Exclusive breastfeeding at three months and infant sleep-wake behaviors at two weeks, three and six months

Maturation of infant sleep during the first 6 months of life: a mini-scoping review

Introduction

Several foundational aspects of neurodevelopment occur during the early months of infant life, most notably the maturation and consolidation of wake/sleep cycles. Past studies have had difficulty quantifying infant sleep, with most researchers relying on low-resolution caregiver surveys. Data obtained from nightly measurements have not yet been aggregated across studies to clarify developmental trajectories and population norms. This mini-scoping review assesses data collected from actigraphy and sleep diaries; the two most common nightly infant sleep measurement techniques.

Methods

The PubMed database was used to identify studies from 2000 to 2024 utilizing actigraphy and/or sleep diaries, and which report total night sleep (TNS), longest sleep stretch (LSS), and/or frequency of night wakings (NW) during the first 6 months of life. Data was then compiled per metric to reveal the extent of inter-and intra-study variability, and curves were fit to highlight developmental trajectories.

Results

A total of 35 articles met inclusion criteria (16 studies using actigraphy only, 8 studies using sleep diary only, and 11 studies using both actigraphy and sleep diaries). The sample sizes of these studies ranged from 13 to 320 infants. The majority of studies (N = 28) reported two or fewer age data points.

Conclusion

Aggregation and regression revealed longitudinal trends, but highlighted variability within and between studies, as well as systematic differences between measurement methods. In order to establish reliable benchmarks, future studies must include well defined, objective measures of sleep as well as greater methodological consistency, larger cohorts, more frequent sampling, and clear disclosure of methodological limitations.

Breast milk feeding practices and frequencies among complementary-fed children: a cross-sectional study in Northern Thailand

BACKGROUND

The available data on milk feeding patterns and feeding frequency during the complementary feeding phase are limited. This study aimed to examine breastfeeding practices and assess the associations between milk feeding type, feeding method, and feeding frequency among complementary-fed children.

METHODS

This cross-sectional study was conducted between January and May 2024 at well-baby clinics in Chiang Mai, Thailand, and included 1,122 parents of children aged 6-24 months. Milk feeding practices were assessed through 24-hour recall interviews and categorized by feeding type and feeding method. Subgroup analyses were conducted for bottle-fed and breastfed children. Poisson regression was used to evaluate the effect modifications of child age on daytime and nighttime feeding frequency across different feeding methods and types.

RESULTS

The overall prevalence of breastfeeding was 46.3%, whereas bottle feeding was reported in 76.5% of the children. The average feeding frequency was 5.8 times per 24 h, with 2.1 feedings occurring at night. Among children who exclusively consumed breast milk until 18-24 months, 95.2% were fed directly from the breast. Compared with a single milk type or a single feeding method, the trend of partial breastfeeding and combined feeding methods was associated with significantly higher feeding frequencies. At night, children who were exclusively formula-fed or bottle-fed had fewer nighttime feedings than those who were exclusively breastfed or directly breastfed at 12, 18, and 24 months. However, subgroup analysis revealed minimal differences in nighttime feeding frequency between the feeding groups.

CONCLUSIONS

This study revealed a high prevalence of discontinued breastfeeding and bottle feeding among young children. For those who continued exclusive breast milk consumption until nearly two years of age, direct breastfeeding remained the predominant feeding method. The associations between feeding method and milk type with feeding frequency were more pronounced during the daytime. However, at night, the relationships between feeding frequency and these factors were less consistent in both the overall and subgroup analyses, suggesting that nighttime feeding frequency is likely influenced by multiple factors beyond milk type and feeding method. Future longitudinal studies are needed to identify additional determinants of feeding frequency and their implications for child health.

Exclusive breastfeeding mitigates the association between prenatal maternal pandemic-related stress and children sleep problems at 24 months of age

Infant sleep quality is increasingly regarded as an important factor for children long-term functioning and adaptation. The early roots of sleep disturbances are still poorly understood and likely involve a complex interplay between prenatal and postnatal factors. This study investigated whether exclusive breastfeeding during the first 6 months moderated the association between maternal prenatal pandemic-related stress (PRS) and sleep problems in 24-months children born during the COVID-19 pandemic. We also explored the potential contribution of maternal postnatal anxiety in these relations. Seventy-eight infants (50% males) and their mothers provided complete data from birth to 24 months. Between 12 and 48 h from birth, maternal PRS during pregnancy was retrospectively reported as well as maternal anxiety and exclusive breastfeeding. Maternal anxiety and exclusive breastfeeding were also reported at 3 and 6 months after childbirth. Children sleep disturbances were reported at 24 months. Bayesian analyses revealed that maternal PRS was positively associated with sleep problems in children who were not exclusively breastfed from birth to 6 months. Findings add to the growing literature on the lasting impact of early pre- and postnatal experiences on child well-being and development.

Maternal depressive symptoms and mother-infant cosleeping (including room sharing and bedsharing): a systematic review

STUDY OBJECTIVES

Maternal depressive symptoms (MDS) affect most women during the first year postpartum. Mothers provide most of the nighttime care for infants, so studying the relationship between MDS and infant sleep location (ISL) is highly relevant to understanding maternal mental health over the first year of life and beyond. Infant sleep is studied by anthropologists, health care providers, and psychologists, with very little communication across disciplines. This review aimed to determine whether there is a predictive relationship between MDS and ISL.

METHODS

This systematic review searched 6 databases with terms related to maternal mood and ISL. Final analysis included 14 published studies, analyzed with narrative synthesis and Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Included studies directly compared ISL and MDS.

RESULTS

Five studies showed no relationship between ISL and MDS, and 1 study found bedsharing reduced MDS. Five studies found cosleeping was related to higher MDS although directionality is mixed or missing, and 3 studies found an association at some ages or for some populations only. Examining studies according to type of infant sleep assessment, study design, age of infant, or breastfeeding status failed to detect consistent patterns.

CONCLUSIONS

A variety of study designs, types and definitions of variable measures, sample recruitment, and study outcomes prevent detection of a consistent relationship between MDS and ISL. We explore reasons for the elusive nature of a relationship and make recommendations for future research in MDS and ISL, including crossdisciplinary collaborations.

CITATION

Barry ES, D'Souza L. Maternal depressive symptoms and mother-infant cosleeping (including room sharing and bedsharing): a systematic review. J Clin Sleep Med. 2024;20(9):1517-1533.

To sleep or to breastfeed: Associations between feeding method and sleep in infants and children

AIM

This study aimed to understand the association between feeding method, specifically breastfeeding versus non-breastfeeding, at 6 and 12 months and infant sleep over the first 3 years of life.

METHODS

A sample of 444 mother-infant dyads from the Maternal Adversity, Vulnerability and Neurodevelopment cohort were analysed. Based on retrospective maternal reports between 3-24 months, infants' breastfeeding status was determined at 6 and 12 months. Nocturnal sleep duration, longest period of consecutive sleep, and total sleep over 24 h were measured by maternal reports at 6, 12, 24 and 36 months.

RESULTS

Generalized Estimating Equations revealed no significant association between feeding status, both at 6 and 12 months, and nocturnal sleep duration or total sleep over 24 h between 6-36 months (p > 0.05). However, breastfeeding at both 6 and 12 months was associated with shorter periods of consecutive sleep, at 6 and 12 months (p < 0.05) but not at 24 and 36 months (p > 0.05).

CONCLUSION

Our findings suggest that breastfeeding seems to be associated with more infant sleep fragmentation but not with total sleep duration in early infancy. However, this sleep fragmentation does not persist into later infancy and early toddlerhood.

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

BACKGROUND

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

AIM

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

STUDY DESIGN

Cross-sectional study.

SUBJECTS AND METHODS

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

OUTCOME MEASURES

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

RESULTS

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

CONCLUSIONS

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

Gastrointestinal Tolerance of an Infant Formula Manufactured from Extensively Hydrolysed Protein in Healthy Term Infants

The evaluation of secondary parameters of a prospective, randomised, controlled, multicentre intervention trial aimed to analyse gastrointestinal tolerance of an infant formula manufactured from extensively hydrolysed whey protein (eHF) compared to intact cow's milk protein (control formula, CF) in healthy term infants. Infants ≤ 25 days of age, who were exclusively formula-fed, were randomised to receive eHF or CF for at least three months up to 120 days of age. An exclusively breastfed reference group (BF) was included for descriptive comparison. Infants' gastrointestinal tolerance was evaluated based on stool parameters, the Amsterdam Infant Stool Scale (AISS), the Infant Gastrointestinal Symptom Questionnaire (IGSQ), and sleeping patterns. Of 359 infants included, 297 randomised (eHF: n = 149, CF: n = 148) and 41 BF infants completed the study per protocol. All tolerance parameters were comparable between eHF and CF. Stool was predominantly soft and yellow in colour. Stool was more frequently green in eHF than CF. BF infants had more frequent stools, which were mainly watery or soft and yellow, and comparable IGSQ scores (descriptive). Irrespective of group, all gastrointestinal and sleep parameters showed signs of maturation with increasing age. In conclusion, eHF showed gastrointestinal tolerance as good as CF in healthy infants. Both formulae were well-tolerated.

Does the feeding method affect the quality of infant and maternal sleep? A systematic review

Breastfeeding brings many benefits to both mother and infant. Although, many women stop breastfeeding their infants too soon. The perceived association between breastfeeding and sleep may influence their decision to terminate breastfeeding. In our systematic review, we focused on mapping the relationship between infant feeding method and total sleep time (TST), number of nocturnal awakenings, awakenings after sleep onset (WASO) of mothers and infants and sleep quality of mothers. We searched four databases according to selected keywords and inclusion criteria - articles published in peer-reviewed journals between 2012 and 2022; English language; a sample consisting of mothers, infants, or both (without psychiatric and health problems); a comparison of the sleep quality of breastfed and formula-fed children or breastfeeding and formula-fed mothers. We read 260 full texts of selected articles. A total of 35 articles were included in this review. Due to significant heterogeneity, meta-analysis was not possible to accomplish. The results are processed according to narrative synthesis. Most studies agree that breastfed infants wake up more often at night. Total sleep time and time spent awake during the night (WASO) did not differ between breastfed and non-breastfed infants. We observed identical results in sleep variables among mothers. Additionally, there was no difference in maternal sleep quality. The synthesis revealed that the results may have differed due to using subjective, objective methods or the infant's age. It is important to remember that night waking is a more complex concept. Infants wake for many reasons, not just due to breastfeeding. The narrative synthesis indicated that the chosen study design, measurement method, the variables, and the infant's age could influence outcomes. In addition, other variables appeared that may affect the entire process. Therefore, we recommend that attention be paid to this in future studies.

Possible contribution of better maternal psychological well-being to the acquisition of sleeping through the night in infants during the early postpartum period

The objective of this study was to elucidate whether better maternal psychological well-being contributes to the acquisition of "sleeping through the night" (STN) in infants during the early postpartum period. Fifty-two primiparous mothers completed the General Health Questionnaire-28 (GHQ-28) in the third trimester (prenatal) and when the conceptional ages of their babies reached 8-9 weeks (hereafter, 2 months), 12-13 weeks (3 months), and 16-17 weeks (4 months). They also recorded babies' nocturnal sleep patterns in a timetable for 5 consecutive days each month postpartum. "Regular STN" was defined when the mean of longest nocturnal sleep duration for 5 consecutive days was > 8 h or between 6 and 8 h with < 1.0 nocturnal awakenings. According to these criteria, a total of 14 infants (27 %) acquired regular STN at 4 months (referred to as "STN infants"), with STN infants showing a marked increase in longest nocturnal sleep duration and a decrease in nocturnal awakenings from 2 to 3 months of age. The mothers of STN infants demonstrated steady reductions in postnatal GHQ-28 scores and had significantly lower prenatal GHQ-28 scores compared with the mothers of non-STN infants (3.7 ± 3.0 vs. 6.4 ± 4.1, p = 0.027). In random forest models for binomial classification, both prenatal and postnatal (at 4 months) GHQ-28 scores were identified as significant covariates for distinguishing STN infants, and other important covariates, including weeks of delivery, stepfamily, birth weight of the infant, and maternal co-sleeping at bedtime, were selected. Among these covariates, maternal co-sleeping at bedtime had relatively stronger correlations with both STN infants (r = - 0.440) and prenatal maternal GHQ-28 scores (r = 0.377). In conclusion, because prenatal maternal psychological well-being was thought to predict the acquisition of STN in infants, infants born from mothers with better psychological well-being appear to have some advantages in acquiring STN. These cross-lagged correlations suggest that the pathway from mothers to infants may be mediated by certain parenting behaviors, such as maternal co-sleeping at bedtime.

The Relationship Between Maternal and Infant Sleep Duration Across the First Two Years

OBJECTIVES

The first objective of this study was to determine how mother-infant sleep duration is related across the first 2 years of life. The second objective was to determine whether these relationships change across the first 2 years of life. The third objective was to understand demographic and health predictors of the relationship between maternal and child sleep.

METHODS

Parents of 464 infants from the STRONG Kids 2 study reported their own and infants' nocturnal sleep duration and other health information (i.e., breastfeeding) at 3, 12, 18, and 24 months postpartum.

RESULTS

Latent transition models revealed 2 mother-infant sleep profiles exist at 3 to 24 months. The low maternal sleep ( LMS ) pattern was characterized by lower maternal sleep duration than the recommended amount and lower infant sleep duration. The average maternal sleep ( AMS ) pattern was characterized by average maternal sleep duration meeting the recommended standard and average infant sleep duration. Approximately half of the mothers who started in the LMS profile transitioned to the AMS profile after 12 months postpartum. The sleep profiles stabilized after 12 months postpartum with limited transitions across 12 to 24 months. More infant-signaled nighttime wakings, later bedtimes, more infant sleep problems, and more exclusive breastfeeding were predictors of being in the LMS profile.

CONCLUSION

Mother-infant sleep profiles stabilized after age 12 months, and mother-infant sleep profiles are driven by infant sleep quality during the night. The findings suggest the need to establish a healthy sleep routine for mothers and infants in the first year of life to promote longer-term sleep hygiene.

The efficacy of massage as a nightly bedtime routine on infant sleep condition and mother sleep quality: A randomized controlled trial

BACKGROUND AND PURPOSE

Infants' sleep disorders and parents' insufficient sleep are common problems in the infant care. The current study was conducted to assess the effectiveness of infant massage on infants' night-time sleep condition and mothers' sleep quality.

PROCEDURES

140 infants were randomly put into two different groups, experimental group with fifteen-minute bedtime messages for two weeks and the control group with normal infant routine care. The Brief Infant Sleep Questionnaire, a personal information submission form, and Pittsburgh Sleep Quality Index for the mothers were the tools used to gather data in this study.

RESULTS

Infants in experimental group showed meaningful differences in variables such as, sleep latency (P <  0001, eta = 0.099), number of night waking (P = 0.03, eta = 0.027) and longest continuous sleep period (P = 0.03, eta = 0.026). As for other variables no meaningful differences were observed. There wasn't meaningful difference in the mother's overall night-time sleep quality between the two groups (P = 0.184, eta = 0.012) except for the duration of the mother's night-time sleep (P = 0.028, eta = 0.026) and the reduction of maternal sleep disorder (P = 0.020 eta = 0.029).

CONCLUSION

The findings indicated that infants' bedtime massages would improve some of the sleep markers of mothers and infants, and therefore, can be suggested as a practical, harmless, and cost-free method to improve sleep.

Perinatal Physiological and Psychological Risk Factors and Childhood Sleep Outcomes: A Systematic Review and Meta-analysis

OBJECTIVES

The purpose of this study was to investigate the influence of maternal physiological and psychological factors during pregnancy and after birth on infant and children's sleep outcomes.

METHODS

Six databases were searched from inception to April 2021. Longitudinal studies that investigated the association of risk factors during and after pregnancy and children's sleep-related outcomes were included. Hedge's g and odds ratio were pooled as effect size with random effects model.

RESULTS

A total of 32 articles were included. Both prenatal maternal alcohol use (odds ratio [OR] = 1.85, 95% confidence interval [CI]: 1.04-3.28) and tobacco smoking (OR = 1.28, 95% CI: 1.01-1.62) were associated with shorter child sleep duration. Prenatal and postnatal maternal depression symptoms were associated with increased child sleep problems at age 6 months (OR = 1.97, 95% CI: 1.19-3.24, and 2.05, 95% CI: 1.37-3.07, respectively). Prenatal and postnatal maternal major depression disorders were associated with shorter sleep duration (Hedge's g = -0.97, 95% CI: -1.57 to -0.37) and lower sleep efficiency (Hedge's g = -1.44, 95% CI: -1.93 to -0.95). Prenatal anxiety had no impact on child sleep problems (OR = 1.34, 95% CI: 0.86-2.10).

CONCLUSION

Maternal pregnancy and obstetric factors and psychological factors are potential risk factors of poor child sleep health. Future research is warranted to better understand the impact of these risk factors on long-term child sleep outcomes and their potential mediating mechanisms.

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

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

Reasons mothers bedshare: A review of its effects on infant behavior and development

Bedsharing is controversial for nighttime caregiving in the U.S. today, as in most of the West. However, from the standpoint of evolutionary pediatrics, anthropology, and cultural psychology, bedsharing is not controversial at all, representing the context for human infant evolution and conferring a host of physiological benefits to the infant as well as the mother. In an effort to understand the rise in Western bedsharing in recent decades (and following Ball, 2002; McKenna & Volpe, 2007), Salm Ward (2015) systematically reviewed the literature on mother-infant bedsharing and identified ten reasons why mothers choose to bedshare: (1) breastfeeding, (2) comforting for mother or infant, (3) better/more sleep for infant or parent, (4) monitoring, (5) bonding/ attachment, (6) environmental reasons, (7) crying, (8) cultural or familial traditions, (9) disagree with danger, and (10) maternal instinct. The current paper offers the "review behind the review," highlighting the scientific evidence behind the reasons mothers give for their decision to bedshare, focusing on how mothers' decisions about infant sleep location influence infant behavior and development.

Association between breastfeeding and sleep patterns in infants and preschool children

BACKGROUND

Although most studies have reported unfavorable short-term effects of breastfeeding on early-childhood sleep-wake behaviors that potentially attenuate over time, findings have remained inconsistent.

OBJECTIVES

We assessed associations of breastfeeding with longitudinal day-, night-, and total-sleep trajectories and with sleep-wake behaviors in healthy infants and preschoolers.

METHODS

Caregivers of naturally conceived, term, singleton infants (n = 654) completed the Brief Infant Sleep Questionnaire (3, 6, 9, 12, 18, and 24 mo) and/or Children's Sleep Habits Questionnaire (54 mo), and provided information on their infants' breastfeeding status at 3 mo. Trajectory analyses derived 4 day- (n = 243), 3 night- (n = 248), and/or 4 total- (n = 241) sleep trajectories, each differing in length of sleep duration (short/moderate/long) and variability (variable/consistent). Sleep-wake behaviors from 3 to 24 mo (day/night/total-sleep durations and duration/number of night awakenings) were also assessed for associations with breastfeeding.

RESULTS

After adjusting for potential covariates, formula-fed infants, relative to fully breastfed (predominant or exclusive) infants, were significantly less likely to exhibit moderate (OR: 0.28; 95% CI: 0.11, 0.70) and long consistent (OR: 0.18; 95% CI: 0.07, 0.50) night-sleep trajectories and less likely to exhibit moderate (OR: 0.21; 95% CI: 0.07, 0.61) and long consistent (OR: 0.12; 95% CI: 0.04, 0.38) and long variable (OR: 0.16; 95% CI: 0.05, 0.56) total-sleep trajectories, instead of short variable night- and total-sleep trajectories. Partially breastfed infants did not differ from fully breastfed infants for both night- and total-sleep trajectories. No significant differences were found between all groups for day-sleep trajectories. Fully breastfed infants had longer night- (6, 9, 12, and 24 mo) and total- (3 and 12 mo) sleep durations than formula-fed infants, albeit a greater number of night awakenings (from 6 to 12 mo).

CONCLUSIONS

Despite more night awakenings, fully breastfed infants have overall longer night- and total-sleep durations (sleep trajectories) than formula-fed infants.

Type of Milk Feeding and Introduction to Complementary Foods in Relation to Infant Sleep: A Systematic Review

Inconsistent conclusions from infant sleep and feeding studies may influence parents feeding-related decisions. This study aimed to systematically review the existing literature on infant sleep and its relation to the timing of introduction to complementary foods and type of milk feeding to better understand their role(s) in infant sleep. Cohort, longitudinal, cross-sectional studies, and controlled trials were identified using online searches of five databases up to April 2020. Twenty-one articles with a total of 6225 infants under 12 months-of-age were eligible. Exclusively breastfed infants (≤6 months-of-age) had a greater number of night wakings, but most studies (67%) reported no difference in night-time and 24 h sleep duration compared to formula-fed infants. However, after 6 months-of-age, most studies (>65%) reported breastfed infants to sleep less in the night-time and over 24 h compared to formula-fed infants. Furthermore, studies reported no association between the timing of introduction to complementary foods and infant sleep duration (<12 months-of-age). Future studies using standardized methodologies and definitions, transdisciplinary expertise, and longitudinal design are required to better understand the complex role of feeding on sleep.

Associations between daily screen time and sleep in a racially and socioeconomically diverse sample of US infants: a prospective cohort study

OBJECTIVE

To determine the associations between screen media use and sleep throughout infancy (3-12 months).

DESIGN

Prospective Nurture birth cohort.

SETTING

North Carolina, USA, 2013-2015.

PARTICIPANTS

Women enrolled in their second to third trimester, completed a phone interview after birth, and completed home visits at 3, 6, 9 and 12 months post partum.

PRIMARY AND SECONDARY OUTCOME MEASURES

Women reported the usual hours their infants slept during the day and night and their infants' usual use of five screen media activities at 3, 6, 9 and 12 months post partum. Adjusted mixed-effects regression analyses modelled the associations between infant screen time and sleep outcomes while disaggregating the between-infant and within-infant effects.

RESULTS

Among 558 mother-infant dyads, 374 (67.0%) infants were black and 304 (54.5%) households earned <$20 000 per year. Half (254, 50.2%) of the infants engaged with screens at 3 months of age, while 326 (72.9%) engaged at 12 months. The median value of the average daily screen time over the study period was 50 (IQR: 10-141) min. Infant screen time was inversely associated with night-time sleep duration only when considering between-infant effects (adjusted beta: -2.9; 95% CI -5.9 to 0.0; p=0.054 for log-transformed screen time). Effects were stronger for television+DVD viewing specifically (adjusted beta: -5.2; 95% CI -9.1 to -1.4; p<0.01 for log-transformed television+DVD time). For example, an infant who averaged 1 hour of television+DVD viewing over the study period slept, on average, 9.20 (95% CI 9.02 to 9.37) hours per night by 12 months compared with 9.60 (95% CI 9.41 to 9.80) hours per night for an infant with no screen time over the study period. There were no significant within-infant effects between screen time and night-time sleep, and screen time was not associated with daytime sleep or night-time awakenings.

CONCLUSIONS

Screen time during infancy was inversely associated with night-time sleep duration; however, causal associations remain uncertain.

TRIAL REGISTRATION NUMBER

NCT01788644.

Sleep Consolidation, Sleep Problems, and Co-Sleeping: Rethinking Normal Infant Sleep as Species-Typical

Infants evolved in the context of close contact (including co-sleeping). Evolutionary context is rarely considered in psychological infant sleep research, and Western sleep researchers make assumptions about what optimal "normal" infant sleep is and how to achieve early, deep, infant sleep consolidation and avoid infant sleep problems. However, an evolutionary and anthropological view of infant sleep as species-typical recognizes that human evolution likely prepared the infant brain for optimal development within its evolutionary context - co-sleeping. Thus, "normal" infant sleep, sleep consolidation, and sleep problems should all be understood within the framework of co-sleeping infants, not the historically new-phenomenon of solitary-sleeping infants. Much work needs to be done in order to understand "normal" infant sleep as species-typical and how adaptive infants are to environments that stray from their evolutionary norm.

Influence of intra- and extrauterine factors on infant sleep in the first 6 months of life

OBJECTIVE

Infant sleep problems can affect the child's health. Maternal characteristics have been associated with the quality of infant sleep, but few studies have investigated the impact of intrauterine conditions. The aim of the study was to evaluate the association between adverse intrauterine environments (maternal smoking, hypertension, diabetes, and intrauterine growth restriction) and extrauterine factors on infant sleep in the first 6 months of life.

METHODS

Prospective cohort study, including singleton and at-term infants. Mothers were interviewed after delivery and at 30 days, 3 months, and 6 months of life. Socioeconomic, breastfeeding, and sleep data were self-reported by mothers using semi-structured interviews. Maternal stress (Perceived Stress Scale) and postpartum depression symptoms (Edinburgh Postpartum Depression Scale) were assessed.

RESULTS

There was no statistically significant association between intrauterine environments and the sleep of infants of the 359 mother-child dyads investigated. Total infant sleep time decreased from approximately 13-11h from 30 days to 6 months of age (p<0.001) and the longest period of uninterrupted sleep increased from approximately 4-6h during the same period (p<0.001). Breastfed infants slept longer in 24-h periods in the first month, but they woke up more often throughout the night when compared to infants receiving formula. Mothers with depressive symptoms reported increased sleep latency time.

CONCLUSIONS

Adverse intrauterine environments did not significantly affect sleep measures in the first 6 months of life. Maternal characteristics and practices, however, were associated with infant sleep, suggesting that environmental factors significantly contribute to sleep quality early in life.

Association between breastfeeding and new mothers' sleep: a unique Australian time use study

BACKGROUND

Infant sleep is of great interest to new parents. There is ongoing debate about whether infants fed with breastmilk substitutes sleep longer than those exclusively or partially breastfed, but what does this mean for the mother? What expectations are realistic for mothers desiring to exclusively breastfeed as recommended by health authorities? There are both biological and social influences on infant and maternal sleep. More accurate information on average maternal sleep hours for diverse feeding practices may help guide realistic expectations and better outcomes for mothers, infants and families.

METHODS

Using a unique time use dataset purposefully designed to study the time use of new mothers, this study investigated whether the weekly duration of maternal sleep, sleep disturbance, unpaid housework, and free time activities differed by detailed feeding method. The study collected 24/7 time use data from 156 mothers of infants aged 3, 6 and/or 9 months between April 2005 and April 2006, recruited via mother's groups, infant health clinics, and childcare services throughout Australia. Sociodemographic and feeding status data were collected by questionnaire. Statistical analysis used linear mixed modelling and residual maximum likelihood analysis to compare effects of different infant feeding practices on maternal time use.

RESULTS

There were no significant differences in time spent asleep between lactating and non lactating mothers, though lactating mothers had more time awake at night. Lactating mothers spent more time (8.5 h weekly) in childcaring activity (p = 0.007), and in employment (2.7 vs. 1.2 h, p < 0.01), but there were no significant differences in free time. Those not breastfeeding spent more time in unpaid domestic work. Exclusive breastfeeding was associated with reduced maternal sleep hours (average 7.08 h daily). Again, free time did not differ significantly between feeding groups. Exclusively breastfeeding mothers experienced reduced sleep hours, but maintained comparable leisure time to other mothers by allocating their time differently. Domestic work hours differed, interacting in complex ways with infant age and feeding practice.

CONCLUSIONS

Optimal breastfeeding may require realistic maternal sleep expectations and equitable sharing of paid and unpaid work burdens with other household members in the months after the birth of an infant.

Newly walking infants' night sleep impacts next day learning and problem solving

Sleep is part of the process that prepares children and adults for next day cognitive activity. Insufficient or fragmented sleep has a detrimental impact on subsequent encoding (Rouleau et al., 2002) and cognitive functioning (Joo et al., 2012). However, fragmented sleep early in life is a developmental norm, limiting the extent to which conclusions derived from older populations can be generalized. To directly test the continuity of this relationship, newly-walking infants' (N=58) sleep was monitored overnight using actigraphy. The next morning they were taught a motor problem-solving task. The task required infants to navigate through a tunnel to reach a goal at the other end. We coded infants' exploratory behaviors and the extent of training required to solve the task. Using a cluster analysis that accounted for exploratory behaviors and number of training prompts, infants were sorted into three profiles: those who found the task Easy to solve, those who found it Difficult, and those who Never solved it. Wake episodes and sleep efficiency were entered as predictors of cluster membership in a multinomial logistic regression. Of the infants who ultimately solved the task, those with more wake episodes and lower sleep efficiency had more difficulty. Specifically, fragmentation appeared to negatively impact preparedness to learn. Contrary to our expectations, infants who Never solved the task had the least fragmented sleep, indicating that an optimal level of fragmentation is needed for efficient problem-solving. For infants, some level of sleep fragmentation is needed the night before learning in order to solve a task efficiently. These findings highlight the interaction between developmental domains, from sleep quality to motor experience, and their impact on infant learning in real time.

Infant feeding practices and sleep at 1 year of age in the nationwide ELFE cohort

Sleep problems reported by parents affect 20% to 30% of infants. Few studies focused on the longitudinal association between infant feeding practices and sleep, especially in France. Analyses were based on 8,696 infants from the French national birth cohort ELFE. Collection of feeding practices from birth to 10 months allowed for the identification of trajectories of use of baby cereals and thickened formula by group‐based trajectory modelling and calculation of duration of any breastfeeding (BF) and age at complementary feeding introduction (CFI) excluding baby cereals. Total sleep duration (TSD), night waking (NW) and sleep onset difficulties (SOD) were reported at age 1. Associations between feeding and sleep were tested by multinomial logistic regressions. BF duration ≥6 months was associated with parent‐reported frequent NW, SOD and TSD ≤ 12 h/24 h at age 1. For TSD and SOD, this association was no longer significant after accounting for parental sleep‐related practices. Early use of baby cereals (≤5 months) was associated with poor sleep. Early CFI (<4 months) was associated with shorter TSD and SOD but not NW. Early use of thickened formula (only <6 months) was related to poor sleep at age 1 (NW and SOD), whereas late (around 6 months) use of thickened formula was associated with better sleep. BF duration ≥6 months was related to poor sleep at age 1 but not after adjustment on 1‐year parental sleep‐related practices except for NW. The use of baby cereals or early CFI was not related to better sleep at age 1.

What Is “Normal” Infant Sleep? Why We Still Do Not Know

The human need for sleep is universal and unquestioned; however, humans vary in their sleep needs according to age, individual differences, as well as cultural and social norms and practices. Therefore, what is “normal” in infant sleep and the development of sleep architecture in humans is highly dependent on biological and sociocultural variables as well as socially constructed assumptions about what infant sleep “should” look like. This paper uses a multidisciplinary approach to review papers from fields including pediatrics, anthropology, psychology, medicine, and sociology to understand “normal” infant sleep. Because human culture and behavioral practice changes much more quickly than evolved human biology, and because human evolutionary history occurred in the context of breastfeeding and cosleeping, new work in the field of infant sleep architecture development would benefit from a multidisciplinary approach. To come to a consensus about what is “normal” infant sleep, researchers must agree on underlying basic assumptions of infant sleep from which to ask question and interpret findings.

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.