Sleep architecture in term and preterm infants beyond the neonatal period: the influence of gestational age, steroids, and ventilatory support

STUDY OBJECTIVE: To examine (1) sleep architecture of infants at varied risk for sudden infant death syndrome, (2) delays or advances in preterm infants at term postmenstrual age, (3) whether ventilatory support and gestational age alter sleep, (4) whether steroids alter sleep, (5) confounding influences of sex, small for gestational age, and maternal smoking. DESIGN: Overnight polysomnography. Dependent variables: Percentage of active sleep, quiet sleep, indeterminate, and awake time per total recording time; mean and longest duration of state epochs; number of episodes > or = 10 minutes; and sleep efficiency. SETTING: Collaborative Home Infant Monitoring Evaluation (CHIME). PARTICIPANTS: Two hundred one preterm and 198 term infants between 33 and 58 weeks postmenstrual age during polysomnography. Fifty-one term infants with an apparent life-threatening event without known etiology (apnea of infancy), 59 subsequent siblings of babies who died of sudden infant death syndrome, and 88 healthy term infants. RESULTS: Tracings of infants with apnea of infancy and healthy term infants were similar. Subsequent siblings of babies who died of sudden infant death syndrome spent less time in quiet sleep. Preterm infants (< or = 37 weeks postmenstrual age) exhibited immature architecture compared with infants of term postmenstrual age. The latter exhibited similar sleep except that they had a lower percentage of quiet sleep and longer mean indeterminate and longest indeterminate episodes. Preterm infants with the youngest gestational age lagged behind older preterm infants. Neither sex nor use of steroids affected sleep. Assisted ventilation was associated with a delay in maturation, small-for-gestational age status with increased active sleep, and smoking with increased awake time. CONCLUSION: With few exceptions, asymptomatic premature infants do not exhibit significant delays in sleep architecture compared with term infants at comparable postmenstrual age. The preterm infant with an early gestational age and morbidity exhibited delayed sleep architecture.     

The maturation of correlations between cardiac and respiratory measures across sleep states in normal infants.

Coordination of cardiac and respiratory measures is not mature in newborn infants but develops during early life. The course of that development is assessed in this study. Twelve-hour recordings of electrocardiogram, electroencephalogram, digastric electromyogram, electrooculogram and expired CO2 were obtained from 25 normal infants at 1 week and 1, 2, 3, 4 and 6 months of age. Each 1-minute epoch was classified as quiet sleep, rapid eye movement (REM) sleep, waking or indeterminate state. In each sleep-waking state, the correlations of heart rate with respiratory rate, heart rate with respiratory rate variability and respiratory rate with its own variability were determined on a minute-by-minute basis for each recording. The relative extents of correlations between measures and the maturational trends of these correlations were profoundly influenced by sleep-waking state. During quiet sleep, two of the three correlations weakened significantly over the first month of life, but, in the waking state, the same correlations strengthened over this period. During quiet sleep and waking, the three correlations showed similar patterns of development, but the three showed dissimilar developmental trends during REM sleep. These dissimilarities may reflect changes in the nature of REM sleep consequent to myelination of rostral brain pathways.     

Sleep organization in the first year of life: developmental trends in the quiet sleep-paradoxical sleep cycle

The night sleep of 48 healthy drug-free infants, aged 1-54 weeks, was recorded and analysed in order to show how cycles contribute to sleep episode organization and how the balance among different sleep states (i.e. quiet sleep, paradoxical sleep and ambiguous sleep) within cycles changes as a function of age. A greater proportion of time spent in cycles (TCT) on total sleep time (TST), as a result of the lengthening of sleep cycles, was found in older infants, whereas sleep out of cycles decreases with age. The internal structure of the sleep cycles also changes with age, because of the increase in the proportion of quiet sleep (QS), the appearance of slow wave sleep (SWS) from the 21st week onwards, and the decrease in ambiguous sleep. The proportion of paradoxical sleep (PS), however, remains stable throughout the first year of age. The improvement of sleep organization across the first year of life is paralleled by an internal restructuring of the cycle, involving mainly changes in QS. We may speculate that both changes, one involving the lengthening of cycle and the other involving the increase in QS component, contribute to the improvement of biological and psychological sleep functions during development.     

Sex differences in the ontogeny of sleep apnea during the first year of life

Respiration and behavioral sleep states were studied in full term, normal infants under natural circumstances over the first year of life. Sixteen male and 12 female infants were observed during an interfeeding period in the hospital at 2 days of age; in the home during a 7-hr period whenever the infants were put down to nap on weeks 2, 3, 4, and 5; and in the home during the first 2 hr of overnight sleep at 3, 6, and 12 months of age. From analog recordings of respiration, all apneic episodes, or respiratory pauses, of 2 sec or longer were measured. Analyses of these data were made for active and quiet sleep states separately. During active sleep, female infants had higher frequencies of apneic episodes and greater total duration of apnea during observations at all ages through 6 months of age; during quiet sleep females had greater frequency and duration of apnea through 3 months of age. The two sexes did not differ with respect to the mean length of apneic episodes in either sleep state. However, females had longer single apneic episodes in both sleep states throughout the first year. The two sexes also differed in their predictability of apnea levels. Female infants were predictable at all ages from one observation to another throughout the first year of life. For the male infants, there were significant correlations within the first 5 weeks and between 6 months and 12 months; however, the correlations from between the first 5 weeks and 6 months were not significant. The results of this study of infants during naturally occurring sleep periods indicate a differential ontogeny of apnea in normal male and female infants. Females had higher levels of apnea and more predictable apnea characteristics than males through 6 months of age. These early sex differences in respiratory function may have implications for the occurrence of SIDS, which has the highest incidence during the first 6 months of life.     

Arousals induced by proximal esophageal reflux in infants.

We investigated whether acid reflux in the proximal esophagus can induce arousal from sleep in infants. Fifty normal infants with occasional regurgitations were studied at the age of 8 weeks (range 4-26 weeks). In each child a pH probe was placed in the proximal portion of the thoracic esophagus, in front of the third vertebra, under radiologic control. Polygraphic monitoring of state of alertness and of proximal esophageal pH changes was recorded continuously during one night. The data were analyzed blind. For 41 of the 50 infants, a total of 97 drops below pH 4 was computed. Reflux was more frequently associated with wakefulness (41% of the episodes), or rapid eye movement (REM) sleep (39%), than with nonREM (19%) or indeterminate sleep (1%). Comparing the fifth and the last minutes preceding the pH drops, a significant increase in the number of behavioral arousals was observed (p = 0.003). In comparison with the minute before the drop in esophageal pH, a further significant increase in the number of arousals occurred during the first minutes following the pH drop (p = 0.001). Although the first minutes following the 97 episodes of reflux represented only 0.4% of the total sleep time, 76% of all arousals (74 out of 97) took place during this time period (p = 0.001). Five minutes after the pH drops, the behavioral changes tended to return to prereflux values. It is concluded that in infants, during sleep, proximal gastroesophageal reflux can act as a strong arousal stimulus.     

Relative treatment rates for sleep disorders and sleep disturbances following abortion and childbirth: a prospective record-based study

Sleep disorders are linked with mood disorders and other psychiatric illnesses. Many women attribute sleep difficulties to abortion, but this self-diagnosis has not been tested using record-based evidence. Examination of records for 56,824 women with no known history of sleep disorders or sleep disturbances revealed that women were more likely to be treated for sleep disorders or disturbances following an induced abortion compared to a birth. The difference was most pronounced in the first 180 days after pregnancy resolution and was not significant after the third year.     

Schlaf im Säuglingsalter

Good sleep first needs to be learned. Not all infants manage this by themselves; some need the support of their parents. In order for this to succeed or for regulatory disorders to be intercepted, knowledge and good advice from a competent source are required. The widely available parenting books on the subject of children’s sleep, which are frequently read by desperate parents, are often not sufficient to ensure adequate information on the relationships between sleep and self-regulation. More decisive is competent counseling from medically trained specialist staff. It is important to know and be able to explain the physiological changes of sleep during the first year of life.     

Maternal depressed mood moderates the impact of infant sleep on mother–infant bonding

Parent–infant bonding has long-term consequences for the psychological wellbeing of the child. Considering the centrality of infant sleep patterns in infant–caregiver interactions in the first year of life, we propose that infant sleep patterns act as a catalyst or disruptor for mother–infant relationship, such that infant sleep patterns contribute to maternal mood, maternal sleep quality, perception of infant temperament, and her bonding experience. One hundred fifty-two Israeli mothers, of 5–8-month-old infants, responded to Internet-based questionnaires regarding their sleep, their mood, their infant’s sleep, the infant’s temperament, and their bonding experience. Eight percent of the mothers reported clinically significant depression, while 67 % reported significant sleep difficulties. Infant sleep difficulties correlated with maternal mood and sleep quality, infant fussiness, and bonding. Structural equation modeling demonstrated that maternal sleep partially mediated the relationship between infant sleep and maternal mood. Additionally, 22 % of the variance in bonding was explained by infant sleep problems and temperament. Notably, maternal depression moderated this effect such that infant sleep problems correlated with bonding only in those mothers who were depressed. The results suggest that infant sleep is a vector by which maternal cognitions and mood are transmitted to her child, with long-term implications for psychological development.     

Sleep problems: predictor or outcome of media use among emerging adults at university?

The pervasiveness of media use in our society has raised concerns about its potential impact on important lifestyle behaviours, including sleep. Although a number of studies have modelled poor sleep as a negative outcome of media use, a critical assessment of the literature indicates two important gaps: (i) studies have almost exclusively relied on concurrent data, and thus have not been able to assess the direction of effects; and (ii) studies have largely been conducted with children and adolescents. The purpose of the present 3‐year longitudinal study, therefore, was to examine whether both sleep duration and sleep problems would be predictors or outcomes of two forms of media use (i.e. television and online social networking) among a sample of emerging adults. Participants were 942 (71.5% female) university students (M = 19.01 years, SD = 0.90) at Time 1. Survey measures, which were assessed for three consecutive years starting in the first year of university, included demographics, sleep duration, sleep problems, television and online social networking use. Results of a cross‐lagged model indicated that the association between sleep problems and media use was statistically significant: sleep problems predicted longer time spent watching television and on social networking websites, but not vice versa. Contrary to our hypotheses, sleep duration was not associated with media use. Our findings indicate no negative effects of media use on sleep among emerging adults, but instead suggest that emerging adults appear to seek out media as a means of coping with their sleep problems.     

Sleep-wake state organization, neonatal assessment and development in premature infants during the first year of life. II

Twenty four premature infants were evaluated in their homes at seven ages during the first year of life to determine whether sleep-wake state organization was related to either neonatal assessment or short-term developmental outcome measures. A model assessing environmental and biological influences on the maturational course of selected sleep-wake state parameters was also evaluated. Sleep-wake state variables and neonatal assessment items were related to each other, and both predicted developmental quotients at 6 months and 1 year of age. Concordance was present primarily in the domain of motor activities. Waking motor behaviors and motor activity in sleep seem to independently reflect an infant's level of developmental organization. Individual sleep-wake state variables were influenced by both biological and environmental factors during maturation. The developmental course of quiet sleep is primarily biologically determined, as evidenced by its relationship to the infant's birth status (gestational age or birth weight); the infant's behavior that results in being taken from the crib during the night, and the course of his/her sleep that occurs between midnight and morning are dependent on both biological factors (perhaps infant irritability), and post-birth experiences (perhaps the caregiver's response to infant irritability). The course of active sleep and wakefulness are dependent solely on environmental influences, and not on maturity at birth.     

Children's sleep under the threat of attack by ballistic missiles

The present paper reports on the influence of the Scud missile attacks during the Gulf War on the sleep of Israeli children. Two studies were performed. In the first, sleep habits and sleep disturbances of 61 (mean age 20 months) infants were assessed by questionnaires completed by their parents 5 months before the war and immediately after the end of the War. Comparison of pre- and post-war data revealed no major changes in sleep habits or in sleep quality. In the second study, sleep of 55 children was monitored at home by actigraphs during the last month of the War. All children were aroused during missile attacks, but returned to sleep immediately, with no evidence of carry-over effects once the 'all clear' sign was given. Comparison of sleep quality measures obtained during the War with those of age- and sex-matched children monitored a year before the war did not reveal any significant differences apart from the immediate response to the attack.     

The role of slow-wave sleep on the duration of quiet sleep in infants

The duration of quiet sleep (QS) phases has been shown to increase during the first year of life. Slow-wave sleep (SWS) appears in about half of the QS phases beyond 20 weeks. In order to evaluate the role of SWS in the lengthening of QS phase duration during the first year of life, we looked at 48 normal full-term infants (aged between 1 and 54 weeks), recorded for a whole-night period. Records included electro-encephalogram (EEG) and other polygraphic parameters. Infants were separated into two groups: (1) those who did not show SWS episodes at all, and (2) those who show both QS phases with (QS SWS+) and without (QS SWS-) SWS episodes. In group 2 the duration of QS SWS+ was longer than that of QS SWS, as well as longer than that of QS of group 1. Group 1 had a duration of QS phases similar to that of QS SWS-. The duration of QS SWS+ depended both on the SWS latency and SWS duration. The lengthening of QS phases with age is accounted for by those phases containing SWS episodes, reflecting a maturational restructuring of QS.     

Sleep architecture and continuity measures of neonates with chronic lung disease.

Electroencephalographic (EEG) sleep studies of 25 preterm neonates with chronic lung disease (CLD) corrected to a fullterm postconceptional age were compared with recordings from two groups of neonates without CLD: a fullterm appropriate for gestational age group (9 patients) and a preterm group studied at a corrected term postconceptional age (15 patients). Electrographic/polygraphic studies were obtained using 21-channel EEG recordings. Scores were tabulated based on minute-by-minute visual analyses of sleep state, number and duration of arousals, body movements and rapid eye movements (REM). A significant reduction in the percentage of active sleep was noted in the CLD group compared to both control groups (31.15% vs. 47.01% and 52.9%, respectively). The mean percentage of indeterminate sleep was significantly increased in the study group as compared to both control groups (31.23% vs. 15.18% and 11.5%). In addition, significant differences were noted between the CLD group and the healthy preterm control group with respect to the number (0.29/minute vs. 0.13/minute) and duration (4.8 seconds vs. 2.94 seconds) of arousals as well as the total number of body movements (1.57/minute vs. 0.74/minute). These data suggest that neurophysiological organization of the immature brain, as reflected in neonatal sleep architecture and continuity measures, is adversely affected in neonates with CLD. EEG sleep architecture and continuity measures may be helpful in predicting the longitudinal outcome of infants with CLD as this group is at risk for adverse neurodevelopmental outcome.     

Sleep and waking states in infancy: normative studies

Twelve-hour polygraphic recordings were obtained in 20 normal healthy term infants at 1 week of age, at monthly intervals up to 4 months, and at 6 months of age. Each minute of these recordings was coded into active sleep (AS), quiet sleep (QS), wakefulness (AW), or indeterminate (IN) based on polygraphic and behavioral variables. For each state, a dozen variables were computed with the help of a laboratory computer. Together these variables describe trends in the development of sleep and wakefulness in the laboratory: an increase in QS and a concomitant decrease in AS, an increase in sustained episodes of these states, and continuous sleep onset in AS throughout this time span. Considerable variability appears to characterize immature sleep patterns, but a reduction in variability was noted between 3 and 4 months of age. The number of sustained sleep-state episodes and the percentage of AS and IN proved to be stable characteristics of individual infants. The large variability among and within infants sheds doubt on the usefulness of polygraphic monitoring of sleep states for early detection of abnormalities.     

Mental health, parental rules and sleep in pre-adolescents

A health-sleep model concerning the relationship of mental health and parental rules with time in bed and sleep quality has been developed on the basis of survey data collected from 448 children in the first trimester of the regular school year. The children had a mean age of about 11 years and were attending last two grades of primary school. The relations between mental health characteristics, parental rules concerning sleep, sleep environment, sleep quality and time in bed are analysed using a structural equation model. In addition to a latent variable for 'mental health', two uncorrelated latent variables had to be introduced for sleep to achieve a satisfactory fit. One latent variable is related to sleep quality (restorative sleep), and the other relates to lying awake in bed prior to sleep (awake in bed). Restorative sleep shows a strong relationship with mental health, and awake in bed is related to having an own bedroom.     

Polysomnographic sleep and waking states are similar in subsequent siblings of SIDS and control infants during the first six months of life

Twenty-five subsequent siblings of infants who died of Sudden Infant Death Syndrome (SIDS) underwent 12-h overnight polygraphic recordings during the first week of life and at 1, 2, 3, 4, and 6 months of age. The polygraphic tracings from these infants were compared with those from 25 infants without a family history of SIDS. One dozen sleep and waking parameters were examined including state transition probabilities, the ratio between quiet sleep (QS) and active sleep (AS), the incidence and duration of sustained states and the stability of an infant's sleep and waking during the first half year of life. Variability within and between infants was marked with a reduction of variability in measures of QS at 3 months and of AS at 4 months of age. The similarities between subsequent siblings of SIDS and control infants far outweighted the differences. However, subsequent siblings exhibited a tendency, once asleep, to remain asleep longer than controls. This finding was observed in a comparison of 20 infants in each group. When five infants were added to each group, infants in both groups tended to awaken equally from QS, but once in AS the subsequent siblings tended to proceed into QS instead of awaken as the controls did.     

The use of actigraphy for assessment of the development of sleep/wake patterns in infants during the first 12 months of life

Maturation of sleep/wake patterns is one of the most important physiological developments during the first year of life. In this study, we aimed to compare the use of actigraphy and parental sleep diaries (SD) for recording the development of sleep/wake patterns longitudinally in term infants in their own home environments over the first 12 months of life. Twenty healthy term infants (7F/13M) were studied for 3 days each month in their own homes over the first 12 months of life. Sleep/wake patterns were recorded using both SD and actigraphy (AW) (AW64, Mini Mitter Co. Inc., Sunriver, OR, USA). The development of sleep and wake was analysed over 24 h, during the day (08:00-20:00 hours) and during the night (20:00-08:00 hours). A total of 186 studies had complete data sets for both analysis methods. Overall, there was no difference between methods of measurement for determination of the total percentage of sleep or wake over 24 h, or for the total percentage of sleep or wake during the day. However, at night, AW scored less time asleep (73.3 +/- 0.9%) and more time awake (26.7 +/- 0.9%) compared with the SD (80.7 +/- 1.04% and 19 +/- 1.0%, respectively, P < 0.001). Mean percentage sleep during the day decreased from 51% at 1 month to 28% at 12 months with the 1-month values being significantly higher than all other ages, while mean percentage sleep at night was only different between 1 month and 11 and 12 months. In conclusion actigraphy provides a useful tool for assessing the development infant sleep.     

Expert-system classification of sleep/waking states in infants

This work is part of a project to develop an expert system for automated classification of the sleep/waking states in human infants; i.e. active or rapid-eye-movement sleep (REM), quiet or non-REM sleep (NREM), including its four stages, indeterminate sleep (IS) and wakefulness (WA). A model to identify these states, introducing an objective formalisation in terms of the state variables characterising the recorded patterns, is presented. The following digitally recorded physiological events are taken into account to classify the sleep/waking states: predominant background activity and the existence of sleep spindles in the electro-encephalogram; existence of rapid eye movements in the electro-oculogram; and chin muscle tone in the electromyogram. Methods to detect several of these parameters are described. An expert system based on artificial ganglionar lattices is used to classify the sleep/waking states, on an off-line minute-by-minute basis. Algorithms to detect patterns automatically and an expert system to recognise sleep/waking states are introduced, and several adjustments and tests using various real patients are carried out. Results show an overall performance of 96.4% agreement with the expert on validation data without artefacts, and 84.9% agreement on validation data with artefacts. Moreover, results show a significant improvement in the classification agreement due to the application of the expert system, and a discussion is carried out to justify the difficulties of matching the expert's criteria for the interpretation of characterising patterns.     

Expert-system classification of sleep/waking states in infants

This work is part of a project to develop an expert system for automated classification of the sleep/waking states in human infants; i.e. active or rapid-eye-movement sleep (REM), quiet or non-REM sleep (NREM), including its four stages, indeterminate sleep (IS) and wakefulness (WA). A model to identify these states, introducing an objective formalisation in terms of the state variables characterising the recorded patterns, is presented. The following digitally recorded physiological events are taken into account to classify the sleep/waking states: predominant background activity and the existence of sleep spindles in the electro-encephalogram; existence of rapid eye movements in the electro-oculogram; and chin muscle tone in the electromyogram. Methods to detect several of these parameters are described. An expert system based on artificial ganglionar lattices is used to classify the sleep/waking states, on an off-line minute-by-minute basis. Algorithms to detect patterns automatically and an expert system to recognise sleep/waking states are introduced, and several adjustments and tests using various real patients are carried out. Results show an overall performance of 96.4% agreement with the expert on validation data without artefacts, and 84.9% agreement on validation data with artefacts. Moreover, results show a significant improvement in the classification agreement due to the application of the expert system, and a discussion is carried out to justify the difficulties of matching the expert's criteria for the interpretation of characterising patterns.