Sleep-wake regulation in preterm and term infants

Co-developing sleep-wake and sensory foundations for cognition in the human fetus and newborn

In older children and adults, cognition builds upon waking sensory experience which is consolidated during sleep. In the fetus and newborn, sensory input is instead largely experienced during sleep. The nature of these sensory inputs differs within sleep, between active and quiet sleep, as well as versus wakefulness. Here, sleep-wake organisation in the fetus and newborn is reviewed, and then its interaction with sensory inputs discussed with a focus on somatosensory and auditory modalities. Next, these ideas are applied to how neurological insults affect early development, using fetal growth restriction as a test case. Finally, the argument is made that taking account of sleep-wake state during perinatal functional neuroimaging can better index sensorimotor, language, and cognitive brain activities, potentially improving its diagnostic and prognostic value. To sum up, sensory and sleep-wake functions go hand in hand during early human development. Perturbation of these twinned functions by neurological insults may mediate later neurodevelopmental deficits. Perinatal neuroimaging has the potential to track these trajectories, feasibly identifying opportunities to therapeutically intervene.

Docosahexaenoic Acid and Sleep Quality in Very and Extreme Preterm Infants

The results regarding the association of plasma docosahexaenoic acid (DHA) levels with sleep duration conflict. This study aimed to investigate the effect of oral administration of DHA on the sleep quality of Brazilian extreme preterm infants. This cohort study is part of the Joinville Docosahexaenoic Acid Study (JoiDHA) conducted with 59 infants in Joinville, Brazil. Sleep quality was assessed using the Brief Infant Sleep Questionnaire, which consists of 12 questions about the quality of sleep the week prior to its application and was answered by the parents/guardians. Of the 59 children who participated in the study, 37 (62.7%) were supplemented with DHA and 22 (37.3%) did not receive DHA. The prevalence of poor sleep quality was higher among children with the weight status at birth <50th percentile (68.2%; p = 0.045) when compared to children ≥50th percentile. However, Poisson regression analysis showed that neither weight status at birth nor DHA use was associated with sleep quality, even after adjusting for the same variables. In summary, sleep quality 12-24 months after birth was not associated with DHA supplementation in very and extreme preterm infants. Additional studies that address the increase in DHA intake would be important for the understanding of the effect of this fatty acid on sleep quality.

Maternal Reports of Preterm and Sick Term Infants' Settling, Sleeping and Feeding in the 9 Months after Discharge from Neonatal Nursery: An Observational Study

The effects of preterm birth, neonatal morbidities and environmental influences on infant sleep development is an important yet under-researched topic, with little known about normative sleep for infants born sick or preterm. The aim of this prospective, observational longitudinal study was to evaluate maternal perceptions and degree of bother with infant sleep behaviours and feeding outcomes across the first 9 months after discharge for sick/preterm infants cared for in the neonatal intensive care unit (NICU) and for healthy term-born infants. This paper reports outcomes for the sick/preterm cohort (I = 94) that were recruited from two NICUs in Perth, Western Australia. Total bother scores were on average 20.2% higher at 9 months than at two weeks post-discharge (p < 0.001). Increased night waking frequency, evening settling duration and crying duration were all positively associated with total bother scores. Maternal confidence scores were negatively associated with maternal bother scores; with each unit increase in confidence, maternal bother decreased by 8.5% (p < 0.001). Covariates such as birth gestation, breastfeeding status and multiple births were not associated with maternal bother. Families may benefit from additional support when experiencing increased night waking frequency and crying and settling durations in the first 9 months after discharge from NICU.

Persian version of brief infant sleep questionnaire (BISQ): a psychometric evaluation

BACKGROUND

The high prevalence of sleep problems and their negative consequences on children and parents highlight the need to design early screening instruments to evaluate sleep problems in early childhood. We aimed to determine the validity and reliability of the Brief Infant Sleep Questionnaire (BISQ) among the Iranian population.

METHODS AND MATERIALS

This study included 646 one-year-old infants by random sampling from the PERSIAN birth cohort study. Following the forward-backward translation of the BISQ, its psychometric properties, including construct validity in terms of concurrent and convergent validities as well as reliability, were evaluated.

RESULTS

The CVIs and CVR ranged between 0.8 and 1.00 for all items. Therefore, we keep all the items of the original version of the BISQ in the Persian BISQ. Concurrent validity was assessed by comparing items of the Persian BISQ among different maternal views regarding their infant's sleep. All BISQ items were significantly different among the two levels of maternal view about the infant's sleep problem except daytime sleep duration. The convergent validity of the BISQ was evaluated by calculating the correlation between BISQ items and the ISQ (infant sleep questionnaire) total score as a similar tool. ISQ score was adequately correlated with nocturnal sleep latency and the number of waking at night (rs ranged from 0.59 to 0.72). In addition, the associations of mothers' and infants' demographic variables and nutritional and gestational variables with BISQ items were presented to confirm construct validity. Strong correlations were found between the repeated sleep measures for sleep arrangement, sleep position, and sleep situation (kappa ranged from 0.65 to 0.84), nocturnal sleep duration, daytime sleep duration number of wakings at night, night waking duration, nocturnal sleep latency and sleep-onset time (ICC ranged 0.91 to 0.99).

CONCLUSION

The Persian version of the BISQ is a reliable and valid measure for assessing sleep problems in infants. It would be helpful to be utilized for the early diagnosis of infants' sleep problems.

Machine Learning-Derived Active Sleep as an Early Predictor of White Matter Development in Preterm Infants

White matter dysmaturation is commonly seen in preterm infants admitted to the neonatal intensive care unit (NICU). Animal research has shown that active sleep is essential for early brain plasticity. This study aimed to determine the potential of active sleep as an early predictor for subsequent white matter development in preterm infants. Using heart and respiratory rates routinely monitored in the NICU, we developed a machine learning-based automated sleep stage classifier in a cohort of 25 preterm infants (12 females). The automated classifier was subsequently applied to a study cohort of 58 preterm infants (31 females) to extract active sleep percentage over 5-7 consecutive days during 29-32 weeks of postmenstrual age. Each of the 58 infants underwent high-quality T2-weighted magnetic resonance brain imaging at term-equivalent age, which was used to measure the total white matter volume. The association between active sleep percentage and white matter volume was examined using a multiple linear regression model adjusted for potential confounders. Using the automated classifier with a superior sleep classification performance [mean area under the receiver operating characteristic curve (AUROC) = 0.87, 95% CI 0.83-0.92], we found that a higher active sleep percentage during the preterm period was significantly associated with an increased white matter volume at term-equivalent age [β = 0.31, 95% CI 0.09-0.53, false discovery rate (FDR)-adjusted p-value = 0.021]. Our results extend the positive association between active sleep and early brain development found in animal research to human preterm infants and emphasize the potential benefit of sleep preservation in the NICU setting.

Combining Cardiorespiratory Signals and Video-Based Actigraphy for Classifying Preterm Infant Sleep States

The classification of sleep state in preterm infants, particularly in distinguishing between active sleep (AS) and quiet sleep (QS), has been investigated using cardiorespiratory information such as electrocardiography (ECG) and respiratory signals. However, accurately differentiating between AS and wake remains challenging; therefore, there is a pressing need to include additional information to further enhance the classification performance. To address the challenge, this study explores the effectiveness of incorporating video-based actigraphy analysis alongside cardiorespiratory signals for classifying the sleep states of preterm infants. The study enrolled eight preterm infants, and a total of 91 features were extracted from ECG, respiratory signals, and video-based actigraphy. By employing an extremely randomized trees (ET) algorithm and leave-one-subject-out cross-validation, a kappa score of 0.33 was achieved for the classification of AS, QS, and wake using cardiorespiratory features only. The kappa score significantly improved to 0.39 when incorporating eight video-based actigraphy features. Furthermore, the classification performance of AS and wake also improved, showing a kappa score increase of 0.21. These suggest that combining video-based actigraphy with cardiorespiratory signals can potentially enhance the performance of sleep-state classification in preterm infants. In addition, we highlighted the distinct strengths and limitations of video-based actigraphy and cardiorespiratory data in classifying specific sleep states.

Clinical value of cortical bursting in preterm infants with intraventricular haemorrhage

BACKGROUND

In healthy preterm infants, cortical burst rate and temporal dynamics predict important measures such as brain growth. We hypothesised that in preterm infants with germinal matrix-intraventricular haemorrhage (GM-IVH), cortical bursting could provide prognostic information.

AIMS

We determined how cortical bursting was influenced by the injury, and whether this was related to developmental outcome.

STUDY DESIGN

Single-centre retrospective cohort study at University College London Hospitals, UK.

SUBJECTS

33 infants with GM-IVH ≥ grade II (median gestational age: 25 weeks).

OUTCOME MEASURES

We identified 47 EEGs acquired between 24 and 40 weeks corrected gestational age as part of routine clinical care. In a subset of 33 EEGs from 25 infants with asymmetric injury, we used the least-affected hemisphere as an internal comparison. We tested whether cortical burst rate predicted survival without severe impairment (median 2 years follow-up).

RESULTS

In asymmetric injury, cortical burst rate was lower over the worst- than least-affected hemisphere, and bursts over the worst-affected hemisphere were less likely to immediately follow bursts over the least-affected hemisphere than vice versa. Overall, burst rate was lower in cases of GM-IVH with parenchymal involvement, relative to milder structural injury grades. Higher burst rate modestly predicted survival without severe language (AUC 0.673) or motor impairment (AUC 0.667), which was partly mediated by structural injury grade.

CONCLUSIONS

Cortical bursting can index the functional injury after GM-IVH: perturbed burst initiation (rate) and propagation (inter-hemispheric dynamics) likely reflect associated grey matter and white matter damage. Higher cortical burst rate is reassuring for a positive outcome.

Consensus statement on Singapore integrated 24-hour activity guide for early childhood

Introduction

Early childhood is a critical period for growth and development. Adopting healthy lifestyle behaviours during this period forms the foundation for future well-being and offers the best protection against non-communicable diseases. Singapore studies have shown that many young children are not achieving the recommendations on physical activity, sedentary behaviour and sleep. A workgroup was set up to develop recommendations for caregivers of infants, toddlers and preschoolers (aged <7 years) on how to integrate beneficial activities within a daily 24-hour period for optimal development and metabolic health.

Method

The Grading of Recommendations Assessment, Development and Evaluation (GRADE)- ADOLOPMENT approach was employed for adoption, adaption or de novo development of recommendations. International and national guidelines were used as references, and an update of the literature reviews up to September 2021 was conducted through an electronic search of PubMed, Embase and Cochrane Central Register of Controlled Trials (CENTRAL) databases.

Results

Four consensus statements were developed for each age group: infants, toddlers and preschoolers. The statements focus on achieving good metabolic health through regular physical activity, limiting sedentary behaviour, achieving adequate sleep and positive eating habits. The 13th consensus statement recognises that integration of these activities within a 24-hour period can help obtain the best results.

Conclusion

This set of recommendations guides and encourages caregivers of Singapore infants, toddlers and preschoolers to adopt beneficial lifestyle activities within each 24-hour period.

Parent Experiences in the NICU and Transition to Home

Families (n = 12) with infants born at <29 weeks gestation shared their experiences while in the NICU and transitioning home. Parents were interviewed 6-8 weeks after NICU discharge, including some during the acute phase of the COVID-19 pandemic. Findings regarding the parent experience in the NICU were focused around challenges navigating parent-infant separation, social isolation, communication difficulties, limited knowledge of preterm infants, mental health challenges. Parents also discussed supports that were present and supports they wished were present, as well as the impact of COVID-19 on their experiences. In the transition to home, primary experiences included the sudden nature of the transition, anxiety around discharge preparation, and the loss of the support from nursing staff. During the first few weeks at home, parents expressed joy and anxiety, particularly around feeding. The COVID-19 pandemic limited emotional, informational, and physical support to parents and resulted in limited mutual support from other parents of infants in the NICU. Parents of preterm infants in the NICU present with multiple stressors, rendering attending to parental mental health crucial. NICU staff need to address logistical barriers and familial priorities impacting communication and parent-infant bonding. Providing multiple opportunities for communication, participating in caretaking activities, and meeting other families can be important sources of support and knowledge for parents of very preterm infants.

Feasibility of automated early postnatal sleep staging in extremely and very preterm neonates using dual-channel EEG

OBJECTIVE

To investigate the feasibility of automated sleep staging based on quantitative analysis of dual-channel electroencephalography (EEG) for extremely and very preterm infants during their first postnatal days.

METHODS

We enrolled 17 preterm neonates born between 25 and 30 weeks of gestational age. Three-hour behavioral sleep observations and simultaneous dual-channel EEG monitoring were conducted for each infant within their first 72 hours after birth. Four kinds of representative and complementary quantitative EEG (qEEG) metrics (i.e., bursting, synchrony, spectral power, and complexity) were calculated and compared between active sleep, quiet sleep, and wakefulness. All analyses were performed in offline mode.

RESULTS

In separate comparison analyses, significant differences between sleep-wake states were found for bursting, spectral power and complexity features. The automated sleep-wake state classifier based on the combination of all qEEG features achieved a macro-averaged area under the curve of receiver operating characteristic of 74.8%. The complexity features contributed the most to sleep-wake state classification.

CONCLUSIONS

It is feasible to distinguish between sleep-wake states within the first 72 postnatal hours for extremely and very preterm infants using qEEG metrics.

SIGNIFICANCE

Our findings offer the possibility of starting personalized care dependent on preterm infants' sleep-wake states directly after birth, potentially yielding long-run benefits for their developmental outcomes.

Sleep state organisation of moderate to late preterm infants in the neonatal unit

BACKGROUND

Sleep supports neurodevelopment and sleep architecture reflects brain maturation. This prospective observational study describes the nocturnal sleep architecture of healthy moderate to late preterm (MLP) infants in the neonatal unit at 36 weeks post menstrual age (PMA).

METHODS

MLP infants, in the neonatal unit of a tertiary hospital in Ireland from 2017 to 2018, had overnight continuous electroencephalography (cEEG) with video for a minimum 12 h at 36 weeks PMA. The total sleep time (TST) including periods of active sleep (AS), quiet sleep (QS), indeterminate sleep (IS), wakefulness and feeding were identified, annotated and quantified.

RESULTS

A total of 98 infants had cEEG with video monitoring suitable for analysis. The median (IQR) of TST in the 12 h period was 7.09 h (IQR 6.61-7.76 h), 4.58 h (3.69-5.09 h) in AS, 2.02 h (1.76-2.36 h) in QS and 0.65 h (0.48-0.89 h) in IS. The total duration of AS was significantly lower in infants born at lower GA (p = 0.007) whilst the duration of individual QS periods was significantly higher (p = 0.001).

CONCLUSION

Overnight cEEG with video at 36 weeks PMA showed that sleep state architecture is dependent on birth GA. Infants with a lower birth GA have less AS and more QS that may have implications for later neurodevelopment.

IMPACT

EEG provides objective information about the sleep organisation of the moderate to late preterm (MLP) infant. Quantitative changes in sleep states occur with each week of advancing gestational age (GA). Active sleep (AS) is the dominant sleep state that was significantly lower in infants born at lower GA. MLP infants who were exclusively fed orally had a shorter total sleep time and less AS compared to infants who were fed via nasogastric tube.

Precision caffeine therapy for apnea of prematurity and circadian rhythms: New possibilities open up

Caffeine is the globally consumed psychoactive substance and the drug of choice for the treatment of apnea of prematurity (AOP), but its therapeutic effects are highly variable among preterm infants. Many of the molecular underpinnings of the marked individual response have remained elusive yet. Interestingly, the significant association between Clock gene polymorphisms and the response to caffeine therapy offers an opportunity to advance our understanding of potential mechanistic pathways. In this review, we delineate the functions and mechanisms of human circadian rhythms. An up-to-date advance of the formation and ontogeny of human circadian rhythms during the perinatal period are concisely discussed. Specially, we summarize and discuss the characteristics of circadian rhythms in preterm infants. Second, we discuss the role of caffeine consumption on the circadian rhythms in animal models and human, especially in neonates and preterm infants. Finally, we postulate how circadian-based therapeutic initiatives could open new possibilities to promote precision caffeine therapy for the AOP management in preterm infants.

Asia-Pacific consensus statement on integrated 24-hour activity guidelines for the early years

Background

Early childhood is a vital period for development and growth. Promoting beneficial lifestyle behaviours in early childhood can help optimise children's health, development and learning, shape their behaviours in adulthood and offer the best protection against future non-communicable diseases (NCDs). In the Asia-Pacific region, NCDs are significant causes of healthcare burden and mortality. Furthermore, there is also a high prevalence of adverse metabolic risk factors and unhealthy lifestyle behaviours among these children.

Method

Representatives from 19 Asia-Pacific nations and/or jurisdictions developed a consensus statement on integrated 24-hour activity guidelines for the early years using the GRADE-ADOLOPMENT framework.

Findings

These guidelines apply to all infants, toddlers and pre-schoolers below 5 years of age. The guidelines aim to provide a holistic and practical approach to lifestyle activities by framing physical activity, sedentary behaviour and sleep within a 24-hour period. Dietary patterns were included as they play an integral role in metabolic health and energy balance.

Interpretation

Aligned with the World Health Organization's Global Action Plan for the Prevention and Control of NCDs through health promotion interventions in early life, through cultivating healthy lifestyle behaviours in the children's early years, we aim to provide children with the best start in life and reduce the burden of future NCDs in the Asia-Pacific region.

Funding

Funded by Integrated platform for research in advancing metabolic health outcomes of women and children.

The Sleep Well Baby project: an automated real-time sleep–wake state prediction algorithm in preterm infants

Study Objectives

Sleep is an important driver of early brain development. However, sleep is often disturbed in preterm infants admitted to the neonatal intensive care unit (NICU). We aimed to develop an automated algorithm based on routinely measured vital parameters to classify sleep–wake states of preterm infants in real-time at the bedside.

Methods

In this study, sleep–wake state observations were obtained in 1-minute epochs using a behavioral scale developed in-house while vital signs were recorded simultaneously. Three types of vital parameter data, namely, heart rate, respiratory rate, and oxygen saturation, were collected at a low-frequency sampling rate of 0.4 Hz. A supervised machine learning workflow was used to train a classifier to predict sleep–wake states. Independent training (n = 37) and validation datasets were validation n = 9) datasets were used. Finally, a setup was designed for real-time implementation at the bedside.

Results

The macro-averaged area-under-the-receiver-operator-characteristic (AUROC) of the automated sleep staging algorithm ranged between 0.69 and 0.82 for the training data, and 0.61 and 0.78 for the validation data. The algorithm provided the most accurate prediction for wake states (AUROC = 0.80). These findings were well validated on an independent sample (AUROC = 0.77).

Conclusions

With this study, to the best of our knowledge, a reliable, nonobtrusive, and real-time sleep staging algorithm was developed for the first time for preterm infants. Deploying this algorithm in the NICU environment may assist and adapt bedside clinical work based on infants’ sleep–wake states, potentially promoting the early brain development and well-being of preterm infants.

Longitudinal Analysis of Sleep-Wake States in Neonatal Rats Subjected to Hypoxia-Ischemia

OBJECTIVE

Sleep is necessary for brain maturation in infants. Perinatal hypoxic-ischemic encephalopathy (HIE) is a major cause of chronic neurological disease in infants. Although the developmental changes of electroencephalogram (EEG) in human newborns have been described, little is known about the EEG normal maturation characteristics in rodents and the changes in sleep-awake states caused by hypoxia-ischemia (HI). This study aimed to investigate the pathological response of sleep-wake states in neonatal rats with HIE.

METHODS

We constructed HIE and sham models on postnatal day (P) 3 rats and continuously monitored them using electroencephalography and electromyography for up to P12. The distribution of sleep-wake states was analyzed to estimate the effects of HIE.

RESULTS

Compared with the sham group, the HI group showed lower rapid eye movement (REM) sleep percentage, but wake percentage and frequency was higher during P4-P12. The frequency of REM and non-rapid eye movement (NREM) sleep increased and the duration of REM and NREM sleep decreased after HI induction. However, it gradually returned to the normal level with an increase in daytime.

CONCLUSION

HI damage alters the sleep-wake patterns during early neural development. The findings provide a comprehensive assessment of serial sleep-wake state recordings in neonatal rats from P4-P12.

Prognostic value of neonatal EEG following therapeutic hypothermia in survivors of hypoxic-ischemic encephalopathy

OBJECTIVE

Early prediction of neurological deficits following neonatal hypoxic-ischemic encephalopathy (HIE) may help to target support. Neonatal animal models suggest that recovery following hypoxia-ischemia depends upon cortical bursting. To test whether this holds in human neonates, we correlated the magnitude of cortical bursting during recovery (≥postnatal day 3) with neurodevelopmental outcomes.

METHODS

We identified 41 surviving infants who received therapeutic hypothermia for HIE (classification at hospital discharge: 19 mild, 18 moderate, 4 severe) and had 9-channel electroencephalography (EEG) recordings as part of their routine care. We correlated burst power with Bayley-III cognitive, motor and language scores at median 24 months. To examine whether EEG offered additional prognostic information, we controlled for structural MRI findings.

RESULTS

Higher power of central and occipital cortical bursts predicted worse cognitive and language outcomes, and higher power of central cortical bursts predicted worse motor outcome, all independently of structural MRI findings.

CONCLUSIONS

Clinical EEG after postnatal day 3 may provide additional prognostic information by indexing persistent active mechanisms that either support recovery or exacerbate brain damage, especially in infants with less severe encephalopathy.

SIGNIFICANCE

These findings could allow for the effect of clinical interventions in the neonatal period to be studied instantaneously in the future.

In Touch with the Heartbeat: Newborns' Cardiac Sensitivity to Affective and Non-Affective Touch

The sense of touch is the first manner of contact with the external world, providing a foundation for the development of sensorimotor skills and socio-affective behaviors. In particular, affective touch is at the core of early interpersonal interactions and the developing bodily self, promoting the balance between internal physiological state and responsiveness to external environment. The aim of the present study is to investigate whether newborns are able to discriminate between affective touch and non-affective somatosensory stimulations and whether affective touch promotes a positive physiological state. We recorded full-term newborns' (N = 30) heart rate variability (HRV)-which reflects oscillations of heart rate associated with autonomic cardio-respiratory regulation-while newborns were presented with two minutes of affective (stroking) and non-affective (tapping) touch alternated with two minutes of resting in a within-subject design. The results revealed that non-affective touch elicits a decrease in HRV, whereas affective touch does not result in a change of HRV possibly indicating maintenance of calm physiological state. Thus, newborns showed cardiac sensitivity to different types of touch, suggesting that early somatosensory stimulation represents scaffolding for development of autonomic self-regulation with important implications on infant's ability to adaptively respond to the surrounding social and physical environment.

Long-range temporal organisation of limb movement kinematics in human neonates

OBJECTIVE

Movement provides crucial sensorimotor information to the developing brain, evoking somatotopic cortical EEG activity. Indeed, temporal-spatial organisation of these movements, including a diverse repertoire of accelerations and limb combinations (e.g. unilateral progressing to bilateral), predicts positive sensorimotor outcomes. However, in current clinical practice, movements in human neonates are qualitatively characterised only during brief periods (a few minutes) of wakefulness, meaning that the vast majority of sensorimotor experience remains unsampled. Here our objective was to quantitatively characterise the long-range temporal organisation of the full repertoire of newborn movements, over multi-hour recordings.

METHODS

We monitored motor activity across 2-4 h in 11 healthy newborn infants (median 1 day old), who wore limb sensors containing synchronised tri-axial accelerometers and gyroscopes. Movements were identified using acceleration and angular velocity, and their organisation across the recording was characterised using cluster analysis and spectral estimation.

RESULTS

Movement occurrence was periodic, with a 1-hour cycle. Peaks in movement occurrence were associated with higher acceleration, and a higher proportion of movements being bilateral.

CONCLUSIONS

Neonatal movement occurrence is cyclical, with periods consistent with sleep-wake behavioural architecture. Movement kinematics are organised by these fluctuations in movement occurrence. Recordings that exceed 1-hour are necessary to capture the long-range temporal organisation of the full repertoire of newborn limb movements.

SIGNIFICANCE

Future work should investigate the prognostic value of combining these movement recordings with synchronised EEG, in at-risk infants.