Ontogenetic variations in auditory arousal threshold during sleep

Awake or Sleeping? Maybe Both… A Review of Sleep-Related Dissociative States

Recent studies have begun to understand sleep not only as a whole-brain process but also as a complex local phenomenon controlled by specific neurotransmitters that act in different neural networks, which is called "local sleep". Moreover, the basic states of human consciousness-wakefulness, sleep onset (N1), light sleep (N2), deep sleep (N3), and rapid eye movement (REM) sleep-can concurrently appear, which may result in different sleep-related dissociative states. In this article, we classify these sleep-related dissociative states into physiological, pathological, and altered states of consciousness. Physiological states are daydreaming, lucid dreaming, and false awakenings. Pathological states include sleep paralysis, sleepwalking, and REM sleep behavior disorder. Altered states are hypnosis, anesthesia, and psychedelics. We review the neurophysiology and phenomenology of these sleep-related dissociative states of consciousness and update them with recent studies. We conclude that these sleep-related dissociative states have a significant basic and clinical impact since their study contributes to the understanding of consciousness and the proper treatment of neuropsychiatric diseases.

Pre-Sleep Cognitive Arousal Is Unrelated to Sleep Misperception in Healthy Sleepers When Unexpected Sounds Are Played during Non-Rapid Eye Movement Sleep: A Polysomnography Study

Background: It is well-established that environmental noise can disrupt sleep, and cause a mismatch between subjective and objective sleep, which is known as “sleep misperception”. Naturalistic studies indicate that pre-sleep cognitive arousal and sleep misperception are associated in the context of noise. However, it is not known if this is the case when ecologically valid noises are specifically played during non-rapid eye movement (NREM) sleep, which is susceptible to noise-related disruption. The present study evaluated if pre-sleep cognitive arousal was associated with sleep misperception in healthy normal sleepers, when unexpected ecologically valid common nocturnal noises were played during NREM sleep. Methods: Eighteen healthy sleepers (M_age = 23.37 years, SD_age = 3.21 years) participated. Sleep was measured objectively on three consecutive nights using polysomnography, in a sleep laboratory environment, and subjectively, through participant estimates of total sleep time (TST). Night 1 was a baseline night where no noises were played. On Night 2, noises, which were chosen to be representative of habitual nocturnal noises heard in home environments, were played to participants via in-ear headphones after 5 min of objective sleep. Results: Unexpectedly, habitual pre-sleep cognitive arousal was not associated with subjective–objective TST discrepancy on Night 2. Conclusions: These results suggest that in healthy sleepers, when ecologically valid noises are played unexpectedly during NREM sleep in an unfamiliar sleep laboratory environment the subjective experience of sleep is not associated with pre-sleep cognitive arousal, or negatively impacted by noise exposure.

Age-Dependent Responsiveness to Smoke Alarm Signals Among Children

OBJECTIVES

Although it has been established that smoke alarms have more difficulty awakening children from sleep than adults, no attempt has been previously made to characterize how smoke alarm responsiveness changes with age during childhood. The objective of this study is to evaluate the age-dependent responsiveness to various smoke alarm signals among children 5 to 12 years old.

METHODS

The effect of age on children's response to 4 types of smoke alarms (human voice, hybrid voice-tone, low-frequency tone, and high-frequency tone) was evaluated using combined data from 3 previous studies.

RESULTS

There were 540 subjects (median age 9 years; 51.7% male). The proportion of children who awakened demonstrated a statistically significant (P < .001) increase of 3.1% to 7.6% for each additional year of age between 5 and 12 years old for the 4 alarm types. Similarly, child age showed a statistically significant (P < .001) effect on the proportion who escaped for each of the 4 alarm types. The proportion of subjects who awakened or escaped did not differ significantly by sex for any of the alarm types. Median time-to-awaken and median time-to-escape decreased with increase in child age for all alarm types.

CONCLUSIONS

This study demonstrates the substantial influence of child age on the effectiveness of audible smoke alarms during childhood. Among 12-year-olds, only 56.3% escaped within 1 minute (and 67.6% within 2 minutes) to a high-frequency tone. However, a hybrid voice-low-frequency tone alarm is >96% effective at awakening and prompting escape within 1 minute among children 9 years and older.

Pre-Sleep Cognitive Arousal Is Negatively Associated with Sleep Misperception in Healthy Sleepers during Habitual Environmental Noise Exposure: An Actigraphy Study

Specific noises (e.g., traffic or wind turbines) can disrupt sleep and potentially cause a mismatch between subjective sleep and objective sleep (i.e., “sleep misperception”). Some individuals are likely to be more vulnerable than others to noise-related sleep disturbances, potentially as a result of increased pre-sleep cognitive arousal. The aim of the present study was to examine the relationships between pre-sleep cognitive arousal and sleep misperception. Sixteen healthy sleepers participated in this naturalistic, observational study. Three nights of sleep were measured using actigraphy, and each 15-s epoch was classified as sleep or wake. Bedside noise was recorded, and each 15-s segment was classified as containing noise or no noise and matched to actigraphy. Participants completed measures of habitual pre-sleep cognitive and somatic arousal and noise sensitivity. Pre-sleep cognitive and somatic arousal levels were negatively associated with subjective−objective total sleep time discrepancy (p < 0.01). There was an association between sleep/wake and noise presence/absence in the first and last 90 min of sleep (p < 0.001). These results indicate that higher levels of habitual pre-sleep arousal are associated with a greater degree of sleep misperception, and even in healthy sleepers, objective sleep is vulnerable to habitual bedside noise.

Self-reported developmental changes in the frequency and characteristics of somnambulistic and sleep terror episodes in chronic sleepwalkers

BACKGROUND

Far from being benign, somnambulistic episodes can be frequent and/or severe and potentially injurious. Episodes may also be accompanied by sleep mentation with variable degrees of retrograde amnesia. The present study investigated how somnambulistic episodes unfold from childhood through adulthood, a topic that remains understudied.

METHODS

Adult sleepwalkers with a diagnosis of primary somnambulism and a childhood onset of the disorder (n = 113) were assessed for changes in frequency of their episodes, recall of episode-related sleep mentation and aggressive episodes during childhood, adolescence and adulthood. In addition, sleepwalkers (n = 52) with childhood-onset of sleep terrors were assessed for developmental changes in sleep terror frequency.

RESULTS

Results indicate that the frequency of somnambulistic episodes remains unchanged during childhood and adolescence before increasing during adulthood. An opposite trend was observed for sleep terrors. The frequency of aggressive somnambulistic episodes and of sleep mentation associated with somnambulism increased from childhood to adolescence and into adulthood. By contrast, the recall of sleep mentation associated with sleep terrors did not change over time. Additionally, a higher frequency of aggressive somnambulistic episodes predicted a higher frequency of sleep mentation associated with somnambulism. These patterns were similar across men and women.

CONCLUSION

Our study demonstrates that in chronic sleepwalkers, sleep mentation associated with somnambulistic episodes increases with age while episodes worsen in frequency and severity from childhood to adulthood. These findings add to the limited literature in the field and provide valuable insights into how key clinical characteristics of somnambulism evolve across the lifespan.

Observations of Acoustic Interruptions Versus Ambient Sound Levels With Perceived Sleep Quality During Critical Illness

ICUs are loud and there is an association between ambient sound and worsened sleep quality. In contrast to ambient sound, short acoustic interruptions or sound spikes—for example, brief alarm tones—cause arousal from sleep in healthy patients, but remain understudied in critically ill patients, despite the observed frequency of ICU alarms. We collected greater than 2.3 million values of ambient sound (every second) among 14 patients in the ICU over a median of two nights (interquartile range, 1–2) each. We identified brief acoustic interruptions/sound spikes—increases of greater than or equal to 20 dB above ambient—over 1 second. Patients experienced a median of five interruptions greater than or equal to 20 dB (interquartile range, 2–12) per night. Each interruption was associated with a 1-point decrease in patient reported quality of sleep, as assessed by the Richards Campbell Sleep Questionnaire. Our observations suggest a possible relationship between acoustic interruptions and worsened perceived sleep.

Comparison of the effectiveness of female voice, male voice, and hybrid voice-tone smoke alarms for sleeping children

BACKGROUND

To test whether children awaken from slow wave sleep and perform an escape procedure better in response to a smoke alarm that uses a male voice, female voice, combination of a low-frequency tone plus a female voice (hybrid alarm), or high-frequency tone.

METHODS

Using a randomized, non-blinded, repeated-measures design, 188 children aged 5-12 years were exposed during stage 4 slow wave sleep to four smoke alarms.

RESULTS

Among study subjects, 84.6%, 87.2%, 88.8%, and 56.4% awakened and 84.0%, 86.7%, 88.8%, and 55.3% successfully performed the escape procedure within 5 min of alarm onset in response to the male voice, female voice, hybrid, and high-frequency tone alarms, respectively, while the median time-to-escape was 12.0, 12.0, 13.0, and 96.5 s for these four alarms, respectively. All pairwise comparisons between the high-frequency tone alarm and each of the other three alarms were statistically significant for the proportions of subjects who awakened or escaped and for time-to-awaken and time-to-escape. There were no significant differences in these outcome measures between the latter three alarms.

CONCLUSIONS

Use of the male or female voice or hybrid alarms in children's sleep areas may reduce residential fire-related injuries and deaths among children old enough to perform self-rescue.

IMPACT

The male voice, female voice, and hybrid alarms were each significantly more effective than a high-frequency tone alarm in awakening children aged 5-12 years from slow wave sleep and prompting their performance of an escape procedure. There were no significant differences in the effectiveness of the male voice, female voice, and hybrid alarms when compared with each other. Use of these alarms in children's sleep areas may reduce residential fire-related injuries and deaths among children old enough to perform self-rescue.

Optimizing smoke alarm signals: Testing the effectiveness of children's smoke alarms for sleeping adults

Background

Being asleep is an important risk factor for death during a residential fire; however, the high-frequency tone smoke alarms in many homes will not adequately awaken children who are old enough to self-rescue. In a series of previous studies, we identified smoke alarm signals that effectively awaken children 5–12 years old and prompt their escape. Because it is impractical to have separate alarms for children and adults in a household, the purpose of this study is to test whether alarms that are effective in awakening children and prompting their escape are also effective among adults.

Methods

Using a randomized, non-blinded, repeated measures design, 150 adults 20–49 years old were exposed during stage 4 sleep to four different smoke alarms. Statistical tests included the Kaplan-Meier estimator, generalized Wilcoxon test, and hazard ratios with Wald’s 95% confidence intervals.

Results

The median age of study subjects was 30.0 years and 67.3% were female. Almost all (n = 149) subjects awakened and performed the escape procedure to all four alarms; one individual did not awaken or escape to the high-frequency tone alarm. The median time-to-awaken was 2.0 s for the high-frequency tone alarm and 1.0 s for the other three alarms. The median time-to-escape for the high-frequency tone alarm was 12.0 s, compared with 10.0 s for the low-frequency tone alarm and 9.0 s each for the female and male voice alarms. All pairwise comparisons between the high-frequency tone alarm and each of the other three alarms were statistically significant for the probability functions for time-to-awaken and time-to-escape. There were no significant differences in these outcome measures between the latter three alarms, except for female voice versus low-frequency tone alarms for time-to-escape.

Conclusions

All alarms performed well, demonstrating that smoke alarms developed for the unique developmental requirements of sleeping children are also effective among sleeping adults. Compared with a high-frequency tone alarm, use of these alarms may reduce residential fire-related injuries and deaths among children, while also successfully alerting adult members of the household.

Obstructive sleep apnea and insulin resistance in children with obesity

STUDY OBJECTIVES

Because existing data investigating obstructive sleep apnea (OSA) and insulin resistance (IR) are inconsistent, we examine OSA and IR in a pediatric obesity clinic.

METHODS

Children (2-18 years) in the obesity clinic (2013-2017) undergoing polysomnography (PSG), anthropometric measurements, and fasting laboratory tests were included. Linear regression assessed OSA defined by the obstructive apnea-hypopnea index (oAHI) with the homeostatic model assessment of insulin resistance (HOMA-IR). Secondary aims assessed oxygen desaturation index (ODI) and age interactions with HOMA-IR. Logistic regression models and receiver operating characteristic analysis were performed to investigate optimal oAHI and ODI cutoffs relative to HOMA-IR ≥ 3.

RESULTS

Eighty children were included (mean age, 11.4 ± 4.0 years; 56% female; 46% Caucasian; median body mass index [BMI], 34.6 kg/m² [interquartile ratio, 29.9-40.1], median BMI z-score, 2.5 [interquartile ratio, 2.3-2.8); 46% with oAHI ≥ 5 events/h. HOMA-IR was higher in the OSA group (oAHI ≥ 5 events/h): 5 vs 3.8 (P = .034). After adjustment for sex, race, and BMI z-score, oAHI ≥ 5 events/h retained significance with HOMA-IR (P = .041). HOMA-IR increased in older children (age ≥ 12 years) when adjusting for waist circumference z-score and waist-height ratio (statistical interaction, P = .020 and .034, respectively). Receiver operating characteristic showed optimal cut points of oAHI and ODI for predicting significant IR 4.9 (area under the curve, 0.70; 95% confidence interval, 0.57-0.83; sensitivity, 0.76; specificity, 0.66) and 4.6 (area under the curve, 0.68; 95% confidence interval, 0.55-0.80; sensitivity, 0.70; specificity, 0.67), respectively.

CONCLUSIONS

In a clinic-based pediatric cohort with obesity, OSA is associated with increased IR even after adjusting for confounders including obesity defined by the BMI z-score. Age ≥ 12 years was associated with AHI relative to IR after adjustment for waist circumference z-score and waist-height ratio. Significant IR could be discriminated by oAHI ≥ 4.9 with moderate sensitivity/specificity. Future studies are needed to verify these findings.

Comparing two measures of sleep depth/intensity

Study Objectives

To compare delta spectral power (delta) and odds ratio product (ORP) as measures of sleep depth during sleep restriction with placebo or a drug that increases delta.

Methods

This is a secondary analysis of data from a study of 41 healthy participants randomized to receive placebo or gaboxadol 15 mg during sleep restriction. Participants underwent in-laboratory sleep studies on two baseline, four sleep restriction (5-h), and two recovery nights. Relation between delta or ORP and sleep depth was operationally defined as the degree of association of each metric to the probability of arousal or awakening occurring during the next 30 s (arousability).

Results

ORP values in wake, N1, N2, N3, and REM were significantly different. Delta differed between both N2 and N3 and other sleep stages but not between wake and N1 or N1 and REM. Epoch-by-epoch and individual correlations between ORP and delta power were modest or insignificant. The relation between ORP and arousability was linear across the entire ORP range. Delta also changed with arousability but only when delta values were less than 300 μV2. Receiver-operating-characteristic analysis found the ability to predict imminent arousal to be significantly greater with ORP than with log delta power for all experimental conditions. Changes in ORP, but not log delta, across the night correlated with next-day physiologic sleep tendency.

Conclusions

Compared to delta power, ORP is more discriminating among sleep stages, more sensitive to sleep restriction, and more closely associated with arousability. This evidence supports ORP as a measure of sleep depth/intensity.

Do Sleeping Children Respond Better to a Smoke Alarm That Uses Their Mother's Voice?

OBJECTIVE

Being asleep at the time of a residential fire increases fire-related fatality risk. This study tested whether children awaken from slow wave sleep and perform an escape procedure better to a voice smoke alarm that uses their mother's voice compared with a female stranger's voice or a low-frequency tone alarm.

METHODS

Using a randomized, nonblinded, repeated measures design, 176 children 5 to 12 years old were exposed during stage 4 slow wave sleep to 4 smoke alarm signals: 1) the voice of the child's mother, 2) the voice of a female stranger, 3) low-frequency 500 Hz square wave tone, and 4) conventional residential high-frequency tone. The alarms were assessed regarding their ability to awaken the children and prompt their performance of an escape procedure.

RESULTS

Among the 176 subjects, 78.4%, 83.0%, 88.1%, and 49.4% awakened and 78.4%, 81.3%, 85.8%, and 48.3% successfully performed the escape procedure within 5 minutes of alarm onset in response to the mother's voice, stranger's voice, low-frequency tone, and high-frequency tone alarms, respectively; while the median time-to-escape was 23.0, 24.0, 41.5, and >300 seconds for these 4 alarms, respectively.

CONCLUSIONS

The 2 voice alarms and low-frequency tone alarm significantly outperformed the high-frequency tone alarm, with the low-frequency tone alarm and female stranger's voice alarm performing best. Compared with the voice of a female stranger, personalizing the alarm message with the voice of the child's mother did not increase alarm effectiveness. These findings provide important information for development of an effective and practical smoke alarm for children.

Locus coeruleus norepinephrine activity mediates sensory-evoked awakenings from sleep

A defining feature of sleep is reduced responsiveness to external stimuli, but the mechanisms mediating sensory-evoked arousal remain unclear. We hypothesized that reduced locus coeruleus (LC) norepinephrine (NE) activity during sleep mediates unresponsiveness, and its action promotes sensory-evoked awakenings. We tested this using electrophysiological, behavioral, pharmacological, and optogenetic techniques alongside auditory stimulation in freely behaving rats. We found that systemic reduction in NE signaling lowered probability of sound-evoked awakenings (SEAs). The level of tonic LC activity during sleep anticipated SEAs. Optogenetic LC activation promoted arousal as evident in sleep-wake transitions, EEG desynchronization, and pupil dilation. Minimal LC excitation before sound presentation increased SEA probability. Optogenetic LC silencing using a soma-targeted anion-conducting channelrhodopsin (stGtACR2) suppressed LC spiking and constricted pupils. Brief periods of LC opto-silencing reduced the probability of SEAs. Thus, LC-NE activity determines the likelihood of sensory-evoked awakenings, and its reduction during sleep constitutes a key factor mediating behavioral unresponsiveness.

Effectiveness of a Voice Smoke Alarm Using the Child's Name for Sleeping Children: A Randomized Trial

OBJECTIVES

To test maternal voice alarm effectiveness under residential conditions and determine whether personalizing the maternal voice alarm message with the child's first name improves effectiveness.

STUDY DESIGN

Using a randomized, nonblinded, repeated measures design, we compared 3 maternal voice smoke alarms with respect to their ability to awaken 176 children 5-12 years old from stage 4 slow-wave sleep and prompt their performance of an escape procedure. A conventional residential high-frequency tone smoke alarm was used as a comparative reference. Children's sleep stage was monitored in a residence-like research setting.

RESULTS

Maternal voice alarms awakened 86%-91% of children and prompted 84%-86% to escape compared with 53% awakened and 51% escaped for the tone alarm. A sleeping child was 2.9-3.4 times more likely to be awakened by each of the 3 voice alarms than the tone alarm. The median time to awaken was 156 seconds for the tone alarm and 2 seconds for each voice alarm. The proportions of children who awakened and escaped differed significantly between the tone alarm and each voice alarm, but no significant differences were found between each pair of the voice alarms, regardless of whether the child's first name was included in the alarm message.

CONCLUSIONS

The maternal voice alarms significantly outperformed the tone alarm under residential conditions. Personalizing the alarm message with the child's first name did not increase alarm effectiveness. These findings have important implications for development of an effective and practical smoke alarm for children.

TRIAL REGISTRATION

ClinicalTrials.gov: NCT01169155.

The characteristics and clinical significance of REM<10% in children with sleep-disordered breathing

OBJECTIVE

Fractional time in REM sleep <20% ('little REM sleep') is indicative of more severe sleep-disordered breathing (SDB) in adults. We examined if other REM% is predictive of more severe SDB in children.

METHODS

In this retrospective study of 616 pediatric SDB patients, age, sex ratio, BMI, sleep efficiency, awakening frequency, sleep latency, apnea-hypopnea index (AHI), obstructive apnea index (OAI), and lowest oxygen pulse saturation (LSpO₂) were compared among groups stratified according to REM%: REM≥20%, REM<20%, 15% ≤ REM<20%, 10% ≤ REM<15%, and REM<10%. Correlations with AHI, OAI, LSpO₂, sleep efficiency, and awakening frequency were examined in REM<20% and REM<10% groups. Associations of these parameters with REM<10% were examined by single- and multifactor regression.

RESULTS

Pediatric SDB patients with little REM sleep demonstrated poorer sleep quality than patients with REM≥20%, while patients with REM<10% also exhibited more severe SDB. Specifically, the REM<20% group exhibited higher number of awakenings and lower sleep efficiency than the REM≥20% group (both P ≤ 0.001), as did each REM%<20% subgroup (lower sleep efficiency: all P < 0.05; higher awakening frequency: all P < 0.001). Moreover, compared to the REM≥20% group, the REM<10% also exhibited higher AHI (P = 0.025) and lower LSpO₂ (P = 0.019). In the REM<10% group, individual REM% was negatively correlated with AHI (r = -0.216, P = 0.031) and positively with LSpO₂ (r = 0.2, P = 0.046). Multifactor logistic regression correcting for age and BMI identified AHI as an independent predictor of REM<10% (P = 0.012, OR = 1.016, 95% CI [1.004,1.029]).

CONCLUSION

REM% <10% is associated with poor sleep quality and SDB severity in children, suggesting that this threshold should define "little REM sleep" in pediatric patients.

Sleep structure and awakening threshold in delayed sleep-wake phase disorder patients compared to healthy sleepers

STUDY OBJECTIVES

Difficult early morning awakening is a primary symptom of delayed sleep-wake phase disorder (DSWPD), however, it remains poorly investigated. Our main objective was to quantify the awakening threshold in DSWPD-patients and healthy controls as well as investigate a possible relationship with sleep stages. A secondary objective was to compare habitual sleep measured by polysomnography and actigraphy between patients and controls.

METHODS

Twenty DSWPD patients and 16 controls had two polysomnographic recordings at a sleep laboratory. Participants followed their habitual sleep-wake schedule on the first night and a forced sleep-wake schedule (00:00-07:00 h) on the second night. We used a custom-made alarm clock was for the forced-night awakening, starting at 72 dB sound intensity which increased up to 104 dB.

RESULTS

Mean awakening threshold in dB was higher in patients compared to controls; 75.5 vs. 72.6, p = 0.01, and the difference could not be explained statistically by sleep-time. Patients who were in REM sleep upon attempted awakening had a higher awakening threshold compared to patients who were in NREM sleep; 80.0 vs 74.7, F = 6.4, p = 0.02. Patients had increased sleep onset latency both at home with actigraphy and by PSG during the first laboratory night (20.6 vs 12.1 min, p = 0.004), however no further differences between the groups were observed regarding sleep structure.

CONCLUSIONS

A high early-morning forced awakening threshold in DSWPD was related to REM sleep. Sleep onset problems, even with habitual bedtimes, may also be an integral feature of DSWPD.

Obstructive Sleep Apnoea: Children are not little Adults

During a child's development, several important developmental physiological sleep processes occur, and, occasionally, pathological disorders occur, which results in differences between obstructive sleep apnoea (OSA) in adults and children. There are major differences in sleep and respiratory physiology as well as OSA symptoms and treatment options between children and adults. Many practitioners do not realize these differences, which results in delays in the diagnosis and treatment of OSA in children. The treatment options for OSA in children are markedly different compared with adults, effective in most children. The use of positive airway pressure (PAP) therapy delivered through continuous or bi-level positive airway pressure modes is successful in children and even in infants; however, there are several challenges facing parents and practitioners to achieve good compliance. The early recognition and treatment of paediatric OSA are essential to prevent deleterious consequences. This article discusses the major differences between paediatric and adult OSA and demonstrates why children are not little adults.

Stressful Events in Early Childhood and Developmental Trajectories of Bedwetting at School Age

Objective To examine whether early stressful events are associated with developmental trajectories of bedwetting. Methods This is a prospective cohort study comprising 8,761 participants from the Avon Longitudinal Study of Parents and Children. Stressful events were measured using a maternal questionnaire completed at 3 time points before their child was 4 years old. The association between stressful events and trajectories of bedwetting from 4 to 9 years was examined using multinomial regression. Results The association with stressful events was strongest for the frequent persistent bedwetting trajectory (wetting at least twice a week up to age 9). A 1 standard deviation increase in the stressful events score was associated with a 29% (13–47%) increase in the odds of experiencing frequent persistent bedwetting compared with normal attainment of nighttime bladder control. Conclusions Clinicians and parents should be aware that continence is a developmental outcome that is associated with high levels of stress in the family.

Reactivity and sleep in infants: a longitudinal objective assessment

Sleep patterns and temperament in the first year of life are closely related. However, research utilizing objective, rather than subjective measurements of sleep and temperament is scarce and results are inconsistent. In addition, a relative lack of longitudinal data prevents inference of causality between the two constructs. In this study, infant sleep was objectively assessed among 95 infants at 3, 6, and 12 months-of-age with an actigraph in the home setting. Reactivity to sound, light, and touch, a specific aspect of temperament, was behaviorally assessed at 3 and 6 months, both during sleep (at home) and during waking (at the laboratory). Expected maturational trends were recorded in sleep, with a temporal increase in sleep efficiency and percent of motionless sleep. Quadratic (i.e., inverse U shape) relations were found, especially among girls, when predicting change in sleep by reactivity thresholds, suggesting that both hyposensitive and hypersensitive infants are at risk for poor sleep quality. These are the first research findings suggesting that low reactivity in infancy might be associated with compromised sleep quality. The observed nonlinear effects may account for null or inconsistent results in previous studies that explored only linear associations between temperament and sleep. Future studies should address both extremes of the temperament continuum when exploring relations with sleep patterns.

Sleep spindle and slow wave frequency reflect motor skill performance in primary school-age children

BACKGROUND AND AIM

The role of sleep in the enhancement of motor skills has been studied extensively in adults. We aimed to determine involvement of sleep and characteristics of spindles and slow waves in a motor skill in children.

HYPOTHESIS

We hypothesized sleep-dependence of skill enhancement and an association of interindividual differences in skill and sleep characteristics.

METHODS

30 children (19 females, 10.7 ± 0.8 years of age; mean ± SD) performed finger sequence tapping tasks in a repeated-measures design spanning 4 days including 1 polysomnography (PSG) night. Initial and delayed performance were assessed over 12 h of wake; 12 h with sleep; and 24 h with wake and sleep. For the 12 h with sleep, children were assigned to one of three conditions: modulation of slow waves and spindles was attempted using acoustic perturbation, and compared to yoked and no-sound control conditions.

ANALYSES

Mixed effect regression models evaluated the association of sleep, its macrostructure and spindles and slow wave parameters with initial and delayed speed and accuracy.

RESULTS AND CONCLUSIONS

Children enhance their accuracy only over an interval with sleep. Unlike previously reported in adults, children enhance their speed independent of sleep, a capacity that may to be lost in adulthood. Individual differences in the dominant frequency of spindles and slow waves were predictive for performance: children performed better if they had less slow spindles, more fast spindles and faster slow waves. On the other hand, overnight enhancement of accuracy was most pronounced in children with more slow spindles and slower slow waves, i.e., the ones with an initial lower performance. Associations of spindle and slow wave characteristics with initial performance may confound interpretation of their involvement in overnight enhancement. Slower frequencies of characteristic sleep events may mark slower learning and immaturity of networks involved in motor skills.

Observation following Tonsillectomy May Be Inadequate Due to Silent Death

The focus on the first 24 hours of care for respiratory events following tonsillectomy may be misplaced and a broader focus is warranted. Nocturnal hypoxemia, an elevated apnea-hypopnea index, or obstructive sleep apnea contributes to an increased sensitivity to narcotics and postoperative complications. Narcotic pain management depresses respiration through an increase in the frequency of central sleep apnea, decreased minute ventilation, increased hypercarbia pressure, and a decrease in the hypoxic ventilator response. Residual pain gives some margin of safety as it stimulates respiration. Children dying following tonsillectomy do so silently during sleep, often without arousing the attention of caregivers or nursing personnel in close proximity. Perioperative education of caregivers, use of the least morbid surgical technique, and the control of pain rather than its elimination are prudent steps in the management of tonsillectomy patients.

Somnambulism: clinical aspects and pathophysiological hypotheses

Somnambulism, or sleepwalking, can give rise to a wide range of adverse consequences and is one of the leading causes of sleep-related injury. Accurate diagnosis is crucial for proper management and imperative in an ever-increasing number of medicolegal cases implicating sleep-related violence. Unfortunately, several widely held views of sleepwalking are characterised by key misconceptions, and some established diagnostic criteria are inconsistent with research findings. The traditional idea of somnambulism as a disorder of arousal might be too restrictive and a comprehensive view should include the idea of simultaneous interplay between states of sleep and wakefulness. Abnormal sleep physiology, state dissociation, and genetic factors might explain the pathophysiology of the disorder.

Cardiopulmonary complications during pediatric seizures: a prelude to understanding SUDEP

PURPOSE

Sudden unexpected death in epilepsy (SUDEP) is an important, unexplained cause of death in epilepsy. Role of cardiopulmonary abnormalities in the pathophysiology of SUDEP is unclear in the pediatric population. Our objective was to assess cardiopulmonary abnormalities during epileptic seizures in children, with the long-term goal of identifying potential mechanisms of SUDEP.

METHODS

We prospectively recorded cardiopulmonary functions using pulse-oximetry, electrocardiography (ECG), and respiratory inductance plethysmography (RIP). Logistic regression was used to evaluate association of cardiorespiratory findings with seizure characteristics and demographics.

KEY FINDINGS

We recorded 101 seizures in 26 children (average age 3.9 years). RIP provided analyzable data in 78% and pulse-oximetry in 63% seizures. Ictal central apnea was more prevalent in patients with younger age (p = 0.01), temporal lobe (p < 0.001), left-sided (p < 0.01), symptomatic generalized (p = 0.01), longer duration seizures (p < 0.0002), desaturation (p < 0.0001), ictal bradycardia (p < 0.05), and more antiepileptic drugs (AEDs; p < 0.01), and was less prevalent in frontal lobe seizures (p < 0.01). Ictal bradypnea was more prevalent in left-sided (p < 0.05), symptomatic generalized seizures (p < 0.01), and in brain magnetic resonance imaging (MRI) lesions (p < 0.1). Ictal tachypnea was more prevalent in older-age (p = 0.01), female gender (p = 0.05), frontal lobe (p < 0.05), right-sided seizures (p < 0.001), fewer AEDs (p < 0.01), and less prevalent in lesional (p < 0.05) and symptomatic generalized seizures (p < 0.05). Ictal bradycardia was more prevalent in male patients (p < 0.05) longer duration seizures (p < 0.05), desaturation (p = 0.001), and more AEDs (p < 0.05), and was less prevalent in frontal lobe seizures (p = 0.01). Ictal and postictal bradycardia were directly associated (p < 0.05). Desaturation was more prevalent in longer-duration seizures (p < 0.0001), ictal apnea (p < 0.0001), ictal bradycardia (p = 0.001), and more AEDs (p = 0.001).

SIGNIFICANCE

Potentially life-threatening cardiopulmonary abnormalities such as bradycardia, apnea, and hypoxemia in pediatric epileptic seizures are associated with predictable patient and seizure characteristics, including seizure subtype and duration.

Upgrading the sleeping brain with targeted memory reactivation

A fundamental feature of human memory is the propensity for beneficial changes in information storage after initial encoding. Recent research findings favor the possibility that memory consolidation during sleep is instrumental for actively maintaining the storehouse of memories that individuals carry through their lives. The information that ultimately remains available for retrieval may tend to be that which is reactivated during sleep. A novel source of support for this idea comes from demonstrations that neurocognitive processing during sleep can benefit memory storage when memories are covertly cued via auditory or olfactory stimulation. Investigations of these subtle manipulations of memory processing during sleep can help elucidate the mechanisms of memory preservation in the human brain.

Modulation of γ and spindle-range power by slow oscillations in scalp sleep EEG of children

Deep sleep is characterized by slow waves of electrical activity in the cerebral cortex. They represent alternating down states and up states of, respectively, hyperpolarization with accompanying neuronal silence and depolarization during which neuronal firing resumes. The up states give rise to faster oscillations, notably spindles and gamma activity which appear to be of major importance to the role of sleep in brain function and cognition. Unfortunately, while spindles are easily detectable, gamma oscillations are of very small amplitude. No previous sleep study has succeeded in demonstrating modulations of gamma power along the time course of slow waves in human scalp EEG. As a consequence, progress in our understanding of the functional role of gamma modulation during sleep has been limited to animal studies and exceptional human studies, notably those of intracranial recordings in epileptic patients. Because high synaptic density, which peaks some time before puberty depending on the brain region (Huttenlocher and Dabholkar, 1997), generates oscillations of larger amplitude, we considered that the best chance to demonstrate a modulation of gamma power by slow wave phase in regular scalp sleep EEG would be in school-aged children. Sleep EEG was recorded in 30 healthy children (aged 10.7 ± 0.8 years; mean ± s.d.). Time-frequency analysis was applied to evaluate the time course of spectral power along the development of a slow wave. Moreover, we attempted to modify sleep architecture and sleep characteristics through automated acoustic stimulation coupled to the occurrence of slow waves in one subset of the children. Gamma power increased on the rising slope and positive peak of the slow wave. Gamma and spindle activity is strongly suppressed during the negative peak. There were no differences between the groups who received and did not receive acoustic stimulation in the sleep parameters and slow wave-locked time-frequency analysis. Our findings show, for the first time in scalp EEG in humans, that gamma activity is associated with the up-going slope and peak of the slow wave. We propose that studies in children provide a uniquely feasible opportunity to conduct investigations into the role of gamma during sleep.

Impact of wind turbine sound on annoyance, self-reported sleep disturbance and psychological distress

PURPOSE OF THE RESEARCH

The present government in the Netherlands intends to realize a substantial growth of wind energy before 2020, both onshore and offshore. Wind turbines, when positioned in the neighborhood of residents may cause visual annoyance and noise annoyance. Studies on other environmental sound sources, such as railway, road traffic, industry and aircraft noise show that (long-term) exposure to sound can have negative effects other than annoyance from noise. This study aims to elucidate the relation between exposure to the sound of wind turbines and annoyance, self-reported sleep disturbance and psychological distress of people that live in their vicinity. Data were gathered by questionnaire that was sent by mail to a representative sample of residents of the Netherlands living in the vicinity of wind turbines

PRINCIPAL RESULTS

A dose-response relationship was found between immission levels of wind turbine sound and selfreported noise annoyance. Sound exposure was also related to sleep disturbance and psychological distress among those who reported that they could hear the sound, however not directly but with noise annoyance acting as a mediator. Respondents living in areas with other background sounds were less affected than respondents in quiet areas.

MAJOR CONCLUSIONS

People living in the vicinity of wind turbines are at risk of being annoyed by the noise, an adverse effect in itself. Noise annoyance in turn could lead to sleep disturbance and psychological distress. No direct effects of wind turbine noise on sleep disturbance or psychological stress has been demonstrated, which means that residents, who do not hear the sound, or do not feel disturbed, are not adversely affected.

A novel therapy for REM sleep behavior disorder (RBD)

STUDY OBJECTIVES

RBD may result in sleep related injury (SRI) particularly if a patient exits the bed during dream enactment behavior (DEB). The complex auditory processing and low arousal threshold of REM sleep offers a therapeutic window to halt behavior prior to SRI. We evaluated whether a recorded message prevents SRI in medically refractory RBD.

DESIGN

Case Series.

SETTING

Sleep disorders center.

PATIENTS

Four consecutive RBD patients with continued SRI despite both clonazepam and melatonin therapy.

INTERVENTION

A pressurized bed alarm customized with a familiar voice to deliver a calming message during vigorous DEB.

MEASUREMENTS AND RESULTS

The RBDQ-HK evaluated RBD symptoms, and SRI was further quantified with a new clinical tool, the Minnesota Parasomnia Injury Scale. All patients reported a decrease in RBD symptoms and SRI. No injuries occurred post-intervention. Pre-treatment: 5 serious events (SE), 80 minor events (ME), and 193 near events (NE) were noted over 66 patient-months (4.21 events/pt-mo). Post-treatment: 0 SE, 0 ME, and 3 NE were noted after a follow up period of 63 pt-months (0.05 event/pt-mo). There were 176 total bed alarm interventions (2.79 interventions/pt-mo). No adverse effects were reported, and all 4 patients described a minimal burden of treatment. RBD symptoms improved as the average RBDQ-HK score decreased from 68 (range: 53-80) to 54 (range 42-65).

CONCLUSION

A customized bed alarm may be an effective method to prevent SRI in RBD. This intervention is most suitable for cases of medically refractory RBD and/or for those patients who are unable to tolerate medical therapy.

Pediatric Obstructive Sleep Apnea Syndrome: Time to Wake Up

Pediatric patients with well-controlled OSA present few difficulties for routine dental treatment. However, patients with untreated or undiagnosed OSA can present the dental practitioner with multiple issues and challenges. Dental professionals have a unique doctor-patient relationship that affords them a role in recognizing sleep disorders by exploring the history of patients who are sleepy.

Aim: This paper is aimed at providing comprehensive review of pediatric obstructive sleep apnea.

How to cite this article: Arali V, Namineni S, Sampath Ch, Pediatric Obstructive Sleep Apnea Syndrome: Time to Wake Up. Int J Clin Pediatr Dent 2012;5(1):54-60.

Auditory arousal responses and thresholds during REM and NREM sleep of sleepwalkers and controls

BACKGROUND

It has been suggested that sleepwalkers are more difficult to awaken from sleep than are controls. However, no quantified comparisons have been made between these two populations. The main goal of this study was to assess arousal responsiveness via the presentation of auditory stimuli (AS) in sleepwalkers and controls during normal sleep and recovery sleep following sleep deprivation.

METHODS

Ten adult sleepwalkers and 10 age-matched control subjects were investigated. After a screening night, participants were presented with AS during slow-wave sleep (SWS), REM, and stage 2 sleep either during normal sleep or daytime recovery sleep following 25 h of sleep deprivation. The AS conditions were then reversed one week later.

RESULTS

When compared to controls sleepwalkers necessitated a significantly higher mean AS intensity (in dB) to induce awakenings and arousal responses during REM sleep whereas the two groups' mean values did not differ significantly during SWS and stage 2 sleep. Moreover, when compared to controls sleepwalkers had a significantly lower mean percentage of AS that induced arousal responses during REM sleep while the opposite pattern of results was found during SWS.

CONCLUSIONS

The data indicate that sleepwalkers have a higher auditory awakening threshold than controls, but only for REM sleep. These findings may reflect a compensatory mechanism of the homeostatic process underlying sleep regulation during sleepwalkers' REM sleep in reaction to their difficulties maintaining consolidated periods of NREM sleep.

Randomized, double-blind clinical trial of two different modes of positive airway pressure therapy on adherence and efficacy in children

STUDY OBJECTIVES

To determine the effects of bilevel positive airway pressure with pressure release technology (Bi-Flex) on adherence and efficacy in children and adolescents compared to standard continuous positive airway pressure (CPAP) therapy. We hypothesized that Bi-Flex would result in improved adherence but similar efficacy to CPAP.

METHODS

This was a randomized, double-blinded clinical trial. Patients with obstructive sleep apnea were randomized to CPAP or Bi-Flex. Repeat polysomnography was performed on pressure at 3 months. Objective adherence data were obtained at 1 and 3 months.

RESULTS

56 children and adolescents were evaluated. There were no significant differences in the number of nights the device was turned on, or the mean number of minutes used at pressure per night for CPAP vs Bi-Flex (24 ± 6 vs 22 ± 9 nights, and 201 ± 135 vs 185 ± 165 min, respectively, for Month 1). The apnea hypopnea index decreased significantly from 22 ± 21/h to 2 ± 3/h on CPAP (p = 0.005), and 18 ± 15/h to 2 ± 2/h on Bi-Flex (p < 0.0005), but there was no significant difference between groups (p = 0.82 for CPAP vs Bi-Flex). The Epworth Sleepiness Scale decreased from 8 ± 5 to 6 ± 3 on CPAP (p = 0.14), and 10 ± 6 to 5 ± 5 on Bi-Flex (p < 0.0005; p = 0.12 for CPAP vs Bi-Flex).

CONCLUSIONS

Both CPAP and Bi-Flex are efficacious in treating children and adolescents with OSAS. However, adherence is suboptimal with both methods. Further research is required to determine ways to improve adherence in the pediatric population.

Sleep Disturbances in Pediatric Depression

Depressive illness beginning early in life can have serious developmental and functional consequences. Therefore, understanding its etiology and pathophysiology during this developmental stage is critical for developing effective prevention and intervention strategies. There is considerable evidence of sleep alterations in adult major depressive disorder. However, studies in children and adolescents have not found consistent changes in sleep architecture paralleling adult depression. This review article summarizes sleep polysomnography research in early-onset depression, highlighting the factors associated with variable findings across studies. In addition, potential avenues for future research will be suggested in order to develop more comprehensive theoretical models and interventions for pediatric depression.

Covert waking brain activity reveals instantaneous sleep depth

The neural correlates of the wake-sleep continuum remain incompletely understood, limiting the development of adaptive drug delivery systems for promoting sleep maintenance. The most useful measure for resolving early positions along this continuum is the alpha oscillation, an 8–13 Hz electroencephalographic rhythm prominent over posterior scalp locations. The brain activation signature of wakefulness, alpha expression discloses immediate levels of alertness and dissipates in concert with fading awareness as sleep begins. This brain activity pattern, however, is largely ignored once sleep begins. Here we show that the intensity of spectral power in the alpha band actually continues to disclose instantaneous responsiveness to noise—a measure of sleep depth—throughout a night of sleep. By systematically challenging sleep with realistic and varied acoustic disruption, we found that sleepers exhibited markedly greater sensitivity to sounds during moments of elevated alpha expression. This result demonstrates that alpha power is not a binary marker of the transition between sleep and wakefulness, but carries rich information about immediate sleep stability. Further, it shows that an empirical and ecologically relevant form of sleep depth is revealed in real-time by EEG spectral content in the alpha band, a measure that affords prediction on the order of minutes. This signal, which transcends the boundaries of classical sleep stages, could potentially be used for real-time feedback to novel, adaptive drug delivery systems for inducing sleep.

Sleep and sleepiness in children with nocturnal enuresis

STUDY OBJECTIVES

To assess if sleep patterns and sleepiness are compromised in children with nocturnal enuresis (NE), in comparison with normal control subjects, and to evaluate the role of enuresis-related events during sleep.

DESIGN

Assessment of natural sleep patterns at home in a sample of children referred to enuresis clinics and controls.

SETTING

Children's homes.

PARTICIPANTS

Thirty-two children (19 boys and 13 girls aged 5.1 to 9.1 years) who suffer from primary NE and 94 healthy control subjects (49 boys and 45 girls aged 5 to 8.58 years).

INTERVENTIONS

N/A.

MEASUREMENTS AND RESULTS

Sleep measures were derived from 3 to 5 nights of actigraphy and daily logs. Additional information on events related to enuresis and daytime sleepiness was collected using daily reports. Children with NE slept significantly worse than did the control subjects. Their compromised sleep patterns were reflected in a higher number of actigraphic nighttime awakenings, the reduced percentages of motionless sleep, the higher number of reported nighttime awakening, and the increased sleep latency. Children with NE also reported higher levels of sleepiness in the morning and in the evening.

CONCLUSIONS

Compared with the sleep of control subjects, the natural sleep of children with NE is significantly more fragmented, and the children with NE experience higher levels of daytime sleepiness. This phenomenology is associated with bedwetting episodes and attempts to keep the child dry during the night. These findings may suggest that children with NE suffer from sleep fragmentation, which may explain their higher arousal threshold. These findings have clinical implications for enuresis management.

Spontaneous brain rhythms predict sleep stability in the face of noise

Quality sleep is an essential part of health and well-being. Yet fractured sleep is disturbingly prevalent in our society, partly due to insults from a variety of noises [1]. Common experience suggests that this fragility of sleep is highly variable between people, but it is unclear what mechanisms drive these differences. Here we show that it is possible to predict an individual's ability to maintain sleep in the face of sound using spontaneous brain rhythms from electroencephalography (EEG). The sleep spindle is a thalamocortical rhythm manifested on the EEG as a brief 11-15 Hz oscillation and is thought to be capable of modulating the influence of external stimuli [2]. Its rate of occurrence, while variable across people, is stable across nights [3]. We found that individuals who generated more sleep spindles during a quiet night of sleep went on to exhibit higher tolerance for noise during a subsequent, noisy night of sleep. This result shows that the sleeping brain's spontaneous activity heralds individual resilience to disruptive stimuli. Our finding sets the stage for future studies that attempt to augment spindle production to enhance sleep continuity when confronted with noise.

Obstructive sleep apnea syndrome in children: Epidemiology, pathophysiology, diagnosis and sequelae

The prevalence of pediatric obstructive sleep apnea syndrome (OSAS) is approximately 3% in children. Adenotonsillar hypertrophy is the most common cause of OSAS in children, and obesity, hypotonic neuromuscular diseases, and craniofacial anomalies are other major risk factors. Snoring is the most common presenting complaint in children with OSAS, but the clinical presentation varies according to age. Agitated sleep with frequent postural changes, excessive sweating, or abnormal sleep positions such as hyperextension of neck or abnormal prone position may suggest a sleep-disordered breathing. Night terror, sleepwalking, and enuresis are frequently associated, during slow-wave sleep, with sleep-disordered breathing. Excessive daytime sleepiness becomes apparent in older children, whereas hyperactivity or inattention is usually predominant in younger children. Morning headache and poor appetite may also be present. As the cortical arousal threshold is higher in children, arousals are not easily developed and their sleep architectures are usually more conserved than those of adults. Untreated OSAS in children may result in various problems such as cognitive deficits, attention deficit/hyperactivity disorder, poor academic achievement, and emotional instability. Mild pulmonary hypertension is not uncommon. Rarely, cardiovascular complications such as cor pulmonale, heart failure, and systemic hypertension may develop in untreated cases. Failure to thrive and delayed development are serious problems in younger children with OSAS. Diagnosis of pediatric OSAS should be based on snoring, relevant history of sleep disruption, findings of any narrow or collapsible portions of upper airway, and confirmed by polysomnography. Early diagnosis of pediatric OSAS is critical to prevent complications with appropriate interventions.

Arousal from sleep mechanisms in infants

Arousals from sleep allow sleep to continue in the face of stimuli that normally elicit responses during wakefulness and also permit awakening. Such an adaptive mechanism implies that any malfunction may have clinical importance. Inadequate control of arousal in infants and children is associated with a variety of sleep-related problems. An excessive propensity to arouse from sleep favors the development of repeated sleep disruptions and insomnia, with impairment of daytime alertness and performance. A lack of an adequate arousal response to a noxious nocturnal stimulus reduces an infant's chances of autoresuscitation, and thus survival, increasing the risk for Sudden Infant Death Syndrome (SIDS). The study of arousability is complicated by many factors including the definition of an arousal; the scoring methodology; the techniques used (spontaneous arousability versus arousal responses to endogenous or exogenous stimuli); and the confounding factors that complicate the determination of arousal thresholds by changing the sleeper's responses to a given stimulus such as prenatal drug, alcohol, or cigarette use. Infant age and previous sleep deprivation also modify thresholds. Other confounding factors include time of night, sleep stages, the sleeper's body position, and sleeping conditions. In this paper, we will review these different aspects for the study of arousals in infants and also report the importance of these studies for the understanding of the pathophysiology of some clinical conditions, particularly SIDS.

Sleep classification according to AASM and Rechtschaffen and Kales: effects on sleep scoring parameters of children and adolescents

Recently, the new American Academy of Sleep Medicine (AASM) rules and the old Rechtschaffen and Kales (R&K) criteria for sleep scoring have been shown to produce significantly different results in adults. The aim of this study was to describe in detail such differences in a group of normal children. Polysomnographic recordings from 45 healthy children (18 females and 27 males) aged between 3 and 16 years were scored following both systems and the results compared. Several significant differences between the two scoring systems were found: N1 (AASM) was significantly higher than S1 (R&K) while Stages N2 and R (AASM) were significantly smaller than S2 and rapid eye movement (R&K). The Kendall Tau correlation coefficient revealed a relatively low concordance between the two systems for the scoring of number of stage shifts per hour, minutes and percentage of Stage N1/S1, and of a percentage of Stage S2/N2. The significant differences between R&K and AASM scoring systems suggest taking some caution in adopting the new scoring criteria in children; these might be shown to be potentially useful if careful selection of the appropriate indicators derived from this new method is carried out, such as the percentage of N1 and the number of stage shifts, which are measures very sensitive to the occurrence of arousals in the new AASM system.

Sex hormones, sleep, and core body temperature in older postmenopausal women

STUDY OBJECTIVES

Assessment of relationships between polysomnographic sleep, sex hormones, and core body temperature in postmenopausal women.

DESIGN AND PARTICIPANTS

Ten women aged 57 to 71 years, at least 5 years past menopause.

SETTING

Laboratory of Human Chronobiology at Weill Cornell Medical College.

INTERVENTIONS

N/A.

MEASUREMENTS AND RESULTS

Lower estradiol (E2) and higher luteinizing hormone (LH) levels were significantly correlated with indices of poor sleep quality. Relationships between LH and polysomnographic variables were more robust than those for E2. Significant increases from basal LH levels (i.e., LH pulses) occurred more frequently after sleep onset than prior to sleep onset, and 30 of 32 of these LH pulses occurred prior to long awakenings from sleep. In addition, higher body core temperature prior to and during sleep was significantly correlated with poorer sleep efficiency and higher LH levels.

CONCLUSIONS

Most investigations of relationships between sleep, sex hormones, and body temperature have focused on perimenopausal women, menopausal phenomena such as hot flashes, the role of declining estrogen, and treatment with exogenous estrogen. The current results suggest that altered levels of both sex steroids and gonadotropins may contribute to sleep disturbance in older women and confirm the results of previous studies indicating that higher body core temperature is associated with poorer sleep quality, even in women without vasomotor symptoms. The findings also raise the possibility of alternate treatment avenues for menopause- and age-related sleep disturbance that focus on altering LH levels.

The significance of ASDA arousals in children

Sleep disorders are common in children. The sleep disturbances associated with these disease processes may impact neurodevelopment and result in daytime behavioral and cognitive changes. Currently, there are no precise methods to accurately assess sleep disruption in the pediatric age group. There is evidence that American Sleep Disorders Association (ASDA) arousals are insufficient markers of sleep disruption in children. Other techniques that have been used to assess sleep disruption include unconventional means of evaluating the electroencephalogram (EEG) during sleep and evaluating subcortical or autonomic activation. The aim of this review is to discuss the application of conventional and unconventional markers of sleep disruption in children.

Pulse transit time and blood pressure changes following auditory-evoked subcortical arousal and waking of infants

STUDY OBJECTIVES

To establish a normal range of data in 3-month-old infants in relation to changes in cardiovascular measurements, with particular reference to pulse transit time (PTT), following subcortical arousals and awakenings from sleep.

DESIGN

Prospective study.

SETTING

Sleep laboratory, Dunedin Hospital

PARTICIPANTS

Twenty healthy infants aged 9-12 weeks.

METHODS

Nap studies were performed using a standard polysomnographic setup with the addition of a Portapres blood pressure (BP) cuff (wrist application) and a piezoelectric sensor on the foot. PTT was measured from the ECG-R waveform to the arrival of the pulse peripherally. Infants were exposed to white noise from 50 to 100 dB at 10 dB intervals within REM and NREM sleep.

RESULTS

Awakening thresholds were higher (P = 0.01) in NREM (>90 dB) than REM sleep (mean +/- SD; 74.3 +/- 9.4dB). Subcortical thresholds were always 10 dB below waking thresholds. Following awakening, there was an immediate increase in HR, SBP, and DBP of 21%, 14%, and 17%, respectively, and a 13% decrease in PTT returning to baseline within 25-30 seconds. PTT at baseline measured 140 +/- 11 and 139 +/- 9 msec in NREM and REM sleep, respectively, and decreased approximately 20 msec with waking. PTT changes were negatively correlated with heart rate (HR) but not BP, although a trend was evident.

CONCLUSIONS

At 3 months of age, infants provoked to arouse from sleep showed PTT changes that inversely mimicked BP trends, suggesting that PTT could be useful in infant studies as a marker for autonomic perturbations that occur during sleep in both clinical and research settings.

Optimizing emergency awakening to audible smoke alarms: an update

OBJECTIVE

This review examines research on arousal from sleep in an emergency. It considers whether the current smoke alarm signal is optimal for waking those most at risk of dying in a fire and, if not, how it may be improved.

BACKGROUND

The fire fatality rate during the sleeping period is approximately three times greater than at other times.

METHOD

Four key areas are reviewed: (a) the characteristics of four signals (high-frequency beeping, Temporal 3, voice, and naturalistic sounds); (b) how human characteristics alter arousal to different signals; (c) research comparing the effectiveness of different alarms in different sleeping populations; and (d) acoustical, methodological, and theoretical implications.

RESULTS

Significant risk factors for staying asleep include high levels of background noise, being a heavy sleeper, sleep deprivation, being a child, hypnotics, alcohol intoxication, and hearing impairment. The high-frequency beeping signal was significantly less effective than either a voice alarm or mixed-frequency beeping in waking selected at-risk groups.

CONCLUSION

The alternative signals were more effective in arousing various groups of sleepers than was the high-frequency signal currently used in smoke alarms.

APPLICATION

Replacement of the current smoke alarm signal with one of a lower frequency is likely to wake more people more quickly and save lives.

The nature of spontaneous sleep across adulthood

The decline in sleep quality that often accompanies aging is thought to be the consequence of alterations in both circadian and homeostatic processes widely assumed to be responsible for sleep/wake regulation. A number of experimental approaches have been used to examine various aspects of age-related sleep changes, but none has examined spontaneous sleep across the entire 24-h day. Using the 'disentrainment' protocol, we studied such sleep in young, middle-aged and older adults. All subjects exhibited polyphasic sleep patterns, characterized by relatively short intervals of both sleep and waking. Whereas, the average duration of major nighttime sleep was significantly shorter in middle-aged and older subjects than in young adults, daytime napping was essentially unaffected by age. Comparisons of sleep and circadian variables between age groups suggest differential effects on sleep of the two regulatory processes, with changes in homeostatic drive preceding those of the circadian component. These findings add to a surprisingly scant literature on the longitudinal decline in sleep quality associated with aging.