Genetic and environmental influences on daytime and nighttime sleep duration in early childhood

The moderating role of early-life parental adverse and positive factors in the genetic and environmental contributions to objectively assessed sleep duration in middle childhood

Early-life positive and adverse parental factors, such as positive parent personality and parental stress, affect the environmental context in which children develop and may influence individual differences in children's sleep health. This study examined the moderating role of early-life parental factors in the heritability (i.e., the extent to which individual differences are due to genetic influences) of objectively assessed childhood sleep duration. A total of 351 families from the Arizona Twin Project were studied. Primary caregivers (95% mothers) reported on multiple dimensions of stress and facets of their own personality when the twins were 12 months old. Seven years later (Mage = 8.43 years, SD = 0.68), families completed a home visit, and twins (51% female; 57% White, 29% Hispanic; 30% monozygotic, 39% same-sex dizygotic, 31% other-sex dizygotic) wore actigraph watches to assess their sleep, with caregivers completing similar assessments on their personality attributes and stress. Early-life positive parent personality moderated the heritability of sleep duration (Δ-2LL [-2 log likelihood] = 2.54, Δdf = 2, p = .28), such that as positive parent personality increased, the heritability of duration decreased. Early-life parental stress also moderated the genetic contribution to sleep duration (Δ-2LL = 2.02, Δdf = 2, p = .36), such that as stress increased, the heritability of duration increased. Concurrent positive parent personality and parental stress composites showed similar patterns of findings. Results highlight the likely contribution of parent positive traits and adverse experiences to the etiology of children's sleep health, with genetic influences on children's sleep more prominent in "riskier" environments. Understanding how genetics and environments work together to influence the etiology of sleep may inform prevention programs.

Individualized approaches to pediatric chronic insomnia: Advancing precision medicine in sleep disorders

The manifestations of chronic insomnia undergo age-related changes. In younger infants and children, behavioral insomnia emerges as the most prevalent form and typically responds to behavioral interventions. However, distinct clusters of clinical presentations suggest the presence of various phenotypes, potentially implicating the primary involvement of specific neurotransmitters. These conceptualizations, coupled with genetic studies on pleiotropy and polygenicity, may aid in identifying individuals at risk of persistent insomnia into adulthood and shed light on novel treatment options. In school-age children, the predominant presentation is sleep-onset insomnia, often linked with nighttime fears, anxiety symptoms, poor sleep hygiene, limit-setting issues, and inadequate sleep duration. The manifestations of insomnia in adolescence correlate with the profound changes occurring in sleep architecture, circadian rhythms, and homeostatic processes. The primary symptoms during adolescence include delayed sleep onset, sleep misperception, persistent negative thoughts about sleep, and physiological hyperarousal-paralleling features observed in adult insomnia. An approach centered on distinct presentations may provide a framework for precision-based treatment options. Enhanced comprehension of insomnia's manifestations across diverse developmental stages can facilitate accurate assessment. Efforts to subtype insomnia in childhood align with this objective, potentially guiding the selection of appropriate treatments tailored to individual neurobiological, clinical, and familial features.

Group-based sleep trajectories in children and adolescents: A systematic review

Sleep is crucial for health and development. Evidence indicates that sleep changes over time and distinct subgroups may experience different longitudinal patterns. This study systematically reviewed the studies that used latent trajectory modeling to investigate sleep trajectories of children and adolescents aged 0-18 years, and summarized the associated determinants and health-related outcomes. We searched PubMed, Embase, CENTRAL, PsycINFO, and Web of Science, identifying 46 articles that met our criteria. To ensure the reliability of the review, only studies rated as good or fair in terms of methodological quality were included, resulting in a total of 36 articles. Group-based trajectories were identified on several sleep dimensions (i.e., sleep duration, general and specific sleep problems, and bed-sharing behavior) and three or four trajectories were reported in most studies. There was a convergence trend across sleep duration trajectories during the first six years of life. Studies on specific sleep problem (i.e., insomnia, night-waking, and sleep-onset difficulties) typically identified two trajectories: consistent, minimal symptoms or chronic yet fluctuating symptoms. Lower socioeconomic status, maternal depression, and night feeding behaviors were the most frequently reported determinants of sleep trajectories. Membership in a group with certain adverse patterns (e.g., persistent short sleep duration) was associated with increased risks of multiple negative health-related conditions, such as obesity, compromised immunity, neurological problems, substance use, or internalizing/externalizing symptoms. Generally, there is potential to improve the quality of studies in this field. Causality is hard to be inferred within the current body of literature. Future studies could emphasize early life sleep, incorporate more assessment timepoints, use objective measures, and employ experimental design to better understand changes of and mechanisms behind the various sleep trajectories and guide targeted interventions for at-risk subpopulations.

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.

Correlation Between Maternal Anxiety During Mid-Pregnancy and Subsequent Infant Sleep Issues: A Cross-Sectional Study from 2015 to 2016

Purpose

To explore the correlation between maternal anxiety during mid-pregnancy and infant sleep issues based on the anxiety status of mothers in mid-pregnancy.

Patients and Methods

A cohort of 2122 primigravida women from Ma'anshan City, Anhui Province, was followed from pregnancy until 6 months postpartum. The study analyzed the impact of maternal anxiety on infant sleep patterns, including primary caregivers, encompassing insufficient sleep duration, frequent nocturnal awakenings, prolonged nocturnal awakening durations, and elongated sleep latency.

Results

A total of 1891 mother-infant pairs were included in this analysis. After adjusting for confounding factors, a positive correlation was found between maternal anxiety during mid-pregnancy and insufficient sleep duration (OR=1.69, 95% CI:1.13-2.52), and elongated sleep latency (OR=2.26, 95% CI:1.61-3.18).

Conclusion

Maternal anxiety during mid-pregnancy is associated with sleep issues in infants. Addressing maternal mental health during pregnancy may enhance sleep quality for mothers and infants, promoting overall maternal-infant health.

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.

Childhood sleep: assessments, risk factors, and potential mechanisms

BACKGROUND

Sleep problem is a highly prevalent health issue among pediatric populations across the world. In this review, we aimed to identify risk factors contributing to sleep deficiency and poor sleep hygiene in children. Potential biological, psychosocial, and environmental mechanisms as well as research gaps in the literature are also discussed.

DATA SOURCES

A comprehensive search for relevant English language full-text, peer-reviewed publications was performed focusing on pediatric sleep studies from prenatal to childhood and adolescence in a variety of indexes in PubMed, SCOPUS, and Psych Info. Both relevant data based and systematic reviews are included.

RESULTS

This paper summarizes many risk factors for childhood sleep problems, including biological (e.g., genetics, gender, age and puberty, prenatal factors, postnatal factors); nutritional (e.g., macronutrients, micronutrients, omega-3 fatty acids, obesity); environmental (e.g., heavy metals, noise, light, air pollution); interpersonal (e.g., family, exposure to violence, screen media use, physical injury); and community/socioeconomic variables (e.g., racial/ethnicity and cultural factors, neighborhood conditions and socioeconomic status, school factors, public health disasters/emergencies), to better understand the development of sleep problems in children.

CONCLUSIONS

Poor childhood sleep is a multifactorial issue affected by a wide range of prenatal and early-life biological, environmental, and psychosocial risk factors and contributors. A better understanding of these risk factors and their mechanisms is an important first step to develop future research and prevention programs focusing on pediatric sleep problems.

Early nap cessation in young children as a correlate of language and psychosocial outcomes: Evidence from a large Canadian sample

OBJECTIVES

Most children stop napping between 2 and 5years old. We tested the association of early nap cessation (ie, children who stopped before their third birthday) and language, cognition functioning and psychosocial outcomes.

METHODS

Data were from a national, longitudinal sample of Canadian children, with three timepoints. Children were 0-to-1 year old at T1, 2-to-3 years old at T2, and 4-to-5 years old at T3. Early nap cessation was tested as a correlate of children's psychosocial functioning (cross-sectionally and longitudinally), cognitive function (longitudinally), and language skills (longitudinally). There were 4923 children (50.9% male; 90.0% White) and their parents in this study who were included in the main analyses. Parents reported on demographics, perinatal and developmental variables, child functioning, and child sleep. Children completed direct assessments of receptive language and cognitive ability. Nap cessation, demographic, and developmental-control variables were tested as correlates of cross-sectional and longitudinal outcomes using linear regression (with a model-building approach).

RESULTS

Early nap cessation correlated with higher receptive language ability (β = 0.059 ± 0.028) and lower anxiety (β = -0.039 ± 0.028) at T3, after controlling for known correlates of nap cessation, nighttime sleep, and other sociodemographic correlates of the outcomes. Cognitive ability, hyperactivity-inattention, and aggression were not correlated with nap cessation.

CONCLUSIONS

Early nap cessation is related to specific benefits (ie, better receptive language and lower anxiety symptoms). These findings align with previous research. Future research should investigate differences associated with late nap cessation and in nap-encouraging cultures, and by ethnicity.

Nocturnal sleep duration trajectories in early childhood and school performance at age 10 years

Sleep plays a fundamental role in brain development and resultant functions. The aim was to verify whether nocturnal sleep duration during early childhood has long-term associations with academic achievement at age 10 years. The present study is part of the Quebec Longitudinal Study of Child Development, a representative cohort of infants born in 1997-1998 in the province of Quebec, Canada. Children with known neurological conditions were excluded from this cohort. Four trajectories of parent-reported nocturnal sleep duration at ages 2.5, 3, 4, 5 and 6 years were determined using a SAS procedure named PROC TRAJ. Sleep duration at age 10 years was also reported. Teachers provided data on academic performance when the children were age 10 years. These data were available for 910 children (430 boys, 480 girls; 96.6% Caucasians). Univariate and multivariable logistic regressions were performed using SPSS. Children who slept less than 8 hr per night at 2.5 years but normalized later on (Traj1) had three-five times the odds of having grades below the class average in reading, writing, mathematics and science compared with children who slept sufficiently (Traj3-4: 10-11 hr per night). Children who slept about 9 hr per night throughout childhood (Traj2) had two-three times the odds of being below the class average in mathematics and science. Sleep duration at age 10 years was not correlated with the academic performance. These results point to the presence of a very important early period during which sufficient sleep is needed to fine-tune the functions necessary for academic achievement later on.

Non-pharmacological and melatonin interventions for pediatric sleep initiation and maintenance problems: A systematic review and network meta-analysis

Sleep initiation and maintenance problems are common in the pediatric population and while behavioral interventions are recommended, their efficacy remains to be evaluated in clinical trials. We conducted a systematic review and network meta-analysis to assess the efficacy of non-pharmacological treatments and melatonin for sleep initiation and maintenance problems in healthy pediatric populations. We included 30 studies in the systematic review and 15 in the meta-analysis. Three network meta-analyses were conducted for sleep onset latency (SOL), wake after sleep onset (WASO), and total sleep time (TST). For SOL variable, the results support greater effectiveness of light therapy and melatonin than evidence-based psychological interventions, whether implemented in combination with light therapy or not. Regarding WASO variable, evidence-based psychological interventions and a combination of those techniques plus light treatment were the most efficacious. Finally, for TST variable, a larger effect was shown for the combined treatment of evidence-based psychological intervention with light therapy in comparison to other interventions. In conclusion, we found a high variability between study protocols likely impacting the results of the meta-analysis. Future randomized control trials studies, stratified by pediatric age classes, are needed in order to provide clear suggestions in clinical settings.

Associations between sleep trajectories up to 54 months and cognitive school readiness in 4 year old preschool children

Purpose

This study explores the association between the duration and variation of infant sleep trajectories and subsequent cognitive school readiness at 48–50 months.

Methods

Participants were 288 multi-ethnic children, within the Growing Up in Singapore Towards healthy Outcomes (GUSTO) cohort. Caregiver-reported total, night and day sleep durations were obtained at 3, 6, 9, 12, 18, 24 using the Brief Infant Sleep Questionnaire and 54 months using the Child Sleep Habits Questionnaire. Total, night and day sleep trajectories with varying durations (short, moderate, or long) and variability (consistent or variable; defined by standard errors) were identified. The cognitive school readiness test battery was administered when the children were between 48 and 50 months old. Both unadjusted adjusted analysis of variance models and adjusted analysis of covariance models (for confounders) were performed to assess associations between sleep trajectories and individual school readiness tests in the domains of language, numeracy, general cognition and memory.

Results

In the unadjusted models, children with short variable total sleep trajectories had poorer performance on language tests compared to those with longer and more consistent trajectories. In both unadjusted and adjusted models, children with short variable night sleep trajectories had poorer numeracy knowledge compared to their counterparts with long consistent night sleep trajectories. There were no equivalent associations between sleep trajectories and school readiness performance for tests in the general cognition or memory domains. There were no significant findings for day sleep trajectories.

Conclusion

Findings suggest that individual differences in longitudinal sleep duration patterns from as early as 3 months of age may be associated with language and numeracy aspects of school readiness at 48–50 months of age. This is important, as early school readiness, particularly the domains of language and mathematics, is a key predictor of subsequent academic achievement.

Behaviour genetics and sleep: A narrative review of the last decade of quantitative and molecular genetic research in humans

During the last decade quantitative and molecular genetic research on sleep has increased considerably. New behavioural genetics techniques have marked a new era for sleep research. This paper provides a summary of the most important findings from the last ten years, on the genetic and environmental influences on sleep and sleep disorders and their associations with health-related variables (including anxiety and depression) in humans. In this review we present a brief summary of the main methods in behaviour genetic research (such as twin and genome-wide association studies). We then discuss key research findings on: genetic and environmental influences on normal sleep and sleep disorders, as well as on the association between sleep and health variables (highlighting a substantial role for genes in individual differences in sleep and their associations with other variables). We end by discussing future lines of enquiry and drawing conclusions, including those focused on problems and misconceptions associated with research of this type. In this last decade our knowledge about genetic and environmental influences on sleep and its disorders has expanded. Both, twin and genome-wide association studies show that sleep and sleep disorders are substantially influenced by genetic factors and for the very first time multiple specific genetic variants have been associated with sleep traits and disorders.

Association of Breastfeeding Practices During the First 3 Months with Infant Sleep Trajectories: A Prospective Cohort Study

BACKGROUND

Breastfeeding has numerous effects on maternal and child health. The effect of breastfeeding on infant sleep remains inconclusive.

OBJECTIVES

We aimed to examine whether full breastfeeding (FBF) during the first 3 mo is associated with longitudinal infant sleep trajectories in their first 2 y of life.

METHODS

The study was embedded in the Tongji Maternal and Child Health Cohort study. Information on infant feeding practices was collected at 3 mo of age, and maternal/child pairs were assigned to the FBF or the non-FBF group (including partially breastfeeding and exclusive formula feeding) on the basis of feeding practices during the first 3 mo of life. Sleep data of infants were obtained at 3, 6, 12, and 24 mo. Total, night, and day sleep trajectories across 3 to 24 mo were estimated with group-based models. Each sleep trajectory was differentiated on the basis of sleep duration at 3 mo (long/moderate/short) and the interval from 6 to 24 mo (moderate/short). Multinomial logistic regression was used to investigate the association of breastfeeding practices with infant sleep trajectories.

RESULTS

Among the 4056 infants studied, 2558 (63.1%) received FBF for 3 mo. When compared with FBF infants, non-FBF infants had shorter sleep duration at 3, 6, and 12 mo (P < 0.01). Non-FBF infants were more likely to experience Moderate-Short (OR: 1.31; 95% CI: 1.06, 1.61) and Short-Short (OR: 1.56; 95% CI: 1.12, 2.16) total sleep trajectories and more likely to experience Moderate-Short (OR: 1.84; 95% CI: 1.22, 2.77), and Short-Moderate (OR: 1.40; 95% CI: 1.06, 1.85) night sleep trajectories than FBF infants.

CONCLUSIONS

Full breastfeeding for ≥3 mo were positively associated with longer infant sleep duration. Infants fully breastfed were more likely to experience better sleep trajectories characterized by longer duration in their first 2 y of life. Full breastfeeding may benefit infants through healthy sleep.

Regular, intermittent, and spontaneous: Patterns of preschool Children's nap behavior and their correlates

BACKGROUND

Daytime sleep during the preschool years (i.e., 1-5-years-old) is characterized by high inter-child variability in several components of nap behavior, including nap duration, nap timing, and the proportion of sleep during daytime. We used an empirical approach to examine variations amongst children in these aspects of napping and investigated correlates of these components of nap behavior.

METHODS

A large, nationally representative sample (N = 702) of Canadian parents completed an online survey, including a one-month retrospective report of their 1.5-5 year old's daytime and nighttime sleep behavior and other questionnaires. To understand patterns of children's nap behaviors we applied Latent Profile Analysis (LPA) to typical nap duration, typical timing of naps, frequency of naps, proportion of sleep during the daytime, and the proportion of naps which were spontaneous (i.e., child just fell asleep). Then, multinominal logistic regression was used to examine correlates of profile membership.

RESULTS

Four profiles of children emerged: (1) regular nappers; (2) intermittent nappers; (3) spontaneous nappers; and (4) non-nappers. After controlling for demographic variables (e.g., child age, sex, ethnicity) and known correlates of napping behaviors (e.g., birthweight, nighttime sleep duration), profile membership was related to parents' beliefs about napping, parents' own nap behaviors, family functioning, and child nighttime sleep problems in a multinominal logistic regression.

CONCLUSIONS

An empirical approach aided in understanding the inter-child variability in napping amongst preschool-age children. Parental beliefs about napping and the home environment were shown to be critical factors influencing this variability.

Contributions of memory and brain development to the bioregulation of naps and nap transitions in early childhood

The transition from multiple sleep bouts each day to a single overnight sleep bout (i.e., nap transition) is a universal process in human development. Naps are important during infancy and early childhood as they enhance learning through memory consolidation. However, a normal part of development is the transition out of naps. Understanding nap transitions is essential in order to maximize early learning and promote positive long-term cognitive outcomes. Here, we propose a novel hypothesis regarding the cognitive, physiological, and neural changes that accompany nap transitions. Specifically, we posit that maturation of the hippocampal-dependent memory network results in more efficient memory storage, which reduces the buildup of homeostatic sleep pressure across the cortex (as reflected by slow-wave activity), and eventually, contributes to nap transitions. This hypothesis synthesizes evidence of bioregulatory mechanisms underlying nap transitions and sheds new light on an important window of change in development. This framework can be used to evaluate multiple untested predictions from the field of sleep science and ultimately, yield science-based guidelines and policies regarding napping in childcare and early education settings.

Relations between sleep patterns early in life and brain development: A review

Sleep supports healthy cognitive functioning in adults. Over the past decade, research has emerged advancing our understanding of sleep's role in cognition during development. Infancy and early childhood are marked by unique changes in sleep physiology and sleep patterns as children transition from biphasic to monophasic sleep. Growing evidence suggests that, during development, there are parallel changes in sleep and the brain and that sleep may modulate brain structure and activity and vice versa. In this review, we survey studies of sleep and brain development across childhood. By summarizing these findings, we provide a unique understanding of the importance of healthy sleep for healthy brain and cognitive development. Moreover, we discuss gaps in our understanding, which will inform future research.

Heritability of Psychological Traits and Developmental Milestones in Infancy: A Systematic Review and Meta-analysis

Importance

Although infancy is the most rapid period of postnatal growth and development, factors associated with variation in infant traits are not well understood.

Objective

To synthesize the large twin study literature partitioning phenotypic variance in psychological traits and developmental milestones in infancy into estimates of heritability and shared and nonshared environment.

Data Sources

PubMed, PsycINFO, and references of included publications were searched up to February 11, 2021.

Study Selection

Peer-reviewed publications using the classical twin design to study psychological traits and developmental milestones from birth to 2 years old were included.

Data Extraction and Synthesis

Data were extracted in line with Preferred Reporting Items for Systematic Reviews and Meta-Analyses and categorized using the International Classification of Functioning, Disability and Health: Children and Youth Version. Data were pooled in 3-level random effects models, incorporating within-cohort variance in outcome measurement and between-cohort variance. Data were analyzed from March 2021 through September 2021.

Main Outcomes and Measures

The primary outcomes were monozygotic and dizygotic twin correlations. These were used to calculate genetic and shared and nonshared environment estimates.

Results

Among 139 publications that were systematically retrieved, data were available on 79 044 twin pairs (31 053 monozygotic and 47 991 dizygotic pairs), 52 independent samples, and 21 countries. Meta-analyses were conducted on psychological traits and developmental milestones from 106 publications organized into 10 categories of functioning, disability, and health. Moderate to high genetic estimates for 8 categories were found, the highest of which was psychomotor functions (pooled h2, 0.59; 95% CI, 0.25-0.79; P < .001). Several categories of traits had substantial shared environment estimates, the highest being mental functions of language (pooled c2, 0.59; 95% CI, 0.24-0.86; P = .001). All examined categories of traits had moderate or high nonshared environment estimates, the highest of which were emotional functions (pooled e2, 0.42; 95% CI, 0.33-0.50; P < .001) and family relationships (pooled e2, 0.42; 95% CI, 0.30-0.55; P < .001).

Conclusions and Relevance

These findings may be an important source of information to guide future gene discovery research, public perspectives on nature and nurture, and clinical insights into the degree to which family history and environments may estimate major domains of infant functioning, disability, and health in psychological traits and developmental milestones.

The Effectiveness of Sleep Training: Fact or Fiction?

Introduction

In Western cultures, parents often view infant sleep as problematic. Family, friends, and doctors may advise parents to “sleep train” assuming it is safe and effective, without considering its possible side effects, including its impact on breastfeeding. Unfortunately, it may reduce night feeds and result in earlier supplementation or weaning. The larger question is whether sleep training is worth the risk (i.e., does it improve infant sleep?). Our goal was to examine the data on the effectiveness of sleep training interventions on infant/toddler sleep.

Methods

PubMed and Google Scholar were searched for specific terms to identify articles that included behavioral sleep interventions and objective measures of sleep pre-and postntervention. Two objective infant sleep measures were examined: Night wakings and total sleep duration. Articles were then reviewed for evidence of the effectiveness of these interventions to reduce night wakings and increase total sleep duration.

Results

Five articles were identified that met the criteria for inclusion. Overall, there was no evidence that sleep training improves infant sleep.

Applications for Practice

The claim that sleep training is effective in changing infant sleep is not warranted. Given the potential side effects on breastfeeding, parents should be cautioned about engaging these behavioral sleep interventions if they have breastfeeding goals they want to achieve.

Early childhood sleep trajectories and association with maternal depression: a prospective cohort study

STUDY OBJECTIVES

To investigate trajectories of early childhood sleep in the first 3 years and their association with maternal depressive symptoms.

METHODS

Data were from 243 Chinese mother-child dyads. Children's sleep duration and night-waking were assessed using the Brief Infant Sleep Questionnaire (BISQ) at 42 days, 3, 6, 9, 12, 18, 24, and 36 months postpartum. The Center for Epidemiological Survey-Depression Scale (CES-D), Edinburgh Postnatal Depression Scale (EPDS), and Profile of Mood States (POMS) were used to assess maternal depressive symptoms at late pregnancy, 42 days, and 36 months postpartum, respectively. Early childhood sleep trajectories were estimated with group-based trajectory models. The association between early childhood sleep trajectories and maternal depressive symptoms was examined with binary and multinomial logistic regression models and linear regression models.

RESULTS

Three trajectories of daytime sleep duration ("short", 14.4%; "medium", 60.4%; "long", 25.2%), nighttime sleep duration ("increasing", 17.6%; "stable", 76.3%; "decreasing", 6.1%), and total sleep duration ("short", 21.5%; "medium", 59.9%; "long",18.6%), and two trajectories of night-waking ("resolving", 22.9%; "persistent", 77.1%) were identified. Controlling for confounding factors, maternal depression at 42 days postpartum was associated with higher risks for short daytime sleep duration and persistent night-waking in children. Persistent night-waking in children was associated with increased maternal depressive symptoms at 36 months postpartum.

CONCLUSION

Early childhood sleep follows distinct trajectories in the first 3 years of life. The trajectories of short daytime sleep duration and persistent night-waking are associated with maternal depression. The findings indicate tailored interventions should target both unfavorable early childhood sleep trajectories and maternal depression.

Does the maturation of early sleep patterns predict language ability at school entry? A Born in Bradford study

Children's vocabulary ability at school entry is highly variable and predictive of later language and literacy outcomes. Sleep is potentially useful in understanding and explaining that variability, with sleep patterns being predictive of global trajectories of language acquisition. Here, we looked to replicate and extend these findings. Data from 354 children (without English as an additional language) in the Born in Bradford study were analysed, describing the mean intercepts and linear trends in parent-reported day-time and night-time sleep duration over five time points between 6 and 36 months-of-age. The mean difference between night-time and day-time sleep was predictive of receptive vocabulary at age five, with more night-time sleep relative to day-time sleep predicting better language. An exploratory analysis suggested that socioeconomic status was predictive of vocabulary outcomes, with sleep patterns partially mediating this relationship. We suggest that the consolidation of sleep patterns acts as a driver of early language development.

Sleep ecology, sleep characteristics and behavior problems in young maltreated children: A scoping review

BACKGROUND

Behavior problems are highly prevalent in young maltreated children. Their etiology is multifactorial and has been widely documented. Lately, researchers paid increased attention to the role of sleep in non-maltreated children's behavior problems. They showed that poor sleep (e.g., short sleep duration, nocturnal awakenings) increased behavior problems. In addition, an inadequate sleep ecology (e.g., lack of sleep hygiene or bedtime routine) may lead to sleep problems.

OBJECTIVE

As maltreated children often live in disorganized environments, this study aims to map knowledge about sleep ecology and sleep characteristics, as well as their associations with behavior problems in young maltreated children from one to five years old.

METHOD

A scoping review was performed according to the PRISMA-SR checklist. Bibliographic databases were searched from 1993 to May 2020.

RESULTS

From the 650 studies screened, nine reported results about sleep ecology or sleep characteristics or their associations with behavior problems in young maltreated children. Only one study described their sleep ecology. Eight studies documented or compared sleep characteristics, showing slight differences between maltreated and non-maltreated children (e.g., longer nighttime sleep duration or shorter naps in maltreated children). Four studies revealed associations between sleep characteristics and behavior problems in young maltreated children (e.g., shorter sleep duration was associated with more externalizing behaviors).

CONCLUSION

Literature about sleep ecology, sleep characteristics, as well as with their associations with behavior problems in young maltreated children is scarce. Their sleep ecology especially deserves to be investigated. Longitudinal studies, studies with comparison groups, combining objective and subjective validated sleep measures, and taking into account maltreatment characteristics and children's developmental stage should be pursued.

Insufficient sleep during infancy is correlated with excessive weight gain in childhood: a longitudinal twin cohort study

STUDY OBJECTIVES

To examine total sleep duration in infancy and the associations of insufficient sleep duration with later weight gain and the risk of overweight in a longitudinal twin cohort study.

METHODS

The data for this study are from the Longitudinal Twin Study (LoTiS), a twin-pregnancy birth cohort study that was carried out in China (n = 186 pairs). The sleep data were collected at 6 months using the Brief Infant Sleep Questionnaire that was completed by parents with the assistance of a research assistant. Anthropometric data were obtained from the children's health clinic records at 6, 12, 18, and 24 months.

RESULTS

There were no significant differences between infants with insufficient sleep and those with sufficient sleep in terms of height, weight, body mass index, incidence of overweight, and body fat mass, while infants with insufficient sleep duration were predisposed to gain excessive weight from 6 to 12 and 6 to 18 months of age (all P < .05). After adjusting for confounding variables, insufficient sleep duration was found to be correlated with excessive weight gain from 6 to 18 months of age (odds ratio: 3.47; 95% confidence interval, 1.23-9.78). The relationship was more pronounced in monozygotic twins than in dizygotic twins.

CONCLUSIONS

Insufficient total sleep duration at the age of 6 months is correlated with the risk of excessive weight gain at 18 months of age in twins, particularly in monozygotic twins.

CLINICAL TRIAL REGISTRATION

Registry: Chinese Clinical Trial Register; Name: Unraveling the complex interplay between genes and environment in specifying early life determinants of illness in infancy: a longitudinal prenatal study of Chinese Twins. URL: http://www.chictr.org.cn/showproj.aspx?proj=13839; Identifier: ChiCTR-OOC-16008203.

CITATION

Yu J, Jin H, Wen L, et al. Insufficient sleep during infancy is correlated with excessive weight gain in childhood: a longitudinal twin cohort study. J Clin Sleep Med. 2021;17(11):2147-2154.

The Babytwins Study Sweden (BATSS): A Multi-Method Infant Twin Study of Genetic and Environmental Factors Influencing Infant Brain and Behavioral Development

Twin studies can help us understand the relative contributions of genes and environment to phenotypic trait variation, including attentional and brain activation measures. In terms of applying methodologies such as electroencephalography (EEG) and eye tracking, which are key methods in developmental neuroscience, infant twin studies are almost nonexistent. Here, we describe the Babytwins Study Sweden (BATSS), a multi-method longitudinal twin study of 177 MZ and 134 DZ twin pairs (i.e., 622 individual infants) covering the 5-36 month time period. The study includes EEG, eye tracking and genetics, together with more traditional measures based on in-person testing, direct observation and questionnaires. The results show that interest in participation in research among twin parents is high, despite the comprehensive protocol. DNA analysis from saliva samples was possible in virtually all participants, allowing for both zygosity confirmation and polygenic score analyses. Combining a longitudinal twin design with advanced technologies in developmental cognitive neuroscience and genomics, BATSS represents a new approach in infancy research, which we hope to have impact across multiple disciplines in the coming years.

Nighttime sleep duration trajectories were associated with body mass index trajectories in early childhood

BACKGROUND

The respective contribution of total, daytime and nighttime sleep duration in childhood obesity remains unclear.

OBJECTIVES

To assess the longitudinal association between developmental trajectories of sleep duration and BMI z-score in early childhood.

METHODS

Data were from the Melbourne INFANT program, a prospective cohort with 4-month-old infants being followed-up until age 60 months (n = 528). Sleep duration (total, daytime, nighttime) and BMI z-score were measured using questionnaire at ages 4, 9, 18, 43 and 60 months. Group-based trajectory modelling was used to describe longitudinal trajectories from ages 4 to 60 months. Multivariable logistic regression was conducted to assess the association between sleep duration and BMI z-score trajectories.

RESULTS

Three nighttime sleep duration trajectory groups were identified: "Long stable" (10.5 to 11.0 hours, 61%), "catchup long" (8.0 to 11.5 hours, 23%) and "short stable" (8.7 to 9.8 hours, 16%) nighttime sleepers. BMI z-score trajectory groups were classified as "low-BMIz" (-1.5 to -0.5 unit, 21%), "mid-BMIz" (-0.5 to 0.5 unit, 58%) and "high-BMIz" (0.8 to 1.4 unit, 21%). With adjustment for child and maternal covariates, both "catchup long" (OR 3.69 95%CI 1.74, 7.92) and "long stable" nighttime sleepers (OR 4.27 95%CI 2.21, 8.25) revealed higher odds of being in the "mid-BMIz" than the "high-BMIz" group. By contrast, total or daytime sleep duration trajectories were not associated with BMI z-score trajectories.

CONCLUSIONS

Longer nighttime, but not total or daytime, sleep duration was associated with lower BMI z-score trajectories in early childhood. Our findings reinforce the importance of nighttime sleep for healthy body-weight development in early childhood.

Correlates of Sleep Duration in Early Childhood: A Systematic Review

OBJECTIVE

This systematic review aimed to summarize correlates of sleep duration in children under 5 years of age.

METHODS

Six electronic databases (PubMed, PsycINFO, MEDLINE, CINAHL, SPORTDiscus, and Scopus) were searched from inception to May 2019. Observational studies and intervention studies reporting cross-sectional results from baseline data were considered. Data were extracted using a predesigned form and potential correlates were categorized following a sociological framework.

RESULTS

One-hundred and sixteen studies, representing 329,166 children, met the inclusion criteria, with a high risk of bias in 62 included studies. A total of 83 correlates of sleep duration were identified. Among the associations studied four or more times, correlates of nap duration were child's age and nighttime sleep onset/bedtime; correlates of nighttime sleep duration were household income, parent marital status, parental adiposity level, nighttime sleep duration at younger age, nighttime sleep onset/bedtime, nighttime sleep wakeup time, and frequency of current bedtime routine; correlate of total sleep duration was screen time.

CONCLUSIONS

Young children from low-income households, single families, or having overweight parents may be at risk for short sleep duration. Promoting healthy sleep duration from an early age appears essential. Effective practices may include encouraging an earlier bedtime, limiting screen time, and establishing a regular bedtime routine. The absence of consistent evidence in the psychological, cognitive, and emotional domain as well as the physical environmental domain warrants further research.

Heritability of sleep duration and quality: A systematic review and meta-analysis

Epidemiological and interventional research has highlighted sleep as a potentially modifiable risk factor associated with poor physical and mental health. Emerging evidence from (behavioral) genetic research also shows that sleep characteristics are under strong genetic control. With this study we aimed to meta-analyze the literature in this area to quantify the heritability of sleep duration and sleep quality in the general population. We conducted a systematic literature search in five online databases on January 24th 2020. Two authors independently screened 5644 abstracts, and 160 complete articles for the inclusion criteria of twin studies from the general population reporting heritability statistics on sleep duration and/or quality, and written in English. We ultimately included 23 papers (19 independent samples: 45,328 twins between 6 mo and 88 y) for sleep duration, and 13 papers (10 independent samples: 39,020 twins between 16 and 95 y) for sleep quality. Collectively, we showed that 46% of the variability in sleep duration and 44% of the variability in sleep quality is genetically determined. The remaining variation in the sleep characteristics can mostly be attributed to the unique environment the twins experience, although the shared environment seemed to play a role for the variability of childhood sleep duration. Meta-analyzed heritability estimates for sleep duration, however, varied substantially with age (17% infancy, 20-52% childhood, 69% adolescence and 42-45% adulthood) and reporter (8% parent-report, 38-52% self-report). Heritability estimates for actigraphic and Polysomnography (PSG)-estimated sleep were based on few small samples, warranting more research. Our findings highlight the importance of considering genetic influences when aiming to understand the underlying mechanisms contributing to the trajectories of sleep patterns across the lifespan.

Variations in longitudinal sleep duration trajectories from infancy to early childhood

OBJECTIVE

This study investigates variations in night, day, and total sleep trajectories across infancy and childhood in Asian children.

PARTICIPANTS

Participants consisted of a subset of 901 children, within the Growing Up in Singapore Towards healthy Outcomes cohort, which recruited 1247 pregnant women between June 2009 and September 2010.

DESIGN

We used a novel conditional probabilistic trajectory model: a probabilistic model for mixture distribution, allowing different trajectory curves and model variances among groups to cluster longitudinal observations. Longitudinal sleep duration data for the trajectory analyses were collected from caregiver-reported questionnaires at 3, 6, 9, 12, 18, 24, and 54 months.

RESULTS

We found 3 patterns of night sleep trajectories (n = 356): long consistent (31%), moderate consistent (41%), and short variable (28%); and 4 patterns of day sleep trajectories (n = 347): long variable (21%), long consistent (20%), moderate consistent (34%), and short consistent (25%). We also identified 4 patterns of total sleep trajectories (n = 345): long variable (19%), long consistent (26%), moderate consistent (28%), and short variable (27%). Short, moderate, and long trajectories differed significantly in duration. Children with consistent trajectories also displayed sleep patterns that were significantly more representative of typical developmental sleep patterns than children with variable trajectories.

CONCLUSIONS

This is the first study to describe multiple sleep trajectories in Singaporean children and identify between-individual variability within the trajectory groups. Compared to predominantly Caucasian samples, night/total sleep trajectories were generally shorter, while day sleep trajectories were longer. Future studies should investigate how these variations are linked to different developmental outcomes.

Neonatal irritable sleep-wake rhythm as a predictor of autism spectrum disorders

Recently, it has been suggested that sleep problems in autism spectrum disorder (ASD) not only are associated symptoms, but may be deeply related to ASD pathogenesis. Common clinical practice relating to developmental disorders, has shown that parents of children with ASD have often stated that it is more difficult to raise children in the neonatal period because these children exhibit sleep problems. This study investigated the possibility that abnormal neonatal sleep-wake rhythms are related to future ASD development.

We administered questionnaires to assess parent(s) of children with ASD and controls. A retrospective analysis was conducted among 121 children with ASD (94 male and 27 female children) recruited from the K-Development Support Center for Children (K-ASD), 56 children with ASD (40 male and 16 female children) recruited from the H-Children's Sleep and Development Medical Research Center (H-ASD) and 203 children (104 male and 99 female children) recruited from four nursery schools in T-city (control).

Irritable/over-reactive types of sleep-wake rhythms that cause difficulty in raising children, such as 1) frequently waking up, 2) difficulty falling asleep, 3) short sleep hours, and 4) continuous crying and grumpiness, were observed more often in ASD groups than in the control group. Additionally, the number of the mothers who went to bed after midnight during pregnancy was higher in the ASD groups than in the control group.

Sleep-wake rhythm abnormalities in neonates may be considerable precursors to future development of ASD. Formation of ultradian and postnatal circadian rhythms should be given more attention when considering ASD development. Although this is a retrospective study, the results suggest that a prospective study regarding this issue may be important in understanding and discovering intervention areas that may contribute to preventing and/or properly treating ASD.

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Neonatal irritable-type sleep-wake rhythmabnormalities are important precursors for futureASD development.

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Maternal lack of sleep and irregular lifestyle isrelated to increased risk of possibly developingfuture ASD.

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There is a possibility that proper intervention toabnormal sleep-wake rhythm may prevent thesubsequent onset of ASD.

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It is more logical to understand and interpret ASD,based on circadian rhythm and pineal glandfunction.

Sleep architecture is related to the season of PSG recording in 8-month-old infants

To date, little is known about the impact of season on infant sleep. In higher latitudes, the duration of daily light time varies substantially between different seasons, and environmental light is one potential factor affecting sleep. In this cohort study, one-night polysomnography (PSG) was performed on 72 healthy 8-month-old infants in 2012 and 2013 to study the effect of season on the sleep architecture of young infants in Finland. The children were divided into four subgroups, according to the amount of light during their birth season and the amount of light during the season of the PSG recordings, corresponding to spring, summer, autumn, and winter. We found that the season of birth did not have an impact on the infants' sleep architecture at 8 months of age, but the season of the PSG recording did have an effect on several sleep variables. In the PSGs conducted during the spring, there was less N3 sleep and more N2 sleep than in the PSGs conducted during the autumn. In addition, there was more fragmented sleep during spring than autumn. According to our data, the season has an effect on the sleep architecture of young infants and should, therefore, be considered when evaluating the PSG findings of young infants. The exact mechanisms behind this novel finding remain unclear, however. The findings imply that infants` sleep is affected by the season or light environment, as is the case in adult sleep. Since potential explanatory factors, such as direct natural or artificial light exposure and the melatonin levels of the infants, were not controlled, more research is needed in the future to better understand this phenomenon.

Child sleep and mother labour market outcomes

We show that sleep deprivation exerts strong negative effects on mothers' labour market performance. To isolate variations in maternal sleep, we exploit unique variations in child sleep disruption using a UK panel dataset that follows mother-child pairs through time. We find that sleeping one hour less per night on average significantly decreases maternal labour force participation, the number of hours worked and household income. We identify one mechanism driving the effects, namely the influence of maternal sleep on selection into full-time versus part-time work. Increased schedule flexibility for mothers with sufficient tenure mitigates the negative effects of sleep deprivation.

The Quebec Newborn Twin Study at 21

This paper is a revised and updated edition of a previous description of the Quebec Newborn Twin Study (QNTS), an ongoing prospective longitudinal follow-up of a birth cohort of twins born between 1995 and 1998 in the greater Montreal area, Québec, Canada. The goal of QNTS is to document individual differences in the cognitive, behavioral, and social-emotional aspects of developmental health across childhood, their early genetic and environmental determinants, as well as their putative role in later social-emotional adjustment, school, health, and occupational outcomes. A total of 662 families of twins were initially assessed when the twins were aged 6 months. These twins and their family were then followed regularly. QNTS now has 16 waves of data collected or planned, including 5 in preschool. Over the last 24 years, a broad range of physiological, cognitive, behavioral, school, and health phenotypes were documented longitudinally through multi-informant and multimethod measurements. QNTS also entails extended and detailed multilevel assessments of proximal (e.g., parenting behaviors, peer relationships) and distal (e.g., family income) features of the child's environment. QNTS children and a subset of their parents have been genotyped, allowing for the computation of a variety of polygenic scores. This detailed longitudinal information makes QNTS uniquely suited for the study of the role of the early years and gene-environment transactions in development.

Sleep education in primary school prevents future school refusal behavior

BACKGROUND

Sleep disorders, along with extreme difficulty in awakening, are one of the main causes of school refusal. The accumulation of chronic sleep deprivation accompanied by a late-night lifestyle is considered the basic inciting factor.

METHODS

From 2007, we initiated a sleep education program (Min-Iku) in Fukui, Japan, with the aim of improving pupil lifestyle and preventing future school refusal. All grade 1-6 Miyake-primary school (M-PS) pupils participated in this program and gave their informed consent. The Min-Iku included (i) implementation of a "daily life rhythm survey" by recording the sleep-wake rhythm in a table for 14 days; (ii) evaluation of the sleep table according to the classifications A-D; (iii) interviews of stage D children and their guardians; (iv) lectures on the importance of daily life rhythms for parents and teachers; and (v) 45 min classwork for all participating pupils.

RESULTS

In 2007, 10% of M-PS graduates developed school refusal behavior after entering Kaminaka junior high school (K-JHS). The incidence of school refusal, however, decreased each year after the implementation of the Min-Iku program and finally reached 0 by 2012. The sleep onset time of pupils improved each year, with the most common sleep time reaching 9:30 p.m. on both weekdays and holidays. With an earlier sleep time, the night-time sleep duration was significantly extended (P < 0.001 vs 2007 data).

CONCLUSION

The Min-Iku program for primary school pupils successfully achieved a more routine night-time sleep pattern and a regular life rhythm, which prevented school refusal during the subsequent JHS years.

Cross-cultural disparities of subjective sleep parameters and their age-related trends over the first three years of human life: A systematic review and meta-analysis

Changes in nighttime sleep consolidation and daytime discontinuation have been observed in early life. Yet information about societal or cultural factors remains scant for implementing sleep recommendations. We aimed to provide pooled estimates of subjective sleep duration, number of nightwakings and sleep timing; to describe their age-related trends; and to determine potential cross-cultural disparities between predominantly-Asian (PA) and predominantly-Caucasian (PC) regions during the first three years of life. We performed this review according to the PRISMA guidelines. Overall, 102 studies with 167,886 children aged 0-3 y from 26 different countries/regions were included. Compared to PC regions, PA toddlers had shorter sleep duration and more frequent nightwakings. When PC regions were further divided into Pacific Rim and Europe, differences were much more evident between PA and Pacific Rim for all nighttime sleep parameters. Trends of nighttime sleep duration and bedtime for PC regions showed rapid changes over the first 3-6 mo before stabilizing to a plateau, whereas a different change was found for PA regions. In conclusion, an apparent cross-cultural disparity of the subjective sleep parameters already exists in early childhood. Improved operationalization of sleep parameters and more objective evidence are needed to establish cultural-sensitive recommendations this early in life.

Sleep architecture is related to birth season in 1-month-old infants

Individual variation in sleep quality, quantity, and architecture is pronounced in small infants. Reasons for this remain largely unclear, even though environmental and genetic factors have been suggested to play a role. In order to study the effect of birth seasons on infant sleep architecture, 85 healthy 1-month-old infants underwent an overnight polysomnography (PSG). The PSGs were conducted in 2011-2013. The cohort was divided into four subgroups according to the amount of seasonal light at the time of birth, with each group covering a period of approximately three months. The groups were labeled IL (increasing light), L (light), ID (increasing darkness), and D (dark), corresponding to spring, summer, autumn, and winter, respectively. We found the amount of stage R sleep (precursor of REM sleep, formerly active sleep) to be the highest in infants born in summer, whereas infants born in winter presented the smallest amount of stage R sleep. Infants born in summer presented the smallest amount of stage T sleep (transitional sleep), while stage T sleep was most abundant in infants born in winter. In addition, infants born in summer showed the shortest total sleep time (TST) and the smallest number of awakenings during the study night. This was the first PSG study to find out that birth season modifies the sleep architecture of infants.

Variations in habitual sleep and relational memory in 6-month-olds

OBJECTIVES

Adequate sleep duration and good sleep quality are considered essential for development, especially during periods of major neurodevelopmental change. Still, relations between parent-reported habitual sleep and emerging cognitive abilities within the first year of life are not well studied. Here, we examined relations between habitual sleep measures and an aspect of cognitive functioning, relational memory, which emerges as early as 6 months of age, as compared to other abilities (ie, recognition memory and attentional orienting), both of which are considered to emerge earlier in development.

PARTICIPANTS

Participants were a subset of 267 healthy typically developing 6-month-olds taking part in the Growing Up in Singapore towards Healthy Outcomes cohort study.

MEASUREMENTS

Sleep duration, sleep latency, and number and duration of night awakenings were derived from the Brief Infant Sleep Questionnaire (BISQ). Short sleep was defined as <10 hours per day, categorized as "not recommended" based on the National Sleep Foundation recommendations. Associations between sleep variables and infants' performance on 2 relational memory tests (deferred imitation and relational binding) were examined independently using hierarchical (blockwise entry) linear regression. Associations between sleep and recognition memory and attentional orienting were also explored.

RESULTS

Habitual short sleepers had poorer relational memory recall in the deferred imitation task compared with 'typical' sleepers (10-18 hours per day). Shorter sleep latency was related to a greater proportion of correct responses for certain aspects of relational binding. There were no associations between sleep and recognition memory or attention.

CONCLUSIONS

Our findings suggest that habitual sleep duration and short sleep latency associate with 6-month-olds' relational memory, suggesting a preferential association with memory tasks that are sensitive to development during the second half of the first year.

Sleep Duration and Nocturnal Awakenings in Infants Born with Gestational Risk

OBJECTIVE

Infants born with gestation-related risks (low birth weight (LBW), small for gestational age (SGA), and prematurely born infants) are faced with a cascade of developmental issues. The aim of this study was to investigate whether infants with gestation-related risks have different patterns of parent-reported sleep duration and nocturnal awakenings than children without these risk factors.

METHODS

Information on sleep duration and nocturnal awakenings was obtained by parental report at age 6 and 18 months in the Norwegian Mother and Child Cohort Study, which is a population-based longitudinal pregnancy cohort study conducted at the Norwegian Institute of Public Health. Birth weight and gestational age were obtained from the Medical Birth Registry of Norway. Outcomes were related to birth weight, prematurity, and to being born SGA.

RESULTS

A total of 75,531 mother-child dyads were included. Compared with children without gestational risks, children born SGA and with LBW had shorter sleep duration, whereas children born prematurely had longer sleep duration at both time points. The infants born SGA and with LBW, but not the prematurely born children, had fewer nocturnal awakenings at 6 months, but all had more awakenings at 18 months.

CONCLUSION

Infants with gestation-related risks show distinct sleep patterns. We suggest that sleep assessment is included in the follow-up of high-risk infants. Future studies are needed to investigate the predictive value and functional importance of the sleep patterns for infants with gestation-related risks.

Environmental characteristics of early childhood education and care, daily movement behaviours and adiposity in toddlers: A multilevel mediation analysis from the GET UP! Study

STUDY OBJECTIVE

This study aimed to examine the direct effects of environmental characteristics of early childhood education and care (ECEC) centres on adiposity, and the indirect effects through daily movement behaviours (physical activity, sedentary time and naps).

METHODS

274 children (average age 19.73 ± 4.15 months) from 27 ECEC centres participated in this study. Environmental characteristics of ECEC centres were rated using the Infant/Toddler Environment Rating Scale-revised edition (ITERS-R). Daily movement behaviours were assessed using 24-h accelerometry. Body mass index z-scores were used to indicate adiposity.

RESULTS

There were no significant direct effects or indirect effects of environmental characteristics on toddlers' adiposity through daily movement behaviours. However, the environmental characteristics of "personal care routine" (B=0.72, p = 0.041) and "activity" (B = 0.87, p < 0.050) were positively associated with the percentage of time these toddlers spent in moderate-to-vigorous physical activity (MVPA). "Listening and talking" was also positively associated withnap(s) durations (B = 4.08 p = 0.001).

CONCLUSION

The relationships between environmental characteristics of ECEC centres and adiposity in toddlers, as well as, the mediating roles of daily movement behaviours still need confirmation by future longitudinal and experimental studies with long follow-up periods. At the same time, a broader spectrum of environmental characteristics of these settings needs to be examined with toddlers' adiposity in future studies; other potential mediators may also need to be taken into considerations.

Early Life Socioeconomic Disparities in Children's Sleep: The Mediating Role of the Current Home Environment

Despite identified concurrent socioeconomic disparities in children's sleep, little research has examined pathways explaining such associations. This study examined the quality of the home environment as a direct predictor of sleep and potential mediator of associations between early life socioeconomic status and objective and subjective indicators of sleep in middle childhood. A socioeconomically and ethnically diverse sample of 381 twin children (50% female; 46.6% lower middle class or living at or below the poverty line; 26% Hispanic/Latino) were assessed at 12 months for SES and eight years using gold-standard home environment interviews and actigraphy-measured sleep. Multilevel mediation path models indicated that lower early SES and lower quality concurrent home environments were associated with shorter sleep durations, longer sleep latencies, and greater sleep timing variability. The home environment significantly mediated associations with sleep duration and sleep timing variability. The findings illustrate an important target in the prevention of poor childhood and adolescent sleep.

Clinically Oriented Subtyping of Chronic Insomnia of Childhood

OBJECTIVES

To identify different profiles of pediatric insomnia, based on the most frequent clinical presentations (nocturnal awakenings, difficulty in falling asleep, nocturnal restlessness, early morning awakenings).

STUDY DESIGN

A structured parent interview was conducted in 338 children (mean age 21.29 months, SD 10.56) referred by pediatricians because of insomnia resistant to behavioral approaches and common drug treatments. The aim was to assess the characteristics of insomnia in children, together with family sleep-related history. A latent class analysis was run to identify profiles of insomnia. ANOVA and the χ² test were used to examine differences between profiles.

RESULTS

A 3-class model was built by latent class analysis: 17% (n = 58) of children constituted the first class, characterized by difficulties in falling asleep, with restlessness, nocturnal restlessness, and awakenings during the night; the second class, characterized by early morning awakenings, comprised 21% (n = 71) of children; 62% (n = 209) of children fell within the third class because of their high frequency of nocturnal awakenings and difficulties in falling asleep. The first class reported longer sleep latency and the presence of restless legs syndrome and anemia in the family history; depression and/or mood disorders were more frequent in class 2 and allergies and/or food intolerance were more frequent in class 3.

CONCLUSIONS

Our study suggests the existence of 3 different phenotypes of insomnia in children, based on clinical, personal, and familial data. The identification of these different phenotypes might help to optimize the assessment and treatment of insomnia in young children.

Environmental characteristics of early childhood education and care centres and young children's weight status: A systematic review

The aim of this systematic review was to summarize ECEC environmental correlates of weight status in children under the age of 6years. Six databases (PubMed, PsycINFO, CINAHL, SPORTDiscus, Scopus, and Web of Science) were searched until March 2017. Observational studies examining the relationship between ECEC environmental characteristics and weight status in children aged 0-6years were included. Data was extracted using a predesigned form. Eight studies, representing 4862 children, met the inclusion criteria. Twenty-two environmental characteristics were identified and classified into four domains (physical, political, economic, and sociocultural); of these, six correlates were found. 'Active environment' 'sedentary opportunities', 'active play time', 'high sugar and high fat served', 'educators' weight' and 'educators' habitual physical activity level' were associated with weight status in young children. However, for most environmental characteristics examined, strong evidence is not available yet, due to variations across studies on the measures of environmental characteristics and analytical methodologies. Stronger empirical evidence in greater quantity is needed. Future studies in this area are recommended to investigate the environmental influence using an ecological approach and to examine the potential mediators, with a focus on the settings of family-based centres and samples representing toddlers and/or infants.

Parent-Reported Symptoms of Sleep-Disordered Breathing Are Associated With Increased Behavioral Problems at 2 Years of Age: The Canadian Healthy Infant Longitudinal Development Birth Cohort Study

Study Objectives

To examine the association between the age of onset and duration of parent-reported symptoms of sleep-disordered breathing (SDB) and behavioral problems at age 2.

Methods

Parent-reported SDB symptoms were assessed quarterly between 3 months and 2 years among 583 Canadian Healthy Infant Longitudinal Development Edmonton-site participants. Parent-reported SDB symptoms were clustered into phenotypes using group-based trajectory analysis based on age of onset and duration of symptoms. Home-based polysomnography (PSG) was completed at 1 year. The Child Behavior Checklist preschool-version (Mean T-score 50, standard deviation 10 points) assessed total, externalizing (attention), and internalizing (anxiety, depression) behaviors at 2 years.

Results

Four phenotypes were identified: no SDB (64.7%), early-onset SDB (15.7%, peak symptoms at 9 months), late-onset (14.2%, peak symptoms at 18 months), and persistent SDB symptoms (5.3%, peak symptoms from 3 through 24 months). Persistent SDB (9.5 points, 95% CI 1.7, 17.2; p = .02) predicted the greatest magnitude of effect of total behavior problems, compared with children without SDB. Children with early-onset SDB (3.5 points, 95% CI 1.6, 5.4; p ≤ .001) and late-onset SDB (6.1 points 95% CI 4.0, 8.3; p ≤ .001) had increased total behavioral problems than children without SDB to 2 years. Additional analyses showed that the SDB phenotypes' trajectories were important for internalizing but not for externalizing behavior problems. There were no significant associations between home-PSG and parent-reported behavior problems.

Conclusions

Findings suggest that the age of onset and duration of parent-reported SDB symptoms prior to age 2 have adverse consequences for overall behavior problems.

Early Childhood Sleep Patterns and Cognitive Development at Age 6 Years: The Generation R Study

Objective

To explore the association of sleep duration and awakening frequency with cognitive outcomes in young children.

Methods

Mothers of 2,800 children from the Generation R cohort reported sleep duration and awakenings at children's age 24 months. At age 6 years, validated Dutch measures were used to assess children's nonverbal intelligence and language comprehension.

Results

We found a nonlinear association of total sleep time at 24 months with nonverbal intelligence ( p  = 0.03) and language comprehension ( p  = 0.04) at 6 years. Toddlers sleeping within the recommended 11-14 hr had more favorable cognitive development compared with both extremes. Frequent awakenings were negatively associated with nonverbal intelligence, but not with verbal comprehension.

Conclusion

Sleep duration in toddlerhood has an inverted-U-shaped relation with childhood cognitive measures. Frequent awakenings are associated with lower nonverbal intelligence. Given the marked decline in sleep duration and awakenings in toddlerhood, developmental changes of sleep patterns might be important for cognitive development.

Maternal Symptoms of Anxiety and Depression and Child Nocturnal Awakenings at 6 and 18 Months

Objective

We aim to estimate the pathways between maternal symptoms of anxiety and depression and child nocturnal awakenings via structural equation modeling using a sibling design.

Methods

Structural equation modeling on data from 14,926 sibling dyads or triads from the Norwegian Mother and Child Cohort Study.

Results

At 6 months, we estimated the association between maternal symptoms of anxiety and child nocturnal awakenings to be owing to several nonsignificant pathways. Child nocturnal awakenings at 18 months, however, were influenced by concurrent maternal symptoms of anxiety (β = .10) and depression (β = .12). Neither maternal symptoms of anxiety (β = .04) nor depression (β = -.00) was influenced by concurrent child nocturnal awakenings.

Conclusions

Our findings suggest that maternal mental health influences child sleep behavior at 18 months after birth, and not vice versa. This is in support of hypotheses on maternal mental health influencing child sleep during toddlerhood.

Sleep Characteristics and Temperament in Preterm Children at Two Years of Age

STUDY OBJECTIVES

We aimed to compare 2-year-old children born preterm with children born full term regarding: (1) sleep characteristics, (2) temperament, and (3) relations between sleep pattern and habits and temperament.

METHODS

The study included 51 preterm children with normal cognitive, language, and motor development (mean = 20.94 months, standard deviation [SD] = 4.08) and 57 full-term children (mean = 21.19, SD = 4.32). To assess sleep-related difficulties and habits and child temperament, mothers completed the following questionnaires: the (1) Sleep Disturbance Scale for Children-adapted (SDSC); (2) Brief Infant Sleep Questionnaire (BISQ); and (3) Italian Temperament Questionnaires-version 12-36 months (QUIT).

RESULTS

Preterm children needed less support to fall asleep and fell asleep more often alone in their own bed compared to those born at full term; however, preterm children showed more frequent sleep difficulties, such as restlessness and breathing problems during the night. In addition, preterm children had lower scores in the temperamental dimension of attention and higher scores in negative emotionality than full-term children. Finally, sleep problems were correlated with higher motor activity, lower social orientation and attention, and increased negative emotionality; a shorter nocturnal sleep duration was related to higher motor activity and lower inhibition to novelty whereas an earlier rise time was associated with lower attention and social orientation.

CONCLUSIONS

Preterm children showed sleep pattern problems and disturbance, predominance of attention problems, and negative emotionality related to sleep disruption.

Variants in calcium voltage-gated channel subunit Alpha1 C-gene (CACNA1C) are associated with sleep latency in infants

Genetic variants in CACNA1C (calcium voltage-gated channel subunit alpha1 C) are associated with bipolar disorder and schizophrenia where sleep disturbances are common. In an experimental model, Cacna1c has been found to modulate the electrophysiological architecture of sleep. There are strong genetic influences for consolidation of sleep in infancy, but only a few studies have thus far researched the genetic factors underlying the process. We hypothesized that genetic variants in CACNA1C affect the regulation of sleep in early development. Seven variants that were earlier associated (genome-wide significantly) with psychiatric disorders at CACNA1C were selected for analyses. The study sample consists of 1086 infants (520 girls and 566 boys) from the Finnish CHILD-SLEEP birth cohort (genotyped by Illumina Infinium PsychArray BeadChip). Sleep length, latency, and nightly awakenings were reported by the parents of the infants with a home-delivered questionnaire at 8 months of age. The genetic influence of CACNA1C variants on sleep in infants was examined by using PLINK software. Three of the examined CACNA1C variants, rs4765913, rs4765914, and rs2239063, were associated with sleep latency (permuted P<0.05). There was no significant association between studied variants and night awakenings or sleep duration. CACNA1C variants for psychiatric disorders were found to be associated with long sleep latency among 8-month-old infants. It remains to be clarified whether the findings refer to defective regulation of sleep, or to distractibility of sleep under external influences.