patterns between school and weekend nights. Compared with previous studies from other countries, Korean students display even greater sleep deprivation and also more irregular sleep/wake patterns. This study also demonstrates that academic demands/stress and early school start time are the most important contributing factors for sleep deprivation among Korean adolescents. These findings stress the need to promote awareness of the magnitude of adolescent sleep deprivation and its detrimental effects in Korean society.