12^th Meeting of the European Pediatric Sleep Club

From arousals to awakenings: the development of sleep continuity in infancy and childhood

The symposium has focused on the significance of the arousals and awakenings in infancy and childhood and their impact on the development of sleep continuity. Arousability from sleep has significant clinical implications in pediatrics: excessive arousability could lead to sleep disruption and insomnia while depressed arousability is implicated in sudden infant death syndrome and in some forms of parasomnias. The analisys of arousals and of sleep microstructure is becoming crucial in order to evaluate sleep quality and the impact of different pathologies (i.e. obstructive sleep apnea) on sleep organization and on daytime neurobehavioral functioning.

It is expected that this approach will contribute to the understanding of several clinical conditions such as insomnia, parasomnias, respiratory disturbances during sleep, sudden infant death syndrome, etc.

We discussed the topic with the following presentations:

Early steps of the awakening process

F. Giganti & P. Salzarulo

 This contribution aimed at to summarize available information on the developmental trend of spontaneous awakenings from preterm infants to infants up to their first year of life and to propose useful guidelines for future researches.

No changes with age, between 33 and 40 weeks of postconceptional age, for number as well as for duration of awakenings have been observed. The decrease in the number of spontaneous awakenings starts at term age and proceeds over the first year of life. There is no significant change with age in the duration of awakenings; the most frequent state which precedes awakenings is REM sleep both in preterm infants and in infants born at term age.

The process of awakenings at early ages should be further investigated. The role of homeostatic and circadian components as well as their interaction at each developmental step should be explored. Moreover, behavioural and physiological investigations concerning the semiology of sleep-wake transitions are necessary. Finally, characteristics of autonomic variables preceding awakening as well as motor aspects should be explored as a function of age.

Arousals in infants: scoring methodology and clinical implications

Patricia Franco, José Groswasser, André Kahn

Arousals have direct implications in various clinical conditions. An excessive propensity to arouse is found in infants suffering from insomnia and sleep disruptions, that are potentially associated with impairment of development. An insufficient propensity to arouse could lower the chance to survive in infants exposed to noxious conditions during sleep, possibly increasing the risk for infant sudden death. In adults, arousal is defined using standard criteria laid out by the American Disorders Association (ASDA 1992). Infants, during the first year of life, have a maturational process of EEG activity and sleep structure. Hence, the use of the ASDA’s definition is poorly appropriate for infants. The International Pediatric Wake-Up Club was set up with the aim to define a method for the scoring of arousals in infants, based on the analysis of polygraphic sleep-wake recordings.

The present document focuses on the arousals of healthy infants, born at term, and studied between the ages of 1 and 12 months of life. Since some features of arousals in infants depend on maternal, infant and experimental factors, experimental conditions should be reported.

Optimal and minimal conditions are reported as the choice of the method depends on local considerations.

The techniques recommended for the recording of arousals included EEGs, EOGs, chin EMG, breathing and cardiac parameters, body and limb movements. Some techniques are useful for the recording of the causes and/or effects of arousals such as nasal airflow, oxygen saturation, tibialis anterior electrodes, esophageal pH probe.

Arousals reflect the activation of various structures, from subcortical to cortical areas.

A subcortical activation or a cortical arousal are differentiated.

A subcortical activation is scored if no change in EEG is seen, but at least two of the following changes are apparent during at least 3 sec, such as

1) gross body movements,

2) changes in heart rate,

3) changes in breathing pattern in NREM sleep or increase in chin EMG amplitude in REM sleep.

A cortical arousal is scored using the above criteria, with in addition, an abrupt change in EEG background frequency (of at least 1 Hz). A decrease in EEG amplitude can help identify cortical arousals.

Baseline sleep state should be established during 30 s epoch. At  least 10 s of uninterrupted state is required between subcortical activations or cortical arousals. The duration of the reference period should be described.

Cortical arousals and subcortical activations are subdivided in two major categories:

- spontaneous (no stimulus can be identified);

- induced (following an identifiable stimulus).

Great care must be taken to control the environment stability and exclude inadvertent arousals from stimuli (e.g., noise, light, tactile stimuli, nursing intervention, or room drafts).

Unresolved issues are discussed such as the magnitude of EEG, cardiac and breathing changes, the best techniques used for the evaluation of EEG changes, the differentiation of cortical arousals from subcortical activations in the presence of movement artefacts on EEG channels.

For future investigations, the International Pediatric Wake-Up Club can try to resolve these unresolved issues and to validate the definition of arousal in other age groups as newborns (term or preterm) or children; or in specific clinical conditions.

Sleep organization and continuity in children aged 3 - 6 years

Marie Jo Challamel

 Dr. Challamel presented preliminary data on arousals in obstructive sleep apnea children showing that, while sleep macrostructure was similar to control children, major differences has been found for microstructure and highlighted the correlation of apneas with arousals. Twenty healthy children, aged between 2 years and 4 years 6 months (mean 3 yrs 3 months) with adeno-tonsillar hypertrophy but without any underlying medical condition, neuromuscular disease, obesity or craniofacial abnormalities have been recorded polygraphically during a complete nocturnal sleep with 3 EEGs, 2 EOGs, 1 chin EMG, Thoracic, abdominal and sum signals from inductive plethysmography, oronasal flow by thermistance and end tidal CO2, diaphragmatic, abdominal and tibial EMGs. Arterial oxyhemoglobine was measured by pulse oxymetry. Sleep was scored according to Rechtschaffen and Kales criteria. This study has dealt with the analysis of the macro and micro structure of sleep in 10 children with severe SAOS (OAI h/TST: 11.4 (4.6), desaturation Index h/TST: 9.4 (12.4)) as compared to 10 children without SAOS (OAI  h/TST: 0.1 (0.3), Desaturation Index h/TST: 0.2 (0.3)). There is no consensus for a definition of arousals in children, we used the ASDA definition modified by Mograss and al. (1). Arousals of more than one second were taken into account. Stastistical analysis were done with SPSS, comparisons between the 2 groups by U-test Mann-Whitney; P < 0.05.

This study confirms the absence of any significant differences for the macrostructure of sleep in children (2, 3). In infants sleep disordered breathing is associated with a decrease in REM sleep.

 There was  also no differences for the frequency of arousals between 15 and 60 sec per hour of TST: 18.1 (9.9) versus 19.7 (10.1) and for the number of awakening > 60 sec per hour of sleep: 6.6 (5.1) versus 6.6 (3.3). On the other hand, it shows significant differences concerning the microstructure of sleep with arousals between 1 and 15 seconds, significantly more frequent in children with SAOS than in children without: 25.4 (14.8) versus 8.8 (2.4), P<0.001.  These microarousals were significantly more frequent during REM sleep when compared to non-REM sleep in the two groups. The same results has been shown in older children by Scholle (3) and by Goh (2) using in Goh‘s study the ASDA definition. This preliminary study emphasizes the importance of the fragmentation of sleep in children with OSAS; it put the stress on the need for a consensus for a definition of EEG and movement arousals in children.

1- Mograss MA, Ducharme FM, Brouillette RT. Movement/arousals. Description, classification and relationship to sleep apnea in children. Am J Crit Care Med 1994; 150 : 1690- 1696.

2- Goh DY, Galster P, Marcus CL. Sleep and respiratory disturbances in children with obstructive sleep apnea. Am J respir Crit Care Med  2000 ; 162 : 682-686.

3- Scholle S, Zwacka G. Arousals and obstructive sleep apnea syndrome in children. Clin Neurophysiol 2001; 112 : 984-991.

Arousals in school age-children: analysis of sleep microstructure

Oliviero Bruni

CAP reflects different levels of arousal during NREM and is represented by subtypes phases A1, A2 and A3. A1 can be considered as cortical activation while A2 and A3 are more close to arousals as defined by ASDA (1992).

Methods: CAP parameters were quantified in 10 normal healthy subjects (6 males and 4 females, mean age 8.3 years; range 6–10 years). All subjects underwent polysomnography recordings for two consecutive nights in a standard laboratory setting. Sleep data were stored on computer using a 16-channel polysomnography digital system. Sleep macrostructure was visually scored according to the criteria by Rechtschaffen and Kales (Brain Information Service/Brain Research Institute, University of California, Los Angeles, 1968); CAP was visually scored following the criteria by Terzano et al. (Sleep Med 2 (2001) 537).

Results: CAP rate showed a progressive increase with the deepness of sleep, with high values during slow wave sleep (SWS). CAP time showed its longest duration during non-REM (NREM) sleep stage 2 (S2), followed by SWS and sleep stage 1 (S1). No differences across NREM sleep stages were found for CAP cycle and phase B mean duration; on the contrary, phase A showed longer duration during SWS than in S1 and S2. Phases A1 were the most numerous (84.45%) followed by A3 (9.14%) and by A2 (6.44%). The distribution of phases A subtypes across NREM stages showed significant differences for the A1 subtypes that occurred more frequently during SWS than in S2 and S1 (and during S2 than in S1). Subtypes A3 were more frequent during S1 than SWS while no differences were found for subtype A2. The analysis of A1 interval distribution showed a log-normal-like distribution with a peak around 25 s for the A1 phases and no clear peak for A2–A3 phases.

Conclusions: The analysis of CAP in school-age children is characterized by an increase of CAP rate during SWS and a high percentage of A1 phases. The distribution of interval between consecutive A1 phases showed a peak around 25 s.

Professor Gregory Stores

The restorative value of sleep depends on its duration, timing and also its quality. There is debate about the definition of sleep quality with recent emphasis on continuity including the rate of arousals in overnight sleep. In adults, sleep discontinuity (or “fragmentation”) induced experimentally or occurring in such sleep disorders as obstructive sleep apnoea has been linked with daytime underfunctioning and behavioural disturbance. Reports suggest that generally children have a low rate of arousals compared with adults. Nevertheless, high levels of discontinuity are seen in certain conditions. The question arises: Are high levels of sleep discontinuity in childhood associated with psychological impairments comparable to those described in adults?

Present study: Home PSG and psychometric assessments of cognition, mood and behaviour were available for disorders (nocturnal asthma, atopic dermatitis, chronic fatigue syndrome) shown by previously published studies to be characterised by frequent awakenings (and ASDA defined brief arousals in the asthma group) and psychological deficits. Mean age was 11.5 years (range 5-17). Possible relationships between PSG measures of discontinuity and psychological impairment were explored in various ways: direct correlational analysis; comparisons between children showing age-corrected fragmentation levels above and below normal values and comparisons between the upper and lower thirds of the arousal rate distribution. No consistent relationships were seen in any of these analyses between sleep discontinuity measures and psychological impairment.

Conclusion: Further more detailed and large scale studies are required to explore further the relationships between sleep discontinuity and impaired psychological function in children. Important issues include different definitions of discontinuity, adequacy of psychological measures of real-life functioning and behaviour, as well as the relative contributions of sleep discontinuity and other factors which influence a child's psychological state at any one point in time.