Development of fetal and neonatal sleep and circadian rhythms

REM refines and rescues memory representations: a new theory

Despite extensive evidence on the roles of nonrapid eye movement (NREM) and REM sleep in memory processing, a comprehensive model that integrates their complementary functions remains elusive due to a lack of mechanistic understanding of REM's role in offline memory processing. We present the REM Refining and Rescuing (RnR) Hypothesis, which posits that the principal function of REM sleep is to increase the signal-to-noise ratio within and across memory representations. As such, REM sleep selectively enhances essential nodes within a memory representation while inhibiting the majority (Refine). Additionally, REM sleep modulates weak and strong memory representations so they fall within a similar range of recallability (Rescue). Across multiple NREM-REM cycles, tuning functions of individual memory traces get sharpened, allowing for integration of shared features across representations. We hypothesize that REM sleep's unique cellular, neuromodulatory, and electrophysiological milieu, marked by greater inhibition and a mixed autonomic state of both sympathetic and parasympathetic activity, underpins these processes. The RnR Hypothesis offers a unified framework that explains diverse behavioral and neural outcomes associated with REM sleep, paving the way for future research and a more comprehensive model of sleep-dependent cognitive functions.

Combining developmental and sleep health measures for autism spectrum disorder screening: an ECHO study

BACKGROUND

Sleep problems are reported for up to 80% of autistic individuals. We examined whether parsimonious sets of items derived from the Modified Checklist for Autism in Toddlers, Revised (M-CHAT-R) and the Brief Infant Sleep Questionnaire (BISQ) are superior to the standard M-CHAT-R in predicting subsequent autism spectrum disorder (ASD) diagnoses.

METHODS

Participants from 11 Environmental influences on Child Health Outcomes (ECHO) cohorts were included. We performed logistic LASSO regression models with 10-fold cross-validation to identify whether a combination of items derived from the M-CHAT-R and BISQ are superior to the standard M-CHAT-R in predicting ASD diagnoses.

RESULTS

The final sample comprised 1552 children. The standard M-CHAT-R had a sensitivity of 44% (95% CI: 34, 55), specificity of 92% (95% CI: 91, 94), and AUROC of 0.726 (95% CI: 0.663, 0.790). A higher proportion of children with ASD had difficulty falling asleep or resisted bedtime during infancy/toddlerhood. However, LASSO models revealed parental reports of sleep problems did not improve the accuracy of the M-CHAT-R in predicting ASD diagnosis.

CONCLUSION

While children with ASD had higher rates of sleep problems during infancy/toddlerhood, there was no improvement in ASD developmental screening through the incorporation of parent-report sleep metrics.

IMPACT

Parental-reported sleep problems are common in autism spectrum disorder (ASD). We investigated whether the inclusion of parental-reports of infant/toddler sleep patterns enhanced the effectiveness of developmental screening for autism. We reported higher rates of difficulty falling asleep and resisting bedtime during infancy and toddlerhood among children later diagnosed with ASD; however, we did not find an improvement in ASD developmental screening through the incorporation of parent-report sleep metrics. In our sample, the standard M-CHAT-R had a sensitivity of 39% among children of mothers with government insurance compared with a sensitivity of 53% among children of mothers with employer-based insurance.

Characteristics and Transition of Sleep-Wake Rhythm in Nursery School Children: The Importance of Nocturnal Sleep

In this study, we investigated the sleep-wake rhythm of nursery school children with the aim of supporting their health and mental/physical development. We analyzed 4881 children from infancy to 6 years of age, using 2 week sleep tables recorded by their guardians. The tables contained night bedtimes, wake times, nighttime/daytime sleep duration, and the differences in these between weekdays and weekends. The total sleep decrement of children with increasing age is attributed to a decrease in daytime sleep, while nighttime sleep duration remains almost unchanged at about 10 h, which is, therefore, referred to as the nighttime basic sleep duration (NBSD). Although bedtime stabilizes at around 9:30 p.m. by the age of 2, wake-up times tend to be before 7 a.m., which results in sleep insufficiency during weekdays. This lack of sleep is compensated for by long naps on weekdays and by catching up on sleep on weekend mornings, which may contribute to future social jet lag. Guardians are encouraged to know their children's exact NBSD and set an appropriate bedtime to be maintained on weekdays. This helps to prevent sleep debt and fosters a consistent daily rhythm of waking up at the same time both on weekdays and weekends. These conditions are believed to support mental/physical development and school and social adaptation.

The association between infant sleep, cognitive, and psychomotor development: a systematic review

STUDY OBJECTIVES

To synthesize findings of original articles examining the association between sleep-wake patterns of typically developing infants aged 0 to 18 months and cognitive and psychomotor development.

METHODS

A systematic search strategy was used to identify articles assessing the association between infant sleep (0 to 18 months) and cognitive/psychomotor development (Medline, PsycINFO, and SCOPUS). Of 7136 articles screened, 22 articles met inclusion criteria, and the results were subsequently synthesized. A quality assessment was conducted, and studies were categorized as "poor," "fair," or "good."

RESULTS

Out of 22 studies, 2 found exclusively significant associations (SAs) between infant sleep and cognitive/psychomotor development, 2 found no SAs and 17 found mixed results (MRs). Studies with exclusively significant results used a single sleep variable and single timepoint designs. Studies finding MRs or no SAs used multiple sleep, developmental variables, or multi-timepoint designs. Eight out of 10 studies and 7 out of 8 studies investigating nocturnal and total sleep duration, respectively, found no SA with developmental outcomes. While 63% of studies were rated as having good methodological quality, all studies but one had an estimated power of less than 0.80.

CONCLUSIONS

Findings of this review do not support conclusive associations between sleep-wake patterns in infancy and cognitive/psychomotor development. This conclusion contrasts with the literature in older populations, questioning if the association between sleep and development is of a different nature in infancy, potentially because of brain maturation. More studies including larger samples will be needed to clarify the presence or absence of such an association.

Sleep as a driver of pre- and postnatal brain development

In 1966, Howard Roffwarg proposed the ontogenic sleep hypothesis, relating neural plasticity and development to rapid eye movement (REM) sleep, a hypothesis that current fetal and neonatal sleep research is still exploring. Recently, technological advances have enabled researchers to automatically quantify neonatal sleep architecture, which has caused a resurgence of research in this field as attempts are made to further elucidate the important role of sleep in pre- and postnatal brain development. This article will review our current understanding of the role of sleep as a driver of brain development and identify possible areas for future research. IMPACT: The evidence to date suggests that Roffwarg's ontogenesis hypothesis of sleep and brain development is correct. A better understanding of the relationship between sleep and the development of functional connectivity is needed. Reliable, non-invasive tools to assess sleep in the NICU and at home need to be tested in a real-world environment and the best way to promote healthy sleep needs to be understood before clinical trials promoting and optimizing sleep quality in neonates could be undertaken.

Remote data collection of infant activity and sleep patterns via wearable sensors in the HEALthy Brain and Child Development Study (HBCD)

The HEALthy Brain and Child Development (HBCD) Study, a multi-site prospective longitudinal cohort study, will examine human brain, cognitive, behavioral, social, and emotional development beginning prenatally and planned through early childhood. Wearable and remote sensing technologies have advanced data collection outside of laboratory settings to enable exploring, in more detail, the associations of early experiences with brain development and social and health outcomes. In the HBCD Study, the Novel Technology/Wearable Sensors Working Group (WG-NTW) identified two primary data types to be collected: infant activity (by measuring leg movements) and sleep (by measuring heart rate and leg movements). These wearable technologies allow for remote collection in the natural environment. This paper illustrates the collection of such data via wearable technologies and describes the decision-making framework, which led to the currently deployed study design, data collection protocol, and derivatives, which will be made publicly available. Moreover, considerations regarding actual and potential challenges to adoption and use, data management, privacy, and participant burden were examined. Lastly, the present limitations in the field of wearable sensor data collection and analysis will be discussed in terms of extant validation studies, the difficulties in comparing performance across different devices, and the impact of evolving hardware/software/firmware.

Mapping the physiological changes in sleep regulation across infancy and young childhood

Sleep patterns in infancy and early childhood vary greatly and change rapidly during development. In adults, sleep patterns are regulated by interactions between neuronal populations in the brainstem and hypothalamus, driven by the circadian and sleep homeostatic processes. However, the neurophysiological mechanisms underlying the sleep patterns and their variations across infancy and early childhood are poorly understood. We investigated whether a well-established mathematical model for sleep regulation in adults can model infant sleep characteristics and explain the physiological basis for developmental changes. By fitting longitudinal sleep data spanning 2 to 540 days after birth, we inferred parameter trajectories across age. We found that the developmental changes in sleep patterns are consistent with a faster accumulation and faster clearance of sleep homeostatic pressure in infancy and a weaker circadian rhythm in early infancy. We also find greater sensitivity to phase-delaying effects of light in infancy and early childhood. These findings reveal fundamental mechanisms that regulate sleep in infancy and early childhood. Given the critical role of sleep in healthy neurodevelopment, this framework could be used to pinpoint pathophysiological mechanisms and identify ways to improve sleep quality in early life.

Circadian rhythm development in preterm infants. The role of postnatal versus postmenstrual age

BACKGROUND, AIMS

Circadian rhythm maturation may be disturbed in premature infants undergoing neonatal intensive care. We used continuous heart rate recordings across the entire neonatal intensive care period to study circadian rhythm development in preterm infants and to evaluate the roles of postmenstrual (PMA) versus postnatal age (PNA).

MATERIALS AND METHODS

The circadian rhythm was calculated using a cosine fit of heart rate. The circadian rhythm amplitudes were averaged weekly and studied relative to PMA and PNA using the linear mixed effects models, adjusting for clinical variables that could affect the heart rate. The daily circadian rhythms were used to create grand averages for PMA groups: ≤31, 32-35, and > 35 weeks, and for PNA groups: ≤30, 31-60, and > 60 days.

RESULTS

Sixty-six infants were evaluated as part of an ongoing prospective study with gestational ages between 23 and 36 weeks. The PMA (1.47 × 10-2 beats per minute (bpm)/week, P = 2.07 × 10-8) and PNA (1.87 × 10-2 bpm/day; P = 1.86 × 10-6) were significantly associated with the circadian rhythm amplitude independent of covariates. Infants ≤31 weeks' PMA and ≤30 days PNA, the phase of circadian rhythm amplitude grand averages showed a peak at night and a nadir during the day. Hereafter the circadian rhythm phase reversed to that established for mature individuals. The highest circadian rhythm amplitudes present >35 weeks' PMA and > 60 days PNA.

CONCLUSIONS

Our results indicate circadian rhythm matures with advancing gestation. The reversed circadian rhythm phase during the early postnatal period could be due to premature exposure to the ex-utero environment and warrant further study.

Made to move: A review of measurement strategies to characterize heterogeneity in normal fetal movement

Fetal movement is a crucial indicator of fetal well-being. Characteristics of fetal movement vary across gestation, posing challenges for researchers to determine the most suitable assessment of fetal movement for their study. We summarize the current measurement strategies used to assess fetal movement and conduct a comprehensive review of studies utilizing these methods. We critically evaluate various measurement approaches including subjective maternal perception, ultrasound, Doppler ultrasound, wearable technology, magnetocardiograms, and magnetic resonance imaging, highlighting their strengths and weaknesses. We discuss the challenges of accurately capturing fetal movement, which is influenced by factors such as differences in recording times, gestational ages, sample sizes, environmental conditions, subjective perceptions, and characterization across studies. We also highlight the clinical implications of heterogeneity in fetal movement assessment for monitoring fetal behavior, predicting adverse outcomes, and improving maternal attachment to the fetus. Lastly, we propose potential areas of future research to overcome the current gaps and challenges in measuring and characterizing abnormal fetal movement. Our review contributes to the growing body of literature on fetal movement assessment and provides insights into the methodological considerations and potential applications for research.

Generalized Camera-Based Infant Sleep-Wake Monitoring in NICUs: A Multi-Center Clinical Trial

The infant sleep-wake behavior is an essential indicator of physiological and neurological system maturity, the circadian transition of which is important for evaluating the recovery of preterm infants from inadequate physiological function and cognitive disorders. Recently, camera-based infant sleep-wake monitoring has been investigated, but the challenges of generalization caused by variance in infants and clinical environments are not addressed for this application. In this paper, we conducted a multi-center clinical trial at four hospitals to improve the generalization of camera-based infant sleep-wake monitoring. Using the face videos of 64 term and 39 preterm infants recorded in NICUs, we proposed a novel sleep-wake classification strategy, called consistent deep representation constraint (CDRC), that forces the convolutional neural network (CNN) to make consistent predictions for the samples from different conditions but with the same label, to address the variances caused by infants and environments. The clinical validation shows that by using CDRC, all CNN backbones obtain over 85% accuracy, sensitivity, and specificity in both the cross-age and cross-environment experiments, improving the ones without CDRC by almost 15% in all metrics. This demonstrates that by improving the consistency of the deep representation of samples with the same state, we can significantly improve the generalization of infant sleep-wake classification.

Disruption of Circadian Sleep/Wake Rhythms in Infants May Herald Future Development of Autism Spectrum Disorder

We investigated whether the abnormal rhythms in infants are related to the future development of autism spectrum disorder (ASD), using a questionnaire from September to October 2016. The parents of 160 children with ASD (male, n = 123; female, n = 37) were recruited from two hospitals in K and H cities, and as a control group, 145 children (male, n = 75; female, n = 70) were recruited from four nursery schools in T city. The associations between ASD and bedtime and waking time on weekdays and weekends in infancy (<1 years of age), at 1-3 years, and at 3-5 years of ages were studied using a multivariable logistic regression analysis. In particular, at <3 years of age, the following factors were associated with an increased prevalence of ASD in the future: (1) short sleep periods (<8 h); (2) taking a long time to fall asleep (>60 min); (3) sleep beginning after 22:00; (4) a wake-up time after 08:00; and (5) frequent (>3 times) and long-term awakening periods (>60 min). The misalignment and/or shift of the circadian rhythm in infants may be one of the precursors and/or risk factors for the future development of ASD.

A Sequential End-to-End Neonatal Sleep Staging Model with Squeeze and Excitation Blocks and Sequential Multi-Scale Convolution Neural Networks

Automatic sleep staging offers a quick and objective assessment for quantitatively interpreting sleep stages in neonates. However, most of the existing studies either do not encompass any temporal information, or simply apply neural networks to exploit temporal information at the expense of high computational overhead and modeling ambiguity. This limits the application of these methods to multiple scenarios. In this paper, a sequential end-to-end sleep staging model, SeqEESleepNet, which is competent for parallelly processing sequential epochs and has a fast training rate to adapt to different scenarios, is proposed. SeqEESleepNet consists of a sequence epoch generation (SEG) module, a sequential multi-scale convolution neural network (SMSCNN) and squeeze and excitation (SE) blocks. The SEG module expands independent epochs into sequential signals, enabling the model to learn the temporal information between sleep stages. SMSCNN is a multi-scale convolution neural network that can extract both multi-scale features and temporal information from the signal. Subsequently, the followed SE block can reassign the weights of features through mapping and pooling. Experimental results exhibit that in a clinical dataset, the proposed method outperforms the state-of-the-art approaches, achieving an overall accuracy, F1-score, and Kappa coefficient of 71.8%, 71.8%, and 0.684 on a three-class classification task with a single channel EEG signal. Based on our overall results, we believe the proposed method could pave the way for convenient multi-scenario neonatal sleep staging methods.

Use of Light Protection Equipment at Night Reduces Time Until Discharge From the Neonatal Intensive Care Unit: A Randomized Interventional Study

Newborn infants' circadian systems are not completely developed and rely on external temporal cues for synchronizing their biological rhythms to the environment. In neonatal intensive care units (NICUs), lighting is usually continuous or irregular and infants are exposed to artificial light at night, which can have negative health consequences. Therefore, the aim of this study was to evaluate the impact of the use of individual light protection equipment at night on the development and growth of preterm neonates. Infants born at less than 37 gestational weeks who no longer needed constant intensive care were admitted into a newborn nursery and randomized to either use eye masks at night (intervention, n = 21) or not (control, n = 20). Infants who used eye protection at night were discharged earlier than those in the control group (8 [5] vs 12 [3.75] days; p < 0.05). A greater variation within the day in heart rate was observed in the intervention group, with lower values of beats per minute at 1400 and 2000 h. There was no significant difference in weight gain between groups. In view of our results and of previous findings present in the literature, we suggest that combining a darkened environment at night with individual light protection devices creates better conditions for the development of preterm infants in the NICU. In addition, eye masks are an affordable and simple-to-use tool that can reduce hospitalization costs by decreasing the number of days spent in the NICU.

Sleep characteristics, early spontaneous movements, and developmental functioning in preterm infants in the early postnatal period

OBJECTIVE

This study aimed to investigate the following: (i) sleep characteristics in preterm infants at 9-20 weeks of corrected age, and (ii) differences in early spontaneous movements and developmental functioning results between the groups based on some sleep characteristics.

METHODS

Seventy-four preterm infants (36 female) were included. Sleep characteristics were assessed according to the Brief Infant Sleep Questionnaire (BISQ). The infants were divided into two groups based on total sleep duration: less than 12 h (38 infants), and 12 h and more (36 infants). Video recordings were made for the General Movements Assessment (GMA) and evaluated using the Motor Optimality Score for 3- to 5-Month-Old-Infants-Revised (MOS). Cognitive, language, and motor development were assessed using the Bayley Scales of Infant and Toddler Development, Third Edition (Bayley-III).

RESULTS

The total sleep duration of all preterm infants (mean ± SD) was 11.8 ± 3.3 h. Infants who had absent fidgety movements slept less than 12 h, and fidgety movements differed between the groups (p = 0.012). Infants who slept 12 h or more had significantly higher MOS (p = 0.041), cognitive (p = 0.002), language (p < 0.001), and motor (p = 0.002) development results. Infants who snored had lower MOS (p = 0.001), cognitive (p = 0.004), language (p = 0.002), and motor (p = 0.001) development results. Infants with fewer than three nocturnal awakenings had significantly higher Bayley-III cognitive (p = 0.007), language (p = 0.032), and motor (p = 0.005) domain results. Prone and supine sleeping positions showed higher motor domain results than lateral positions (p = 0.001).

CONCLUSIONS

Sleep in preterm infants might be a key factor in early developmental functioning processes and nervous system integrity. Even in the first months of life, there are substantial differences in cognitive, language, and motor development in association with sleep characteristics.

Contributions of the light environment and co-sleeping to sleep consolidation into nighttime in early infants: A pilot study

BACKGROUND

Sleep consolidation into nighttime is considered the primary goal of sleep development in early infants. However, factors contributing to sleep consolidation into nighttime remain unclear.

AIM

To clarify the influences of the light environment and nighttime co-sleeping on sleep consolidation into nighttime in early infants.

STUDY DESIGN

Cross-sectional study.

SUBJECTS AND METHODS

Sleep-wake time and light stimulation were measured in infants for 4 consecutive days using actigraphy. The infants' mothers were asked to complete a sleep events diary and a questionnaire about childcare, including "co-sleeping", defined as when the infant and mother slept on the same surface throughout the night.

OUTCOME MEASURES

The data were analyzed with a focus on daytime and nighttime sleep parameters.

RESULTS

Daytime light stimulation reduced daytime "active sleep", tended to reduce daytime sleep, and increased daytime waking. Nighttime light stimulation reduced nighttime "quiet sleep" and nighttime sleep and increased nighttime waking. Co-sleeping reduced nighttime waking, and, as a result, nighttime sleep time and sleep efficiency increased. Co-sleeping reduced daytime sleep and tended to increase daytime waking. Consequently, co-sleeping tended to increase the ratio of nighttime sleep to daytime sleep.

CONCLUSIONS

The present findings suggest that an appropriate light environment promotes daytime waking and nighttime sleep in early infants, but it does not contribute to sleep consolidation into nighttime by itself. On the other hand, co-sleeping may promote sleep consolidation into nighttime. Therefore, further methods for safe co-sleeping need to be established while avoiding risk factors for sudden unexpected death in infancy/sudden infant death syndrome.

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.

Microglial Regulation of Sleep and Wakefulness

Sleep serves a multitude of roles in brain maturation and function. Although the neural networks involved in sleep regulation have been extensively characterized, it is increasingly recognized that neurons are not the sole conductor orchestrating the rhythmic cycle of sleep and wakefulness. In the central nervous system, microglia have emerged as an important player in sleep regulation. Within the last two decades, microglia have gained substantial attention for carrying out numerous nonimmune tasks that are crucial for brain development and function by co-opting similar mechanisms used in their conventional immune functions. Here, we highlight the importance of microglia in sleep regulation with recent findings reporting an arrhythmic sleep/wake cycle in the absence of microglia. Although the underlying mechanisms for such regulation are still being uncovered, it is likely that microglial contributions to the rhythmic control of the sleep/wake cycle come from their influence on synaptic strength and neuronal activity. We review the current literature to provide speculative signaling pathways and suggest key questions for future research. Advancing our knowledge of the mechanistic contribution of microglia to sleep regulation will not only further our insight into this critical biological process but also be instrumental in providing novel therapeutic strategies for sleep disorders.

Continuity and change in neural plasticity through embryonic morphogenesis, fetal activity-dependent synaptogenesis, and infant memory consolidation

There is an apparent continuity in human neural development that can be traced to venerable themes of vertebrate morphogenesis that have shaped the evolution of the reptilian telencephalon (including both primitive three-layered cortex and basal ganglia) and then the subsequent evolution of the mammalian six-layered neocortex. In this theoretical analysis, we propose that an evolutionary-developmental analysis of these general morphogenetic themes can help to explain the embryonic development of the dual divisions of the limbic system that control the dorsal and ventral networks of the human neocortex. These include the archicortical (dorsal limbic) Papez circuits regulated by the hippocampus that organize spatial, contextual memory, as well as the paleocortical (ventral limbic) circuits that organize object memory. We review evidence that these dorsal and ventral limbic divisions are controlled by the differential actions of brainstem lemnothalamic and midbrain collothalamic arousal control systems, respectively, thereby traversing the vertebrate subcortical neuraxis. These dual control systems are first seen shaping the phyletic morphogenesis of the archicortical and paleocortical foundations of the forebrain in embryogenesis. They then provide dual modes of activity-dependent synaptic organization in the active (lemnothalamic) and quiet (collothalamic) stages of fetal sleep. Finally, these regulatory systems mature to form the major systems of memory consolidation of postnatal development, including the rapid eye movement (lemnothalamic) consolidation of implicit memory and social attachment in the first year, and then-in a subsequent stage-the non-REM (collothalamic) consolidation of explicit memory that is integral to the autonomy and individuation of the second year of life.

Evaluation of Sleep Practices and Knowledge in Neonatal Healthcare

BACKGROUND

Developmental care is designed to optimize early brain maturation by integrating procedures that support a healing environment. Protecting preterm sleep is important in developmental care. However, it is unclear to what extent healthcare professionals are aware of the importance of sleep and how sleep is currently implemented in the day-to-day care in the neonatal intensive care unit (NICU).

PURPOSE

Identifying the current state of knowledge among healthcare professionals regarding neonatal sleep and how this is transferred to practice.

METHODS

A survey was distributed among Dutch healthcare professionals. Three categories of data were sought, including (1) demographics of respondents; (2) questions relating to sleep practices; and (3) objective knowledge questions relating to sleep physiology and importance of sleep. Data were analyzed using Spearman's rho test and Cramer's V test. Furthermore, frequency tables and qualitative analyses were employed.

RESULTS

The survey was completed by 427 participants from 34 hospitals in 25 Dutch cities. While healthcare professionals reported sleep to be especially important for neonates admitted in the NICU, low scores were achieved in the area of knowledge of sleep physiology. Most healthcare professionals (91.8%) adapted the timing of elective care procedures to sleep. However, sleep assessments were not based on scientific knowledge. Therefore, the difference between active sleep and wakefulness may often be wrongly assessed. Finally, sleep is rarely discussed between colleagues (27.4% regularly/always) and during rounds (7.5%-14.3% often/always).

IMPLICATIONS

Knowledge about sleep physiology should be increased through education among neonatal healthcare professionals. Furthermore, sleep should be considered more often during rounds and handovers.

Antiplatelet Effect of Melatonin through Breastfeeding: A Pediatric Case Report

We present a pediatric case of the antiplatelet effect of melatonin taken through breast milk in an 18-month-old child. The child was referred to our hematology outpatient clinic because of bleeding episodes that she presented since birth. Blood tests excluded the presence of blood coagulation diseases. The family history was negative for bleeding disorders. The child did not consume any drugs, food supplements, herbal teas or infusions. We performed an aggregation platelet test, which showed a reduced platelet aggregation. Shortly before, the baby had been breastfed. We speculated that breast milk could interfere with the result of the test; therefore, we decided to repeat the test in a fasting state. This time the test showed a normal platelet aggregation time. We learned that the child's mother was taking a mixture of valerian and melatonin. Thus, we decided to suspend maternal intake of melatonin and perform a new platelet aggregation test after three months. The test results were negative. After the suspension of melatonin, the patient did not present further bleeding events. In this case, melatonin, through the inhibition of platelet aggregation, had an important role on the hemostatic system of the child. Melatonin is considered as a dietary supplement and is mostly available as an alternative medicine without formal prescription and dosage regulation. It is important, especially during breastfeeding, to investigate personal and medication history, including also homeopathic remedies or dietary supplements.

Language Exposure for Preterm Infants is Reduced Relative to Fetuses

OBJECTIVE

To assess changes and deficits in language and auditory exposures consequent to preterm birth and neonatal intensive care unit stay compared with exposures in utero among typically developing fetuses.

STUDY DESIGN

We analyzed over 23 000 hours of auditory exposure data in a cohort study of 27 typically-developing fetuses and 24 preterm infants. Extrauterine exposures for fetuses were captured by having pregnant women wear 24-hour audio recording devices. For preterm infants, recording devices were placed in the infant's crib. Multilevel linear regressions were conducted to test for group differences and effects of infant sex, maternal education, and mother' occupation. A linear mixed-effects model was used to test for an effect of speaker gender.

RESULTS

Fetuses were exposed to an estimated 2.6 ± 1.8 hours/day of nearby, predominantly female language, nearly 5 times greater than 32 ± 12 minutes/day estimated for preterm infants (P < .001). Preterm infants had greater daily exposure to electronic sounds (5.1 ± 2.5 vs 1.3 ± 0.6 hours; P < .001) and noise (4.4 ± 2.1 vs 2.9 ± 2.8 hours; P < .05), with 4.7 ± 3.9 hours/day of silence. Language and extrauterine sound exposure for fetuses showed a marked day/night cyclical pattern, with low exposure during nighttime hours, but preterm infants' exposures showed significantly less change across the 24-hour cycle (P < .001). Maternal occupation requiring frequent communication predicted greater language exposure (P < .05).

CONCLUSIONS

Our findings provide the first comparison of preterm infant auditory exposures to typically-developing fetuses. Some preterm infants may incur deficits of over 150 hours of language exposure over the preterm period. Given known effects of prenatal/preterm language exposure on neurobehavioral outcomes, this magnitude of deficit is alarming.

Sleep disturbances are associated with feeding practices and age in preterm infants

BACKGROUND

Preterm infants are under risk of several shortcomings including sleep disturbances (SD). This cross-sectional study evaluated factors associated with SD in preterm and low birth weight infants in a reference center for preterm children at a University Hospital, southeastern Brazil.

METHODS

A hundred-four dyads of mothers-infants 0-3 years participated. Mothers answered an online questionnaire (Google Forms®) evaluating childbirth characteristics, gestational age, breastfeeding, bottle feeding, non-nutritive sucking habits and sociodemographic information. The Brazilian version of the Brief Infant Sleep Questionnaire (BISQ) evaluated SD. Bivariate and Logistic Regression analyses were performed (p < 0.05).

RESULTS

SD was present in 45.2% of the sample. Multivariate Logistic Regression Model showed that infants breastfed ≥3 times at night had 5.006 more chances to have SD (CI 95% = 1.229-20.400) compared to those who did not breastfeed at night. Infants who were bottle-fed 3 ≥ times at night had 6.952 more chances to have SD (CI = 95% = 1.364-35.427) compared to those who were bottle fed less frequently. The chance of SD decreased 6.6% (CI 95% = 0.889-0.982) for each increase of a month in infant's age, and infants from families with higher income had 3.535 more chances to have SD (CI 95% = 1.006-12.416).

CONCLUSION

The younger the child, a higher frequency of night feeding and belonging to higher income families were associated with SD. Recognizing the associated factors with SD in newborns and infants can aid families to better deal with this issue, promote better sleep quality and individualized counseling.

To Trach or Not To Trach: Long-term Tracheostomy Outcomes in Infants with BPD

See Bonus NeoBriefs videos and downloadable teaching slides Infants born preterm who are diagnosed with bronchopulmonary dysplasia (BPD) demonstrate a wide spectrum of illness severity. For infants with the most severe forms of BPD, safe discharge from the hospital may only be possible by providing long-term ventilation via a surgically placed tracheostomy. Though tracheostomy placement in infants with BPD is infrequent, recent reports suggest that rates of tracheostomy placement are increasing in this population. Even though there are known respiratory and neurodevelopmental risks associated with tracheostomy placement, no evidence-based criteria or consensus clinical practice guidelines exist to inform tracheostomy placement in this growing and vulnerable population. An incomplete knowledge of long-term post-tracheostomy outcomes in infants with BPD may unduly bias medical decision-making and family counseling regarding tracheostomy placement. This review aims to summarize our current knowledge of the epidemiology and long-term outcomes of tracheostomy placement in infants with BPD to provide a family-centered framework for tracheostomy counseling.

Not simply a matter of parents-Infants' sleep-wake patterns are associated with their regularity of eating

In adults there are indications that regular eating patterns are related to better sleep quality. During early development, sleep and eating habits experience major maturational transitions. Further, the bacterial landscape of the gut microbiota undergoes a rapid increase in complexity. Yet little is known about the association between sleep, eating patterns and the gut microbiota. We first hypothesized that higher eating regularity is associated with more mature sleep patterns, and second, that this association is mediated by the maturational status of the gut microbiota. To test this hypothesis, we performed a longitudinal study in 162 infants to assess actigraphy, diaries of sleep and eating times, and stool microbiota composition at ages 3, 6 and 12 months. To comprehensively capture infants' habitual sleep-wake patterns, 5 sleep composites that characterize infants' sleep habits across multiple days in their home environment were computed. To assess timing of eating habits, we developed an Eating Regularity Index (ERI). Gut microbial composition was assessed by 16S rRNA gene amplicon sequencing, and its maturation was assessed based on alpha diversity, bacterial maturation index, and enterotype. First, our results demonstrate that increased eating regularity (higher ERI) in infants is associated with less time spent awake during the night (sleep fragmentation) and more regular sleep patterns. Second, the associations of ERI with sleep evolve with age. Third, the link between infant sleep and ERI remains significant when controlling for parents' subjectively rated importance of structuring their infant's eating and sleeping times. Finally, the gut microbial maturational markers did not account for the link between infant's sleep patterns and ERI. Thus, infants who eat more regularly have more mature sleep patterns, which is independent of the maturational status of their gut microbiota. Interventions targeting infant eating rhythm thus constitute a simple, ready-to-use anchor to improve sleep quality.

The Ponto-Geniculo-Occipital (PGO) Waves in Dreaming: An Overview

Rapid eye movement (REM) sleep is the main sleep correlate of dreaming. Ponto-geniculo-occipital (PGO) waves are a signature of REM sleep. They represent the physiological mechanism of REM sleep that specifically limits the processing of external information. PGO waves look just like a message sent from the pons to the lateral geniculate nucleus of the visual thalamus, the occipital cortex, and other areas of the brain. The dedicated visual pathway of PGO waves can be interpreted by the brain as visual information, leading to the visual hallucinosis of dreams. PGO waves are considered to be both a reflection of REM sleep brain activity and causal to dreams due to their stimulation of the cortex. In this review, we summarize the role of PGO waves in potential neural circuits of two major theories, i.e., (1) dreams are generated by the activation of neural activity in the brainstem; (2) PGO waves signaling to the cortex. In addition, the potential physiological functions during REM sleep dreams, such as memory consolidation, unlearning, and brain development and plasticity and mood regulation, are discussed. It is hoped that our review will support and encourage research into the phenomenon of human PGO waves and their possible functions in dreaming.

Developmental emergence of sleep rhythms enables long-term memory in Drosophila

In adulthood, sleep-wake rhythms are one of the most prominent behaviors under circadian control. However, during early life, sleep is spread across the 24-hour day. The mechanism through which sleep rhythms emerge, and consequent advantage conferred to a juvenile animal, is unknown. In the second-instar Drosophila larvae (L2), like in human infants, sleep is not under circadian control. We identify the precise developmental time point when the clock begins to regulate sleep in Drosophila, leading to emergence of sleep rhythms in early third-instars (L3). At this stage, a cellular connection forms between DN1a clock neurons and arousal-promoting Dh44 neurons, bringing arousal under clock control to drive emergence of circadian sleep. Last, we demonstrate that L3 but not L2 larvae exhibit long-term memory (LTM) of aversive cues and that this LTM depends upon deep sleep generated once sleep rhythms begin. We propose that the developmental emergence of circadian sleep enables more complex cognitive processes, including the onset of enduring memories.

Fetal SSRI antidepressant exposure and infant sleep: Findings from the MPEWS pregnancy cohort study

This longitudinal study examines the association between fetal Selective Serotonergic Reuptake Inhibitor antidepressant exposure and infant sleep behaviours at six and 12 months of age and focus on three of the most commonly prescribed antidepressants in pregnancy. This study utilises data on 698 women recruited at less than 20 weeks of pregnancy and are followed up at six and 12 months postpartum. Women were recruited into one of three groups: those taking either sertraline, citalopram or escitalopram antidepressants in pregnancy (n = 85); women with a depressive disorder who were not taking antidepressants (non-medicated depressed, NMD; n = 82); and, and a control group of women (n = 531). At six and 12 months, data were collected on breastfeeding and sleep location and infant sleep was measured using the Brief Infant Sleep Questionnaire. Antidepressants sertraline, escitalopram and citalopram were not associated with increased infant waking or time awake. However, sertraline was associated with longer time for an infant to go to sleep. This study provides reassurance that SSRI antidepressants and, in particular, sertraline, escitalopram and citalopram are not associated with infant sleep behaviours that are commonly regarded as problematic including night waking. Further replication of these findings, including with direct measures of infant sleep, are recommended.

Pediatric sleep: current knowledge, gaps, and opportunities for the future

This White Paper addresses the current gaps in knowledge, as well as opportunities for future studies in pediatric sleep. The Sleep Research Society's Pipeline Development Committee assembled a panel of experts tasked to provide information to those interested in learning more about the field of pediatric sleep, including trainees. We cover the scope of pediatric sleep, including epidemiological studies and the development of sleep and circadian rhythms in early childhood and adolescence. Additionally, we discuss current knowledge of insufficient sleep and circadian disruption, addressing the neuropsychological impact (affective functioning) and cardiometabolic consequences. A significant portion of this White Paper explores pediatric sleep disorders (including circadian rhythm disorders, insomnia, restless leg and periodic limb movement disorder, narcolepsy, and sleep apnea), as well as sleep and neurodevelopment disorders (e.g. autism and attention deficit hyperactivity disorder). Finally, we end with a discussion on sleep and public health policy. Although we have made strides in our knowledge of pediatric sleep, it is imperative that we address the gaps to the best of our knowledge and the pitfalls of our methodologies. For example, more work needs to be done to assess pediatric sleep using objective methodologies (i.e. actigraphy and polysomnography), to explore sleep disparities, to improve accessibility to evidence-based treatments, and to identify potential risks and protective markers of disorders in children. Expanding trainee exposure to pediatric sleep and elucidating future directions for study will significantly improve the future of the field.

Sensory processing and sleep characteristics in preterm infants in the early period of life

OBJECTIVE

The present study aimed to investigate the following: (i) differences in sensory processing and sleep characteristics between preterm infants born at < 32 weeks', vs. those born at ≥ 32 weeks' gestation; (ii) differences in sleep characteristics between preterm infants with typical vs. atypical sensory processing; and (iii) relationship between sensory processing and sleep characteristics in preterm infants at 3 months of age.

METHODS

A total of 189 preterm infants, 54 born at < 32 weeks' gestation (26 females; mean gestational age [standard deviation (SD)], 30.1 [1.7] weeks), and 135 born at ≥ 32 weeks' gestation (78 females; mean gestational age [SD], 34.9 [0.9] weeks) were included in the present study. Sleep characteristics were evaluated using the Brief Infant Sleep Questionnaire, and sensory processing was assessed using the Infant Sensory Profile-2.

RESULTS

There were no significant differences in sensory processing (P > 0.05) or sleep characteristics (P > 0.05) between the preterm groups; however, more infants snored in the <32 weeks' gestation group (P = 0.035). Preterm infants with atypical sensory processing showed lower nighttime (P = 0.027) and total sleep durations (P = 0.032), and higher rates of nocturnal wakefulness (P = 0.038) and snoring (P = 0.001) than preterm infants with typical sensory processing. A significant relationship, therefore, was observed between sensory processing and sleep characteristics (P < 0.05).

CONCLUSIONS

Sensory processing patterns may play an important role in understanding sleep problems in preterm infants. The early detection of sleep problems and sensory processing difficulties are necessary for early intervention.

Mammalian NREM and REM sleep: Why, when and how

This report proposes that fish use the spinal-rhombencephalic regions of their brain to support their activities while awake. Instead, the brainstem-diencephalic regions support the wakefulness in amphibians and reptiles. Lastly, mammals developed the telencephalic cortex to attain the highest degree of wakefulness, the cortical wakefulness. However, a paralyzed form of spinal-rhombencephalic wakefulness remains in mammals in the form of REMS, whose phasic signs are highly efficient in promoting maternal care to mammalian litter. Therefore, the phasic REMS is highly adaptive. However, their importance is low for singletons, in which it is a neutral trait, devoid of adaptive value for adults, and is mal-adaptive for marine mammals. Therefore, they lost it. The spinal-rhombencephalic and cortical wakeful states disregard the homeostasis: animals only attend their most immediate needs: foraging defense and reproduction. However, these activities generate allostatic loads that must be recovered during NREMS, that is a paralyzed form of the amphibian-reptilian subcortical wakefulness. Regarding the regulation of tonic REMS, it depends on a hypothalamic switch. Instead, the phasic REMS depends on an independent proportional pontine control.

Sleep from Infancy Through Adolescence

This article describes the changes in normal sleep regulation, structure, and organization and sleep-related changes in respiration from infancy to adolescence. The first 2 years of age are striking, with more time asleep than awake. With development, the electroencephalogram architecture has a marked reduction in rapid eye movement sleep and the acquisition of K-complexes, sleep spindles, and slow-wave sleep. During adolescence there is a reduction in slow-wave sleep and a delay in the circadian phase. Infants have a more collapsible upper airway and lower lung volumes than older children, which predisposes them to obstructive sleep apnea and sleep-related hypoxemia.

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.

Sleep patterns in childhood: a longitudinal assessment from the Generation XXI birth cohort

OBJECTIVE

To describe sleep-wake patterns in young children, based on sleep characteristics in early infancy and preschool ages, identifying their main sociodemographic characteristics, and to assess the association between different sleep characteristics at both ages.

METHOD

We included 1092 children from the Generation XXI birth cohort, evaluated at six months and four years of age, by face-to-face interviews. Sleep patterns were constructed through latent class analysis and structured equation modeling, including data on wake-up time and bedtime, afternoon naps, locale of nighttime sleep and night awakenings. To estimate the association between sociodemographic characteristics and sleep patterns, odds ratios and 95% confidence intervals were computed using logistic regression.

RESULTS

Two sleep patterns were identified through latent class analysis: pattern 1 was characterized by earlier bedtime and wake-up times, while pattern 2 was defined by later times. When compared with pattern 1, pattern 2 was more frequent among children whose mothers had changed from partnered to not partnered until preschool age and those who did not stay at the kindergarten, and was less common among those with siblings. Through structured equation modeling, an aggregating factor was identified at preschool age, which was mainly correlated with bedtime and wake-up time. A positive association between sleep characteristics evaluated in early infancy and in preschool ages was observed.

CONCLUSIONS

Sleep patterns and circadian sleep preferences seem to be developed early in life, which highlight the importance of promoting an adequate sleep hygiene from infancy, assuming its impact on sleep quality during the life course.

Cot-side imaging of functional connectivity in the developing brain during sleep using wearable high-density diffuse optical tomography

Studies of cortical function in newborn infants in clinical settings are extremely challenging to undertake with traditional neuroimaging approaches. Partly in response to this challenge, functional near-infrared spectroscopy (fNIRS) has become an increasingly common clinical research tool but has significant limitations including a low spatial resolution and poor depth specificity. Moreover, the bulky optical fibres required in traditional fNIRS approaches present significant mechanical challenges, particularly for the study of vulnerable newborn infants. A new generation of wearable, modular, high-density diffuse optical tomography (HD-DOT) technologies has recently emerged that overcomes many of the limitations of traditional, fibre-based and low-density fNIRS measurements. Driven by the development of this new technology, we have undertaken the first cot-side study of newborn infants using wearable HD-DOT in a clinical setting. We use this technology to study functional brain connectivity (FC) in newborn infants during sleep and assess the effect of neonatal sleep states, active sleep (AS) and quiet sleep (QS), on resting state FC. Our results demonstrate that it is now possible to obtain high-quality functional images of the neonatal brain in the clinical setting with few constraints. Our results also suggest that sleep states differentially affect FC in the neonatal brain, consistent with prior reports.

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.

Sleep State Trend (SST), a bedside measure of neonatal sleep state fluctuations based on single EEG channels

OBJECTIVE

To develop and validate an automated method for bedside monitoring of sleep state fluctuations in neonatal intensive care units.

METHODS

A deep learning-based algorithm was designed and trained using 53 EEG recordings from a long-term (a)EEG monitoring in 30 near-term neonates. The results were validated using an independent dataset from 30 polysomnography recordings. In addition, we constructed Sleep State Trend (SST), a bedside-ready means for visualizing classifier outputs.

RESULTS

The accuracy of quiet sleep detection in the training data was 90%, and the accuracy was comparable (85-86 %) in all bipolar derivations available from the 4-electrode recordings. The algorithm generalized well to a polysomnography dataset, showing 81% overall accuracy despite different signal derivations. SST allowed an intuitive, clear visualization of the classifier output.

CONCLUSIONS

Fluctuations in sleep states can be detected at high fidelity from a single EEG channel, and the results can be visualized as a transparent and intuitive trend in the bedside monitors.

SIGNIFICANCE

The Sleep State Trend (SST) may provide caregivers and clinical studies a real-time view of sleep state fluctuations and its cyclicity.

Sleep architecture in neonatal and infantile onset epilepsies in the first six months of life: A scoping review

AIM

Epilepsy occurs in approximately 80 per 100,000 infants in the first year of life, ranging in severity from self-limited and likely to spontaneously resolve, to severe developmental and epileptic encephalopathies. Sleep plays a key role in early brain development and the reciprocal relationship between sleep and seizures is not yet fully understood, particularly in young children. We conducted a Scoping Review to synthesise current knowledge of sleep architecture in neonates and infants with epilepsy.

METHOD

Peer-reviewed publications from 2005 to 2022 describing sleep architecture in infants up to six months of age with unprovoked seizures were included. The analysis set was derived from EMBASE, Web of Science and PubMED using key terms "sleep, epilepsy and infant" and related descriptors. Inclusion criteria were prospectively described in a Scoping Review protocol. Sleep architecture was assessed as macro- and micro-structural elements.

RESULTS

21 publications were included in the qualitative analysis. In self-limited familial and genetic epilepsy, sleep macrostructure was generally preserved. In DEEs and in epileptic encephalopathies of genetic or structural aetiology, sleep architecture was significantly disrupted.

INTERPRETATION

Early identification of infants with epilepsy is important to ensure early and effective treatment. In the DEE spectrum, sleep architecture is significantly impacted, and abnormal sleep architecture may be associated with compromised developmental outcome. Further research is needed to identify the sequence of events in abnormal brain development, epilepsy and sleep disruption and potentially help to predict the course of epilepsy towards a self-limited epilepsy versus a DEE.

Brain Metabolic DNA: A Long Story and Some Conclusions

We have previously outlined the main properties of brain metabolic DNA (BMD) and its involvement in circadian oscillations, learning, and post-trial sleep. The presence of BMD in certain subcellular fractions and their behavior in cesium gradients have suggested that BMD originates from cytoplasmic reverse transcription and subsequently acquires a double-stranded configuration. More recently, it has been reported that some DNA sequences of cytoplasmic BMD in learning mice are different from that of the control animals. Furthermore, BMD is located in vicinity of the genes involved in different modifications of synaptic activity, suggesting that BMD may contribute to the brain's response to the changing environment. The present review outlines recent data with a special emphasis on reverse transcription of BMD that may recapitulate the molecular events at the time of the "RNA world" by activating mitochondrial telomerase and generating RNA templates from mitochondrial transcripts. The latter unexpected role of mitochondria is likely to promote a better understanding of mitochondrial contribution to cellular interactions and eukaryotic evolution. An initial step regards the role of human mitochondria in embryonic BMD synthesis, which is exclusively of maternal origin. In addition, mitochondrial transcripts involved in reverse transcription of BMD might possibly reveal unexpected features elucidating mitochondrial involvement in cancer events and neurodegenerative disorders.

Rapid Eye Movement Sleep during Early Life: A Comprehensive Narrative Review

The ontogenetic sleep hypothesis suggested that rapid eye movement (REM) sleep is ontogenetically primitive. Namely, REM sleep plays an imperative role in the maturation of the central nervous system. In coincidence with a rapidly developing brain during the early period of life, a remarkably large amount of REM sleep has been identified in numerous behavioral and polysomnographic studies across species. The abundant REM sleep appears to serve to optimize a cerebral state suitable for homeostasis and inherent neuronal activities favorable to brain maturation, ranging from neuronal differentiation, migration, and myelination to synaptic formation and elimination. Progressively more studies in Mammalia have provided the underlying mechanisms involved in some REM sleep-related disorders (e.g., narcolepsy, autism, attention deficit hyperactivity disorder (ADHD)). We summarize the remarkable alterations of polysomnographic, behavioral, and physiological characteristics in humans and Mammalia. Through a comprehensive review, we offer a hybrid of animal and human findings, demonstrating that early-life REM sleep disturbances constitute a common feature of many neurodevelopmental disorders. Our review may assist and promote investigations of the underlying mechanisms, functions, and neurodevelopmental diseases involved in REM sleep during early life.

Preliminary Exploration into the Impact of Mistimed Expressed Breast Milk Feeding on Infant Sleep Outcomes, Compared to Other Feeding Patterns

Background and Objective: The presence and fluctuation of melatonin in breast milk during the night and day may be providing sleep timing information to infants, thereby supporting/enabling the development of their own circadian cycle. If this is the case, then it is important that infants consume breast milk according to the time of day it is produced. However, breast milk is not always consumed at the "right" time. The aim of this study was to investigate whether consuming mistimed expressed breast milk impacts infant sleep compared with other feeding types. Methods: A total of 329 mothers completed an online anonymous survey. Mothers were grouped into one of five groups; direct breastfed only, formula only, express mistimed, express-timed, and combined breastfed/formula fed. Results: Cross-sectional analysis showed mistimed expressed breast milk was significantly associated with delayed sleep onset of the infant (p < 0.001), but direct breastfed infants had significantly more awakenings at night (p < 0.001). Conclusions: The findings from this study suggest a potential effect of mistimed expressed breast milk consumption on an infant's circadian rhythm, affecting some aspects of their sleep. This is an important first step in exploring mistimed feeding on infant sleep outcomes and provides preliminary evidence that warrants future research.

The contribution of whole-exome sequencing to intellectual disability diagnosis and knowledge of underlying molecular mechanisms: A systematic review and meta-analysis

Whole-exome sequencing (WES) is useful for molecular diagnosis, family genetic counseling, and prognosis of intellectual disability (ID). However, ID molecular diagnosis ascertainment based on WES is highly dependent on de novo mutations (DNMs) and variants of uncertain significance (VUS). The quantification of DNM frequency in ID molecular diagnosis ascertainment and the biological mechanisms common to genes with VUS may provide objective information about WES use in ID diagnosis and etiology. We aimed to investigate and estimate the rate of ID molecular diagnostic assessment by WES, quantify the contribution of DNMs to this rate, and biologically and functionally characterize the genes whose mutations were identified through WES. A PubMed/Medline, Web of Science, Scopus, Science Direct, BIREME, and PsycINFO systematic review and meta-analysis was performed, including studies published between 2010 and 2022. Thirty-seven articles with data on ID molecular diagnostic yield using the WES approach were included in the review. WES testing accounted for an overall diagnostic rate of 42% (Confidence interval (CI): 35-50%), while the estimate restricted to DNMs was 11% (CI: 6-18%). Genetic information on mutations and genes was extracted and split into two groups: (1) genes whose mutation was used for positive molecular diagnosis, and (2) genes whose mutation led to uncertain molecular diagnosis. After functional enrichment analysis, in addition to their expected roles in neurodevelopment, genes from the first group were enriched in epigenetic regulatory mechanisms, immune system regulation, and circadian rhythm control. Genes from uncertain diagnosis cases were enriched in the renin angiotensin pathway. Taken together, our results support WES as an important approach to the molecular diagnosis of ID. The results also indicated relevant pathways that may underlie the pathogenesis of ID with the renin-angiotensin pathway being suggested to be a potential pathway underlying the pathogenesis of ID.

Development of circadian rest-activity rhythms during the first year of life in a racially diverse cohort

STUDY OBJECTIVES

To describe the development of circadian rest-activity rhythms (CRARs) during infancy in a racially diverse cohort.

METHODS

We studied 414 infants from the Nurture birth cohort (51.2% female, 65.2% Black) who wore actigraphs on their left ankles for 4 days and nights at 3, 6, 9, and 12 months. We quantified CRARs using cosinor and non-parametric circadian rhythm analysis, and investigated change in CRARs over time, comparing 6, 9, and 12 months to CRARs at 3 months. We adjusted for baseline and time-varying covariates and used function-on-scalar regression (FOSR) to identify the specific times of day at which activity changes occurred.

RESULTS

Across the first year, daily mean and peak activity levels and day-to-day activity level regularity increased, and activity level fragmentation and nighttime activity decreased. Only at 9 months, compared to at 3 months, did timing of peak activity levels and the most active periods shift later, while timing of least active periods shifted earlier. FOSR analyses showed that mean activity levels decreased during nighttime hours and increased during daytime hours, with the most pronounced changes at 9 months.

CONCLUSIONS

Among racially diverse infants, CRARs became more robust, stable, and less fragmented over time. Findings suggest the greatest change from 3-month CRARs occurs at 9 months, which may be a key period of CRAR development. This and future research will contribute to our understanding of normative infant CRAR development in diverse populations and enable us to identify infants who may benefit from intervention.

What Are the Factors Affecting Total Sleep Time During Video Polysomnography in Infants?

OBJECTIVE

The aim of the study is to investigate factors affecting total sleep time (TST) during infant polysomnography (PSG) and assess if <4 hours of TST is sufficient for accurate interpretation.

STUDY DESIGN

Overall, 242 PSGs performed in 194 infants <6 months of chronological age between March 2013 and December 2015 were reviewed to identify factors that affect TST, including age of infant, location and timing of study, presence of medical complexity, and presence of nasal tubes. A continuum of apnea-hypopnea index (AHI) in relation to TST was reviewed. Data were examined in infants who had TST <4 hours and low AHI.

RESULTS

Greater TST (p < 0.001) was noted among infants during nocturnal PSGs, at older chronological and post-menstrual ages, and without medical complexity. The presence of nasogastric/impedance probes reduced TST (p = 0.002). Elevated AHIs were identified even in PSGs with TST <4 hours. Short TST may have affected interpretation and delayed initial management in one infant without any inadvertent complications.

CONCLUSION

Clinical factors such as PMA and medical complexity, and potentially modifiable factors such as time of day and location of study appeared to affect TST during infant PSGs. TST < 4 hours can be sufficient to identify high AHI allowing physician interpretation.

KEY POINTS

· Less than 4 hours of TST is enough for interpretation of infant polysomnography.. · Shorter TST appears related to infant age, medical complexity, and higher apnea-hypopnea index.. · Modifiable factors seen with higher TST were time of day, environment, and presence of nasal tubes..

Use of Child Care Attenuates the Link Between Decreased Maternal Sleep and Increased Depressive Symptoms

OBJECTIVE

Sleep disruption is common among postpartum women and is linked with depression. Child care may alleviate parenting stress and protect new mothers against symptoms of depression.

METHODS

Mothers from the NURTURE study, a birth cohort of 666 women of full-term infants, completed questionnaires during home visits when their infants were 3, 6, 9, and 12 months old. The Edinburgh Postnatal Depression Scale and the Perceived Stress Scale were used to measure depressive symptoms and stress, respectively. Mothers reported total nightly sleep duration for themselves and their infants, child care arrangements, marital status, and income. We used mixed-effects models adjusting for income, marital status, and child age to examine the indirect effect of infants' sleep on maternal mental health through mothers' sleep and assessed whether patterns differed depending on child care.

RESULTS

Decreased maternal sleep mediated the association between infant sleep and maternal mental health. When infants slept 1 hour less than usual, mothers slept 7 fewer minutes (B = 0.19, 95% confidence interval [CI], 0.01 to 0.27) and reported more depressive symptoms (B = -0.27, 95% CI, -0.43 to -0.11) and stress (B = -0.33, 95% CI -0.58 to -0.09). Child care moderated the indirect effect; decreased maternal sleep was not associated with increased depressive symptoms (and was not a mediator) when mothers had child care (indirect effect = -0.001, 95% CI, -0.03 to 0.03).

CONCLUSION

Use of infant child care reduced the link between maternal sleep and depressive symptoms. Regular access to child care may be a method to mitigate feelings of depression for new mothers.

Association of fetal eye movement density with sleeping and developmental problems in 1.5-year-old infants

Eye movement density (EMD) is an evaluation index of rapid eye movements observed during sleep. This study aimed to investigate the association of fetal EMD with sleeping and developmental problems in infancy. We observed 60 normal singleton pregnancies (gestational age 28-37 weeks) using ultrasonography for 1 h. Fetal eye movements were counted, and EMD was calculated. Participants answered questionnaires regarding their child's sleep and development 1.5 years after their delivery. The outcomes of an infant's sleep were night awakening (yes or no), bedtime (before or after 22:00), and nighttime sleep duration (< 9 or ≥ 9 h). An infant's development was evaluated using the Child Behavior Checklist (CBCL) T-score. We found that decreased fetal EMD was associated with increased night awakening at the age of 1.5 years (odds ratio 0.84, 95% confidence interval 0.69-1.00 per unit decrease in EMD). However, fetal EMD was not associated with bedtime or nighttime sleep duration. In addition, fetal EMD was independently associated with the total problems T-score of the CBCL at the age of 1.5 years in the multivariate model (p = 0.047). In conclusion, fetal EMD may be associated with sleep and developmental problems in infants.

Breast Milk and the Importance of Chrononutrition

During pregnancy the human fetus receives timed cues from the circadian rhythms of temperature, metabolites, and hormones from the mother. This influence is interrupted after parturition, the infant does not secrete melatonin and their circadian rhythms are still immature. However, evolution provided the solution to this problem. The newborn can continue receiving the mother's timed cues through breastmilk. Colostrum, transitional, and mature human milk are extraordinary complex biofluids that besides nutrients, contain an array of other non-nutritive components. Upon birth the first milk, colostrum, is rich in bioactive, immunological factors, and in complex oligosaccharides which help the proper establishment of the microbiome in the gut, which is crucial for the infants' health. Hormones, such as glucocorticoids and melatonin, transfer from the mother's plasma to milk, and then the infant is exposed to circadian cues from their mother. Also, milk components of fat, proteins, amino acids, and endogenous cannabinoids, among others, have a markedly different concentration between day and night. In the present review, we give an overview of nutritive and non-nutritive components and their daily rhythms in human milk and explore their physiological importance for the infant. Finally, we highlight some interventions with a circadian approach that emphasize the importance of circadian rhythms in the newborn for their survival, proper growth, and development. It is estimated that ~600,000 deaths/year are due to suboptimal breastfeeding. It is advisable to increase the rate of exclusive breastfeeding, during the day and night, as was established by the evolution of our species.

The history of sleep research and sleep medicine in Europe

Sleep became a subject of scientific research in the second half of the 19th century. Since sleep, unlike other physiological functions, cannot be attributed to a specific organ, there was no distinct method available to study sleep until then. With the development of physiology and psychology, and a rapidly increasing knowledge of the structure and functioning of the nervous system, certain aspects of sleep became accessible to objective study. A first step was to measure responsiveness to external stimuli systematically, during sleep, allowing a first representation of the course of sleep (Schlaftiefe = sleep depth). A second method was to register continuously the motor activity across the sleep-wake cycle, which allowed the documentation in detail of rest-activity patterns of monophasic and polyphasic sleep-wake rhythms, or between day or night active animals. The central measurement for sleep research, however, became the electroencephalogram in the 1930s, which allowed observation of the sleeping brain with high temporal resolution. Beside the development of instruments to measure sleep, prolonged sleep deprivation was applied to study physiological and psychological effects of sleep loss. Another input came from clinical and neuropathological observations of patients with pronounced disorders of the sleep-wake cycle, which for the first time allowed localisation of brain areas that are essentially involved in the regulation of sleep and wakefulness. Experimental brain stimulation and lesion studies were carried out with the same aim at this time. Many of these activities came to a halt on the eve of World War II. It was only in the early 1950s, when periods with rapid eye movements during sleep were recognised, that sleep became a research topic of itself. Jouvet and his team explored the brain mechanisms and transmitters of paradoxical sleep, and experimental sleep research became established in all European countries. Sleep medicine evolving simultaneously in different countries, with early centres in Italy and France. In the late 1960s sleep research and chronobiology began to merge. In recent decades, sleep research, dream research, and sleep medicine have benefited greatly from new methods in genetic research and brain imaging techniques. Genes were identified that are involved in the regulation of sleep, circadian rhythms, or sleep disorders. Functional imaging enabled a high spatial resolution of the activity of the sleeping brain, complementing the high temporal resolution of the electroencephalogram.

The vision of dreams: from ontogeny to dream engineering in blindness

The mechanisms involved in the origin of dreams remain one of the great unknowns in science. In the 21st century, studies in the field have focused on 3 main topics: functional networks that underlie dreaming, neural correlates of dream contents, and signal propagation. We review neuroscientific studies about dreaming processes, focusing on their cortical correlations. The involvement of frontoparietal regions in the dream-retrieval process allows us to discuss it in light of the Global Workspace theory of consciousness. However, dreaming in distinct sleep stages maintains relevant differences, suggesting that multiple generators are implicated. Then, given the strong influence of light perception on sleep regulation and the mostly visual content of dreams, we investigate the effect of blindness on the organization of dreams. Blind individuals represent a worthwhile population to clarify the role of perceptual systems in dream generation, and to make inferences about their top-down and/or bottom-up origin. Indeed, congenitally blind people maintain the ability to produce visual dreams, suggesting that bottom-up mechanisms could be associated with innate body schemes or multisensory integration processes. Finally, we propose the new dream-engineering technique as a tool to clarify the mechanisms of multisensory integration during sleep and related mental activity, presenting possible implications for rehabilitation in sensory-impaired individuals. The Theory of Proto-consciousness suggests that the interaction of brain states underlying waking and dreaming ensures the optimal functioning of both. Therefore, understanding the origin of dreams and capabilities of our brain during a dreamlike state, we could introduce it as a rehabilitative tool.

CITATION

Vitali H, Campus C, De Giorgis V, Signorini S, Gori M. The vision of dreams: from ontogeny to dream engineering in blindness. J Clin Sleep Med. 2022;18(8):2051-2062.