Which are the Central Aspects of Infant Sleep? The Dynamics of Sleep Composites across Infancy

Bedtime to the brain: how infants' sleep behaviours intertwine with non-rapid eye movement sleep electroencephalography features

Adequate sleep is critical for development and facilitates the maturation of the neurophysiological circuitries at the basis of cognitive and behavioural function. Observational research has associated early life sleep problems with worse later cognitive, psychosocial, and somatic health outcomes. Yet, the extent to which day-to-day sleep behaviours (e.g., duration, regularity) in early life relate to non-rapid eye movement (NREM) neurophysiology-acutely and the long-term-remains to be studied. We measured sleep behaviours in 32 healthy 6-month-olds assessed with actimetry and neurophysiology with high-density electroencephalography (EEG) to investigate the association between NREM sleep and habitual sleep behaviours. Our study revealed four findings: first, daytime sleep behaviours are related to EEG slow-wave activity (SWA). Second, night-time movement and awakenings from sleep are connected with spindle density. Third, habitual sleep timing is linked to neurophysiological connectivity quantified as delta coherence. And lastly, delta coherence at 6 months predicts night-time sleep duration at 12 months. These novel findings widen our understanding that infants' sleep behaviours are closely intertwined with three particular levels of neurophysiology: sleep pressure (determined by SWA), the maturation of the thalamocortical system (spindles), and the maturation of cortical connectivity (coherence). The crucial next step is to extend this concept to clinical groups to objectively characterise infants' sleep behaviours 'at risk' that foster later neurodevelopmental problems.

Exploring the Relationship Between Age at Nap Cessation and Social-Emotional Functioning in Children

OBJECTIVE

The objective of this study was to examine variations in age at nap cessation and identify whether there is an association with social-emotional functioning (SEF) as measured by internalizing/externalizing behavior, child temperament, and social skills in a sample of early childhood education and care-attending children.

METHODS

The sample comprised 1117 children from the Australian Effectiveness Early Educational Experiences for Children longitudinal early childhood study. We used children's age at nap cessation as retrospectively recalled by caregivers in 2011 or 2013 when children were between ages 2 and 7 years. Each child's SEF was reported by a caregiver using the Strengths and Difficulties Questionnaire, the Short Temperament Scale for Children, and the Social Skills Inventory Scale. Associations between children's age of nap cessation and SEF were tested using linear regressions.

RESULTS

The children's age at nap cessation ranged from 6 months to 6 years. For each additional year of napping, children's total , conduct , externalizing , and peer behavior problems decreased by 0.39 (95% confidence interval [CI], -0.70 to -0.09), 0.11 (95% CI, -0.21 to -0.01), 0.11 (95% CI, -0.51 to -0.06), and 0.11 (95% CI, -0.20 to -0.02) units on the Strengths and Difficulties Questionnaire scale, respectively. No further significant associations were found.

CONCLUSION

This is the first study reporting the age range of nap cessation and its associations with social-emotional functioning. Our findings demonstrate earlier cessation ages in Australian children attending Early Childhood Education and Care programs than previously reported and a small association with externalizing and peer problems.

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.

Infant sleep predicts trajectories of social attention and later autism traits

BACKGROUND

Children with neurodevelopmental disorders including autism spectrum disorder (ASD) and attention deficit hyperactivity disorder (ADHD) often experience sleep disturbances, but little is known about when these sleep differences emerge and how they relate to later development.

METHODS

We used a prospective longitudinal design in infants with a family history of ASD and/or ADHD to examine infant sleep and its relation to trajectories of attention and later neurodevelopmental disorders. We formed factors of Day and Night Sleep from parent-reported measures (including day/night sleep duration, number of naps in the day, frequency of night awakenings and sleep onset problems). We examined sleep in 164 infants at 5-, 10- and 14-months with/without a first-degree relative with ASD and/or ADHD who underwent a consensus clinical assessment for ASD at age 3.

RESULTS

By 14-months, infants with a first-degree relative with ASD (but not ADHD) showed lower Night Sleep scores than infants with no family history of ASD; lower Night Sleep scores in infancy were also associated with a later ASD diagnosis, decreased cognitive ability, increased ASD symptomatology at 3-years, and developing social attention (e.g., looking to faces). We found no such effects with Day Sleep.

CONCLUSIONS

Sleep disturbances may be apparent at night from 14-months in infants with a family history of ASD and also those with later ASD, but were not associated with a family history of ADHD. Infant sleep disturbances were also linked to later dimensional variation in cognitive and social skills across the cohort. Night Sleep and Social Attention were interrelated over the first 2 years of life, suggesting that this may be one mechanism through which sleep quality influences neurodevelopment. Interventions targeted towards supporting families with their infant's sleep problems may be useful in this population.

An infant sleep electroencephalographic marker of thalamocortical connectivity predicts behavioral outcome in late infancy

Infancy represents a critical period during which thalamocortical brain connections develop and mature. Deviations in the maturation of thalamocortical connectivity are linked to neurodevelopmental disorders. There is a lack of early biomarkers to detect and localize neuromaturational deviations, which can be overcome with mapping through high-density electroencephalography (hdEEG) assessed in sleep. Specifically, slow waves and spindles in non-rapid eye movement (NREM) sleep are generated by the thalamocortical system, and their characteristics, slow wave slope and spindle density, are closely related to neuroplasticity and learning. Spindles are often subdivided into slow (11.0-13.0 Hz) and fast (13.5-16.0 Hz) frequencies, for which not only different functions have been proposed, but for which also distinctive developmental trajectories have been reported across the first years of life. Recent studies further suggest that information processing during sleep underlying sleep-dependent learning is promoted by the temporal coupling of slow waves and spindles, yet slow wave-spindle coupling remains unexplored in infancy. Thus, we evaluated three potential biomarkers: 1) slow wave slope, 2) spindle density, and 3) the temporal coupling of slow waves with spindles. We use hdEEG to first examine the occurrence and spatial distribution of these three EEG features in healthy infants and second to evaluate a predictive relationship with later behavioral outcomes. We report four key findings: First, infants' EEG features appear locally: slow wave slope is maximal in occipital and frontal areas, whereas slow and fast spindle density is most pronounced frontocentrally. Second, slow waves and spindles are temporally coupled in infancy, with maximal coupling strength in the occipital areas of the brain. Third, slow wave slope, fast spindle density, and slow wave-spindle coupling are not associated with concurrent behavioral status (6 months). Fourth, fast spindle density in central and frontocentral regions at age 6 months predicts overall developmental status at age 12 months, and motor skills at age 12 and 24 months. Neither slow wave slope nor slow wave-spindle coupling predict later behavioral development. We further identified spindle frequency as a determinant of slow and fast spindle density, which accordingly, also predicts motor skills at 24 months. Our results propose fast spindle density, or alternatively spindle frequency, as early EEG biomarker for identifying thalamocortical maturation, which can potentially be used for early diagnosis of neurodevelopmental disorders in infants. These findings are in support of a role of sleep spindles in sensorimotor microcircuitry development. A crucial next step will be to evaluate whether early therapeutic interventions may be effective to reverse deviations in identified individuals at risk.

Maternal nighttime sleep and infant-mother attachment security: The mediating role of maternal parenting quality during bedtime and free play

The present study examined mothers' emotional availability (EA) during daytime free play and bedtime as a mediator of linkages between maternal nighttime sleep and infant-mother attachment. Participants included 153 mothers (85% White) with infants (53% female). When infants were 1, 3, 6, 9, and 12 months, maternal sleep was assessed using actigraphy and daily sleep diaries for 7 consecutive days. At each time point, mothers' EA was scored from one observation of daytime free play and from one evening observation of infant bedtime by trained observers who were blind to all other participant information. Average scores were created for maternal sleep and EA across the five occasions in the first year. At 12 and 18 months, infant-mother attachment security in the home was scored by blind observers using the Attachment Q-Set, averaged across the two age points, and used in analyses. Mediational analyses revealed that mothers who experienced highly variable sleep and had poor sleep quality were less emotionally available with infants at bedtime during infants' first year of life, which in turn was predictive of lower infant-mother attachment security in the second year, supporting mediation. Linkages between maternal sleep characteristics and daytime EA were less evident. Later maternal sleep timing was also directly predictive of low attachment security, after accounting for maternal EA. Findings emphasize that poor parental sleep places both parenting and infant socioemotional development at risk, and that parental sleep hygiene and sleep habits should be a salient focus of parenting intervention. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

Socioeconomic status and infant nighttime sleep across the second year of life: The moderating role of infant attachment security

This study examined socioeconomic status (SES) and attachment security as predictors of infant nighttime sleep during the second year. Participants included 128 mothers (86% White) with infants (48.4% boys). Data collection took place between April, 2009 and February, 2014. At 12, 18, and 24 months, infant sleep was assessed via actigraphy and daily diaries, and attachment with the Attachment Q-Set. SES indicators included income-to-needs ratios and education. Lower SES predicted greater variability in sleep duration and later sleep timing only for less secure infants. Less secure attachment was associated with poorer sleep at both between- and within-person levels, especially when infants were 12 months of age. Results emphasize the complex interactive effects of environmental and relational factors on infant sleep.

Sleep and Negative Affect Across Toddlerhood in the Context of Stress

Negative affect is associated with both high stress and poor sleep, but questions remain about the direction of these associations across time and interactions between stress and sleep, especially in early childhood. The present study examined sleep deficits, family stress, and observed negative affect in a sample of toddlers at 30, 36, and 42 months (N = 504). Negative affect was observed during a parent-child free play task. Sleep was measured via actigraphy. Stress was measured using a cumulative risk index of socioeconomic status, single parent status, household chaos, role overload, parenting hassles, social support, and stressful events. Findings showed few associations between sleep and negative affect, except for toddlers experiencing high levels of family stress. Toddlers experiencing both high stress and poor sleep demonstrated the highest levels of negative affect in the lab at 30 months. Adequate sleep may serve as a protective factor for children in high-stress families.

Association of transportation noise with sleep during the first year of life: A longitudinal study

STUDY OBJECTIVES

During infancy, adequate sleep is crucial for physical and neurocognitive development. In adults and children, night-time noise exposure is associated with sleep disturbances. However, whether and to what extent infants' sleep is affected, is unknown. Thus, this study investigated the relationship between nocturnal transportation noise and actimetry-derived habitual sleep behavior across the first year of life.

METHODS

In 144 healthy infants (63 girls), nocturnal (23:00-7:00) transportation noise (i.e., road, railway, and aircraft) was modelled at the infants' individual places of residence. Using actimetry, we recorded movement patterns for 11 days in a longitudinal design at 3, 6, and 12 months of age and derived the recently proposed core sleep composites of night-time sleep duration, activity, and variability. Using linear mixed-effects models, we determined associations between noise exposure and sleep composites. Sex, gestational age, parents' highest educational level, infants' age, and the existence of siblings served as control variables.

RESULTS

In models without interactions, night-time transportation noise was unrelated to sleep composites across the first year of life (p > .16). Exploratory analyses of an interaction between noise and the existence of siblings yielded an association between night-time transportation noise and sleep duration in infants without siblings only (p = .004).

CONCLUSION

In our study, sleep in infants during the first year of life was relatively robust against external perturbation by night-time transportation noise. However, particularly in children without siblings increasing night-time transportation noise reduced sleep duration. This suggests that the habitual noise environment may modulate individual susceptibility to adverse effects of noise on sleep.

From Alpha Diversity to Zzz: Interactions among sleep, the brain, and gut microbiota in the first year of life

Sleep disorders have been linked to alterations of gut microbiota composition in adult humans and animal models, but it is unclear how this link develops. With longitudinal assessments in 162 healthy infants, we present a so far unrecognized sleep-brain-gut interrelationship. First, we report a link between sleep habits and gut microbiota: daytime sleep is associated with bacterial diversity, and nighttime sleep fragmentation and variability link with bacterial maturity and enterotype. Second, we demonstrate a sleep-brain-gut link: bacterial diversity and enterotype are associated with sleep neurophysiology. Third, we show that the sleep-brain-gut link is relevant in development: sleep habits and bacterial markers predict behavioral-developmental outcomes. Our results demonstrate the dynamic interplay between sleep, gut microbiota, and the maturation of brain and behavior during infancy, which aligns with the lately emerging concept of a sleep-brain-gut axis. Importantly, sleep and gut microbiota represent promising health targets since both can be modified non-invasively. As many adult diseases root in early childhood, leveraging protective factors of adequate sleep and age-appropriate gut microbiota in infancy could constitute a health promoting factor across the entire human lifespan.

Effects of Touchscreen Media Use on Toddlers' Sleep: Insights from Longtime ECG Monitoring

Wearable biomedical sensor technology enables reliable monitoring of physiological data, even in very young children. The purpose of the present study was to develop algorithms for gaining valid physiological indicators of sleep quality in toddlers, using data from an undisturbing and easy-to-use wearable device. The study further reports the application of this technique to the investigation of potential impacts of early touchscreen media use. Toddlers' touchscreen media use is of strong interest for parents, educators, and researchers. Mostly, negative effects of media use are assumed, among them, disturbances of sleep and impairments of learning and development. In 55 toddlers (32 girls, 23 boys; 27.4 ± 4.9 months; range: 16-37 months), ECG monitoring was conducted for a period of 30 (±3) h. Parents were asked about their children's touchscreen media use and they rated their children's sleep quality. The use of touchscreen media predicted the physiologically determined quality of sleep but not parent-reported sleep quality (such as sleep onset latency). Greater heart rate differences between restless sleep phases and restful sleep indicated poorer nighttime recovery in children with more frequent use of touchscreen media. The study demonstrates that the expert analysis of the ECG during sleep is a potent tool for the estimation of sleep quality in toddlers.

A time series analysis of the relation between motor skill acquisition and sleep in infancy

To systematically examine the relation between motor milestone onset and disruption of night sleep in infancy, three families kept microgenetic, prospective, daily checklist diaries of their infants' motor behavior and sleep (197-313 observation days; 19,000 diary entries). Process control and interrupted time series analyses examined whether deviations from the moving average for night wakings and evening sleep duration were temporally linked to motor skill onset and tested for meaningful differences in individual sleep patterns before and after skill onset. Model assumptions defined skill onset as first day of occurrence or as mastery and moving average windows as 3, 7, or 14 days. Changes in infants' sleep patterns were associated with changing expertise for motor milestones. The temporal relation varied depending on infant and sleep parameter. Intensive longitudinal data collection may increase our understanding of micro-events in infant development.

Sleep behavior of infants with infantile hemangioma treated with propranolol-a cohort study

Sleep problems are frequently reported in infants treated with propranolol for infantile hemangiomas, possibly serving as a marker for a negative impact on central nervous system function. In this cohort study, we objectively investigate the sleep behavior of infants with infantile hemangiomas on propranolol compared to a healthy, untreated control group. Sleep of propranolol-treated infants and controls was investigated using ankle actigraphy and a 24-h diary for 7-10 days at ages 3 and 6 months. The main outcome measures were the Number of Nighttime Awakenings and Sleep Efficiency. The main secondary outcome measures included 24-hour Total Sleep, daytime sleep behavior, and parent-rated infant sleep quality and behavioral development based on the Brief Infant Sleep Questionnaire (BISQ) and the age-appropriate Ages-and-Stages Questionnaire (ASQ), respectively. Fifty-four term-born infants were included in each cohort. No group difference in any investigated parameter was seen at age 3 months. At age 6 months, the propranolol group exhibited a decrease in Sleep Efficiency and a trend towards an increased Number of Nighttime Awakenings compared to the control group. Treated infants at 6 months also had shorter daytime waking periods. 24-hour Total Sleep was unaffected by propranolol. No negative impact of propranolol on subjective sleep quality and behavioral development was noted.Conclusion: Propranolol exerts a measurable yet mild impact on objectively assessed infants' sleep measures. Behavioral developmental scores were unaffected. Our results support propranolol as first-line therapy for complicated infantile hemangiomas. What is Known: • Sleep disorders are frequently reported in infants with infantile hemangiomas treated with propranolol and often lead to treatment discontinuation. • Investigations of the sleep pattern in this patient group using objective measures are lacking. What is New: • The sleep pattern of propranolol-treated infants is assessed using actigraphy and a 24-h sleep diary and compared to healthy, untreated controls. • Propranolol leads to a decreased sleep efficiency at night and an increased demand of daytime sleep, yet effects are mild overall.