Effect of experimental change in children's sleep duration on television viewing and physical activity.

BACKGROUND: Paediatric observational studies demonstrate associations between sleep, television viewing and potential changes in daytime activity levels. OBJECTIVE(S): To determine whether experimental changes in sleep lead to changes in children's sedentary and physical activities. METHODS: Using a within-subject counterbalanced design, 37 children 8-11 years old completed a 3-week study. Children slept their typical amount during a baseline week and were then randomized to increase or decrease mean time in bed by 1.5 h/night for 1 week; the alternate schedule was completed the final week. Children wore actigraphs on their non-dominant wrist and completed 3-d physical activity recalls each week. RESULTS: Children reported watching more television (p < 0.001) and demonstrated lower daytime actigraph-measured activity counts per epoch (p = 0.03) when sleep was decreased (compared with increased). However, total actigraph-measured activity counts accrued throughout the entire waking period were higher when sleep was decreased (and children were awake for longer) than when it was increased (p < 0.001). CONCLUSION(S): Short sleep during childhood may lead to increased television viewing and decreased mean activity levels. Although additional time awake may help to counteract negative effects of short sleep, increases in reported sedentary activities could contribute to weight gain over time.

Dissipation of sleep pressure is stable across adolescence.

The sleep electroencephalogram (EEG) undergoes many changes during adolescence. We assessed whether sleep homeostasis is altered across adolescent development using two measures: the dissipation of slow-wave activity (SWA, 0.6-4.6Hz) across the night and the rate of build-up of SWA in the first non-rapid eye movement (NREM) sleep episode. Furthermore, we examined the association between homeostatic and circadian measures, by correlating the build-up of SWA in the first non-rapid eye movement (NREM) sleep episode with circadian phase. Finally, we compared the dissipation of SWA in individuals with (PH+) and without (PH-) a parental history of alcohol abuse/dependence. Twenty children (8 PH+) and 25 teens (10 PH+) underwent two consecutive polysomnographic recordings at ages 9/10 and 15/16 years and again 1.5-3 years later. Thirteen young adults (ages 20-23 years; no PH+) were assessed one time. The decay of Process S was modeled for each individual at each assessment using data from both recordings. Four parameters of Process S were derived for EEG derivation C3/A2: time constant of the decay, lower asymptote (LA), the level of S at sleep onset (S(SO)), and S(SO) minus LA. We found no change in these parameters between assessments for the children and teen cohorts. Between-subject analysis of the follow-up assessment for children (ages 11-13 years) and the initial assessment for teens (ages 15/16 years) showed no difference in these parameters, nor did follow-up assessment of teens (ages 17-19 years) compared to the single assessment of young adults (ages 20-23 years). Similarly, we observed no developmental changes in the rate of the build-up of SWA in the first NREM sleep episode for our within- and between-subject analyses, or a correlation between this measure and circadian phase for either cohort. With regard to parental alcohol history, we found no difference in the dissipation of sleep pressure between PH+ and PH- children and teens. These results indicate that the dissipation of sleep pressure does not change across adolescent development, is not correlated with circadian phase, and does not differ between PH+ and PH- children and teens.

Developmental changes in brain connectivity assessed using the sleep EEG.

Adolescence represents a time of significant cortical restructuring. Current theories posit that during this period connections between frequently utilized neural networks are strengthened while underutilized synaptic connections are discarded. The aim of the present study was to examine the developmental evolution of connectivity between brain regions using the sleep EEG. All-night sleep EEG recordings in two longitudinal cohorts (children and teens) followed at 1.5-3 year intervals and one cross-sectional cohort (adults) were analyzed. The children and teen cohorts were 9/10 and 15/16 years at the initial assessment; ages of the adults were 20 to 23 years. Intrahemispheric, interhemispheric, and diagonal coherence was measured between all six possible pairings of two central (C3/A2 and C4/A1) and two occipital (O2/A1 and O1/A2) derivations during slow wave, stage 2, and, REM sleep. Within-subjects analyses were performed for the children and teen cohorts, and a linear regression analysis was performed across every assessment of all cohorts. Within-subject analyses revealed a maturational increase in coherence for both age cohorts, though the frequencies, sleep states, and regions differed between cohorts. Regression analysis across all age cohorts showed an overall linear increase in left and right intrahemispheric coherence for all sleep states across frequencies. Furthermore, coherence between diagonal electrode pairs also increased in a linear manner for stage 2 and REM sleep. No age-related trend was found in interhemispheric coherence. Our results indicate that sleep EEG coherence increases with age and that these increases are confined to specific brain regions. This analysis highlights the utility of the sleep EEG to measure developmental changes in brain maturation.

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.

Effects of acute sleep restriction on behavior, sustained attention, and response inhibition in children.

This study examined the effects of acute sleep restriction on the day-time behavior and performance of healthy children and adolescents. 82 participants (8 to 15 years of age) completed 5 nights of baseline sleep and were randomly assigned to Optimized (10 hr.) or Restricted (4 hr.) sleep for an overnight lab visit. Behavior, performance, and sleepiness were assessed the following day. Sleep restriction was associated with shorter daytime sleep latency, increased subjective sleepiness, and increased sleepy and inattentive behaviors but was not associated with increased hyperactive-impulsive behavior or impaired performance on tests of response inhibition and sustained attention. Results are discussed in terms of current theories regarding effects of inadequate or disturbed sleep among children and adolescents.

Extended nights, sleep loss, and recovery sleep in adolescents.

In summary, this study of sleep in adolescents on an atypical schedule of 18-hour nights showed marked but not unanticipated differences in sleep as function of prior sleep deprivation. Unanticipated was the evidence of "recovery" sleep in adolescents who not only were not sleep deprived, but who had been on a sleep "optimizing" schedule and had been awake for only 10 hours. Extended sleep beginning about 4 hours in advance of entrained sleep onset phase was not associated with a return of SWS, a finding coinciding with predictions from studies in adults. Finally, this study provides an indication that the homeostatic sleep/wake process becomes less robust or sleep responsive during adolescent development, a phenomenon that may influence the delay of sleep common in adolescents.

Developmental features of sleep.

In sum, sleep disorders are common problems for children and adolescents, with estimates indicating that approximately 20% to 25% of the pediatric population experiences some type of sleep disturbance. Furthermore, clinicians should be aware that sleep disturbances may not only exist in isolation, but can be related to psychiatric or medical issues. Although much appears to be known about sleep disorders in the pediatric population, our knowledge of this area is still in its infancy. Additional research is still needed to investigate differences in clinical presentation of specific sleep disturbances among different age groups (i.e., children, adolescents, adults, and elderly), to develop the most appropriate treatments for given populations, and to study the effects of sleep disturbances on functioning. Given the prevalence of these problems in the child and adolescent population and its likely impact on cognitive and behavioral functioning, health professionals need to become increasingly aware of and knowledgeable about sleep and sleep disorders. We all spend about one third of our lives sleeping, or trying to sleep; thus, we should understand as much as we can about it.

Estimating sleep patterns with activity monitoring in children and adolescents: how many nights are necessary for reliable measures?

STUDY OBJECTIVES: This study provides estimates of reliability for aggregated values from 1 to 7 recording nights for five commonly used actigraphic measures of sleep patterns, reliability as a function of night type (weeknight or weekend night), and stability of measures over several months. DESIGN AND SETTING: Data are from three studies that obtained 7 nights of actigraph data (using Mini Motionlogger actigraphs and associated validated algorithms [ASA]) on children and adolescents living at home on self-selected sleep-wake schedules. PARTICIPANTS: Participants were 169 children aged 12-60 months, and 55 adolescents aged 11-16 years. MEASUREMENTS AND RESULTS: Up to 28% of weekly recordings may be unacceptable for analysis in young participants because of illness, technical problems, and participant noncompliance; studies aiming to collect 5 nights of actigraph data should record for at least 1 full week. Reliability estimates for values aggregated over any 5 nights were adequate (> or = .70) for sleep start time, wake minutes, and sleep efficiency. Measures of sleep minutes and sleep period were less reliable and may require 7 or more nights for estimates of stable individual differences. Reliability for 1- or 2-night aggregates were poor for all measures. We found significant and high correlations between summer and fall session measures for all five variables when weekend nights were included. CONCLUSIONS: Five or more nights of usable recordings are required to obtain reliable actigraph measures of sleep for children and adolescents.

Intrinsic circadian period of adolescent humans measured in conditions of forced desynchrony.

Circadian timing was assessed with forced desynchrony (FD) in 10 healthy adolescents (five boys, five girls; mean age 13.7 years). Following 10 days of entrainment to a fixed light-dark (LD) schedule at home, participants were studied under dim light (<20 lux) in the laboratory. A 28-h schedule (FD) was imposed for 12 x 28-h cycles. Saliva was collected at 30- or 60-min intervals throughout; core temperature was measured in constant routines (CR) before and after FD. Intrinsic circadian period was estimated by linear regression using temperature minimum from CRs and dim-light salivary melatonin onsets and offsets from FD. Average intrinsic circadian period for core temperature (n = 7) was 24.30+/-0.20, for melatonin onset was 24.33+/-0.21, and for melatonin offset was 24.35+/-0.21. Intrinsic circadian period in every adolescent was greater than 24 h.

Sleep schedules and daytime functioning in adolescents.

Sleep and waking behaviors change significantly during the adolescent years. The objective of this study was to describe the relation between adolescents' sleep/wake habits, characteristics of students (age, sex, school), and daytime functioning (mood, school performance, and behavior). A Sleep Habits Survey was administered in homeroom classes to 3,120 high school students at 4 public high schools from 3 Rhode Island school districts. Self-reported total sleep times (school and weekend nights) decreased by 40-50 min across ages 13-19, ps < .001. The sleep loss was due to increasingly later bedtimes, whereas rise times were more consistent across ages. Students who described themselves as struggling or failing school (C's, D's/F's) reported that on school nights they obtain about 25 min less sleep and go to bed an average of 40 min later than A and B students, ps < .001. In addition, students with worse grades reported greater weekend delays of sleep schedule than did those with better grades. Furthermore, this study examined a priori defined adequate sleep habit groups versus less than adequate sleep habit groups on their daytime functioning. Students in the short school-night total sleep group (< 6 hr 45 min) and/or large weekend bedtime delay group (> 120 min) reported increased daytime sleepiness, depressive mood, and sleep/wake behavior problems, ps < .05, versus those sleeping longer than 8 hr 15 min with less than 60 min weekend delay. Altogether, most of the adolescents surveyed do not get enough sleep, and their sleep loss interferes with daytime functioning.

Parental report of sleep problems in children with attentional and learning disorders.

This study examined whether parents of children diagnosed with neurodevelopmental disorders (n = 79) report greater sleep-related problems in their offspring than do parents of normal community-based children (n = 86) on a research questionnaire developed to assess sleep and breathing problems, sleepiness, and behavioral problems. Clinical subgroups included: attention deficit/hyperactivity disorder (ADHD) (n = 43), learning disabilities (LD) (n = 11), and combined ADHD/LD (n = 25). Analyses revealed that parents of children with neurodevelopmental disorders report greater problems along all three dimensions than parents of normal control children. Sleep-related difficulties were reported at the same frequency across all three clinical subgroups. No significant difference between clinical and control groups was noted, however, in the reported length of sleep on weeknights. These preliminary findings suggest that sleep-related problems need to be routinely reviewed as part of the clinical evaluation of neurodevelopmental problems, because they may contribute to and/or exacerbate the behavioral manifestation of these disorders.

Adolescent sleep patterns, circadian timing, and sleepiness at a transition to early school days.

STUDY OBJECTIVES: This study examined effects on adolescent sleep patterns, sleepiness, and circadian phase of a school transition requiring an earlier start. DESIGN AND SETTING: Adolescents were evaluated in 9th and 10th grades; school start time in 9th grade was 0825 and in 10th grade was 0720. Assessments at each point included 2 weeks of actigraphy and sleep diaries at home, followed by a 22-hour laboratory evaluation, including evening saliva samples every 30 minutes in dim light for determination of dim-light salivary melatonin onset phase (DLSMO), overnight sleep monitoring, and multiple sleep latency test (MSLT). PARTICIPANTS: Twenty-five females and 15 males, ages 14 to 16.2 were enrolled; 32 completed the study in 9th grade and 26 completed in 10th grade. INTERVENTIONS: Participants kept their own schedules, except that laboratory nights were scheduled based upon school-night sleep patterns. MEASUREMENTS AND RESULTS: According to actigraphy, students woke earlier on school days in 10th than in 9th grade, but they did not go to sleep earlier and they slept less. DLSMO phase was later in 10th grade (mean = 2102) than 9th grade (mean = 2024). Sleep latency on MSLT overall was shorter in 10th (mean = 8.5 minutes) than in 9th (mean = 11.4 minutes), particularly on the first test of the morning at 0830 (5.1 vs 10.9 minutes). Two REM episodes on MSLT occurred in 16% of participants in 10th grade; one REM episode occurred in 48%. When those with REM sleep on one or both morning MSLTs (n = 11) were compared to those without morning REM, significant differences included shorter sleep latency on the first test, less slow wave sleep the night before, and later DLSMO phase in those who had morning REM. CONCLUSIONS: Early start time was associated with significant sleep deprivation and daytime sleepiness. The occurrence of REM sleep on MSLT indicates that clinicians should exercise caution in interpreting MSLT REM sleep in adolescents evaluated on their "usual" schedules. Psychosocial influences and changes in bioregulatory systems controlling sleep may limit teenagers' capacities to make adequate adjustments to an early school schedule.

An approach to studying circadian rhythms of adolescent humans.

The "long nights" protocol was designed to evaluate sleep processes and circadian rhythm parameters in young humans. A total of 19 children (10 boys, ages 11.2 to 14.1 years [mean = 12.7 +/- 1.0], and 9 girls, ages 12.2 to 14.4 years [mean = 13.1 +/- 0.7]) took part in the study. Sleep/wake initially was assessed at home using actigraphy and diary for 1 week on each child's self-selected schedule followed by an 8-night fixed light-dark (LD) condition, while sleeping from 22:00 to 08:00 h and wearing an eye mask to exclude as much light as possible. Phase measurements included 4-night mean actigraphically estimated sleep onset and offset as well as 1-night dim light salivary melatonin onset (DLSMO) phase at the end of each condition. Subjects then lived in the laboratory for 6 consecutive cycles: Day 1 LD = 14:10 h, lights out 22:00 to 08:00 h; Days 2-4 LD = 6:18 h, lights out 18:00 to 12:00 h; Days 5-6 = constant routine in continuous dim light (about 20 lux); Night 6 = 14 h recovery sleep. Phase markers (sleep onset, sleep offset, DLSMO) were significantly less dispersed after the fixed LD as compared to the self-selected condition, indicating efficacy of the LD protocol. Phase markers were correlated at the self-selected assessment (sleep onset vs. sleep offset r = .72; DLSMO vs. sleep onset r = .82; DLSMO vs. sleep offset r = .76) but not on the fixed schedule, probably due to restricted range. The constant routine provided additional phase markers, melatonin offset and midphase. Offset phase of melatonin secretion was significantly correlated with age (r = .62) and Tanner stage (r = .62). In conclusion, these preliminary data indicate a relationship between adolescent development and circadian phase. Thus, the long nights protocol is a feasible way in which to assess circadian parameters in young humans as well as to examine intrinsic sleep processes.

Effects of menopause and nasal occlusion on breathing during sleep.

Prevalence of sleep-disordered breathing (SDB) is reported to increase in menopausal women. We examined response to a nocturnal respiratory challenge (nasal occlusion) during overnight polysomnography in 31 women (45 to 55 yr). Thirteen were premenopausal, four perimenopausal, and 14 postmenopausal by history and hormonal assay. Nasal occlusion increased the apnea hypopnea index (AHI) (occlusion mean = 6.6 +/- 8.0 versus baseline mean = 1.6 +/- 2.6, p < 0.01) and arousal index (occlusion mean = 35.1 +/- 20.1 versus baseline mean = 20.7 +/- 11.6, p < 0.001), but did not change the oxygen saturation nadir in those with respiratory events (occlusion mean = 91.8 +/- 4.2 versus baseline mean = 92.0 +/- 11.6). Menopausal groups did not differ on AHI, arousal index, or oxygen saturation nadir in either condition. Key variables were compared between occlusion responders (n = 11) and nonresponders (n = 20). Responders and nonresponders were not distinguished by age, menopausal status, nor several cephalometric or anthropometric variables. Body mass index (31.1 +/- 8.5 versus 24.3 +/- 3.4, p < 0.003), neck circumference (34.0 +/- 2.5 versus 32.5 +/- 1.7 cm, p < 0.05), and mandibular-hyoid distance (18.5 +/- 3.8 versus 14.5 +/- 5.7 mm, p < 0.05) were greater in responders. These findings suggest hormonal factors may be less important than weight and facial morphology in midlife development of SDB in women.

Environmental noise as a cause of sleep disruption in an intermediate respiratory care unit.

Our laboratory previously reported continuously monitored peak sound levels in several areas at Rhode Island Hospital. The number of sound peaks greater than 80 A-weighted decibels (dBA) was found to be high in the intensive and intermediate respiratory care unit (IRCU) areas, even at night. Environmental noise of this magnitude is potentially sleep-disruptive. Therefore, we hypothesized that nocturnal peak sound levels of > or = 80 dBA would be associated with an increase in EEG arousals from sleep in patients in the IRCU. Six patients underwent sleep monitoring while environmental peak sound levels were continuously recorded. Each 8-hour period (2200 to 0600 hours) was broken down into 30-minute segments. If there were 10 minutes or more of wakefulness in a segment, that segment was dropped from further analysis. Of the remaining 61 segments, there was a very strong correlation (r = 0.57, p = 0.0001) between the number of sound peaks of > or = 80 dBA and arousals from sleep. These 61 periods were then classified as quiet, moderately loud, and very loud based on the number of sound peaks (< or = 5, 6-15, and > 15, respectively). Analysis of variance revealed a significant difference between the number of arousals (p = 0.001) in quiet periods and that in very loud periods. We conclude that environmental noise may be an important cause of sleep disruption in the IRCU.

Relationship between sleepiness and general health status.

One commonly used instrument for evaluating general health and functional status is the medical outcomes survey short form 36 (MOS). Scores obtained from this instrument are known to vary with chronic diseases and depression. However, the degree to which these health dimensions may be influenced by sleep quality or sleepiness is not well understood. A cross-sectional study was performed on the association between general health status, as determined by the MOS, with sleepiness, assessed using a standardized questionnaire [the Epworth sleepiness scale (ESS)] and the multiple sleep latency test (MSLT). One hundred twenty-nine subjects (68 women), aged 25-65 years, without severe chronic medical or psychiatric illnesses, underwent an overnight sleep study, followed by an MSLT (consisting of a series of four attempts at napping at 2-hour intervals), and completed the MOS and the ESS. The mean MSLT score was 11 +/- 2 minutes, (range 2-20) and the mean ESS score was 10 +/- 5 (range 0-24). Scores for the MOS dimensions "general health perceptions", "energy/fatigue", and "role limitations due to emotional problems" were correlated significantly with ESS scores (r = -0.30, -0.41, and -0.30, respectively; p values were all < 0.001). The MSLT was also significantly correlated with "energy/fatigue" (r = -0.19; p < 0.05). After considering the effects of chronic illness and/or body mass index in a multiple hierarchical regression analysis, sleepiness, as assessed by the ESS score, explained 8% of the variance in general health perceptions, 17% of the variance in energy/fatigue, 6% of the variance in the summary measure of well-being, and 3% of the variance in the summary measure of functional status. The variation of MOS scores with sleepiness, unrelated to age or chronic disease, suggests that measures of general health status may be broadly influenced by sleepiness and sleep quality. These data suggest that 1) sleepiness has an important impact on general health and functional status, specifically influencing self-perceptions regarding energy/fatigue; 2) a more specific assessment of sleepiness in general health evaluations may help explain some of the observed variability in these measures across subjects; and 3) general health measures may be useful in the evaluations of patients with sleep disorders.

The effects of regularizing sleep-wake schedules on daytime sleepiness.

The present study evaluated the differential effects of two manipulations of sleep-wake schedules on daily subjective ratings of daytime sleepiness of college undergraduate students. Two experimental conditions were compared: a sleep only group and a regularity group. Subjects in both conditions were given a lower limit for total sleep time (7.5 hours). Subjects in the regularity group received an additional instruction to keep a regular sleep schedule. The study was longitudinal and prospective. Following a baseline period (12 days), the experimental conditions were introduced. The experimental phase lasted 4 weeks and overall compliance was good. A follow-up phase (1 week) began 5 weeks past termination of the experimental phase. The findings indicated that when nocturnal sleep is not deprived, regularization of sleep-wake schedules is associated with reduced reported sleepiness. Subjects in the regular schedule condition reported greater and longer lasting improvements in alertness compared with subjects in the sleep only condition and reported improved sleep efficiency.

Sleep, breathing, and cephalometrics in older children and young adults. Part I -- Normative values.

STUDY OBJECTIVES: Aims were (1) to provide normative values for sleep and sleep-related breathing variables and physical features (cephalometrics, body mass index [BMI], and tonsillar size) in older children/adolescents and young adults, (2) to describe sex and age group differences, and (3) to evaluate relationships between physical features and sleep-related breathing variables. DESIGN: Standard polysomnographic variables describing sleep and breathing were measured during a single night. Cephalometric measures were obtained from a standing lateral skull radiograph. SUBJECTS: Normal, healthy boys (n=23; mean age=13.3+/-2.1 years), girls (n=22; mean age =13.8+/-1.8 years), men (n=23; mean age=22.2+/-1.5 years), and women (n=24; mean age=22.4+/-1.8 years) with BMI less than 27 were evaluated. RESULTS: Sleep variables showed age group and sex differences consistent with published norms. Slow-wave sleep and rapid eye movement (REM) latency declined with age; transient arousals increased with age. Sleep-related breathing variables showed few changes related to age group or sex; small but statistically significant sex differences were found for arterial oxygen saturation nadir (lower in male subjects) and respiration disturbance index in non-REM sleep (greater in male subjects). Differences in cephalometric measures largely reflected normal growth and expected sex differences. No significant relationships between sleep-related breathing variables and physical findings were observed. CONCLUSIONS: These data provide well-controlled normative values for sleep, breathing, and cephalometrics in a group of normal older children, adolescents, and young adults. The data provide useful reference points for patients of these ages in whom sleep apnea is suspected, particularly since such clinical studies are normally based on first-night polysomnography. Furthermore, these values represent developmentally appropriate grouping of the data.

Sleep, breathing, and cephalometrics in older children and young adults. Part II -- Response to nasal occlusion.

STUDY OBJECTIVES: We postulated that nasal occlusion would provide a challenge enabling us to assess factors predisposing development of sleep apnea in older children/adolescents and young adults. Factors of interest included sex, age, body mass index (BMI), tonsillar hypertrophy, and cephalometric measurements. DESIGN: Sleep and breathing variables were examined and compared for four groups of subjects between one baseline night and one night of nasal occlusion in a sleep research laboratory. SUBJECTS: Healthy, normal boys (n=23, mean age=13.3+/-2.1 years), girls (n=22, mean age=13.8+/-1.8 years), men (n=23, mean age=22.2+/-1.5 years), and women (n=24, mean age=22.4+/-1.8 years) were studied. MEASUREMENTS AND RESULTS: The following sleep and sleep-related breathing measures showed significant increases in all four groups from baseline to occlusion: percentage of stage 1, number of transient arousals, transient arousal index, apnea index, respiratory disturbance index (RDI), and mean apnea length. No significant relationships were found between occlusion-night RDI and tonsillar size, cephalometric variables, or BMI, either singly or in combination. CONCLUSIONS: Subjects' responses to nasal occlusion varied: most demonstrated a minimal and clinically insignificant increase in RDI; few showed a marked increase in RDI. Significant increases of sleep fragmentation -- even in the absence of frankly disturbed breathing -- indicate that nasal occlusion may secondarily affect waking function if prolonged over a series of nights.