Rest-activity patterns of premature infants are regulated by cycled lighting

Practices for respecting the newborn's sleep-wake cycle: Interventional study in the neonatal intensive care unit

Objectives

Premature newborns are exposed to a great deal of over-stimulation, which can affect their cerebral development. For better sleep, certain practices should be recommended. The aim of this study was to evaluate the effect of a professional training program on the improvement of practices promoting respect for the newborn's sleep-wake cycle.

Materials and Methods

This was an interventional study with a longitudinal, single-group, and before-and-after design. The experimental design followed a three-stage time series: Eight months before, three months after, then eight months after intervention. It targeted a comprehensive sample of 66 professionals. It took place between October 2020 and March 2022 at the Neonatal Intensive Care Unit of the Hassan II University Hospital in Fez, Morocco. It was based on an observation grid and a self-administered questionnaire, validated and tested with a Cronbach's alpha reliability of 0.91.

Results

The light environment showed significant differences between the 1st and 3rd step (3.3% vs. 45.0%; P = 0.02; confidence interval [CI] = 13.644-10.456) for knowledge and (13.3% vs. 78.3%; P = 0.01; CI = 14.412-10.888) for practices; the noise environment showed a positive improvement between the 2nd and 3rd intervention (31.7% vs. 41.7%; P < 0.001; CI = 5.954-2.913) for knowledge and (65.0% vs. 73.3%; P < 0.001; CI = 3.597-1.236) for practices, with an average of (8.98 ± 0.30-28.15 ± 0.48; CI = 3.806-1.094) between the 1st and 3rd step. Practices surrounding sleep and wakefulness reported significant improvement between the three periods (14.35 ± 0.22 vs. 18.10 ± 0.35 vs. 19.90 ± 0.35; P P < 0.001; CI = 4.647-2.853) for sleep and (13.25 ± 0.48 vs. 22.27 ± 0.59; P < 0.001; CI = 10.563-7.471) for wakefulness with statistically significant correlations between knowledge and practices (0.426**) for sleep and (0.606**) for wakefulness.

Conclusion

The study demonstrated the positive impact of this sleep management and assessment program on the development of professional skills. Its implementation requires rigorous application of developmental support strategies for individualized care in neonatology.

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

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

A systematic review of chronobiology for neonatal care units: What we know and what we should consider

A Cochrane 2016 review indicated cycled light might benefit neonatal health in hospital. We systematically reviewed chronobiological factors for neonatal health in hospital units, identifying 56 relevant studies on light-dark cycles, feeding, noise, massage therapy, rooming-in, incubators vs. cribs, neonatal units vs. homes, and time-of-day of birth. Empirical evidence for benefits from chronobiology is weaker than expected, including light. Mechanisms of clinical benefits are unclear (e.g., changes to sleep/activity vs. other circadian-regulated processes). Regarding light, studies concerning sleep and circadian-related outcomes predominate; yet, neonatologists may be more interested in weight gain and time spent in hospital. Generalisability of findings is limited as most studies targeted neonates in stable condition and without congenital anomalies. Further research is needed, in particular concerning potential circadian entraining signals such as timing of meals or medications. Longer-term outcomes (regarding e.g., neurodevelopment and infection), and who may be at risk from time-of-day of birth effects and why remain to be explored. Overall, there is promise and ample scope for research into how chronobiological factors affect health in hospitalised neonates.

Effects of the neonatal intensive care environment on circadian health and development of preterm infants

The circadian system in mammals ensures adaptation to the light-dark cycle on Earth and imposes 24-h rhythmicity on metabolic, physiological and behavioral processes. The central circadian pacemaker is located in the brain and is entrained by environmental signals called Zeitgebers. From here, neural, humoral and systemic signals drive rhythms in peripheral clocks in nearly every mammalian tissue. During pregnancy, disruption of the complex interplay between the mother's rhythmic signals and the fetal developing circadian system can lead to long-term health consequences in the offspring. When an infant is born very preterm, it loses the temporal signals received from the mother prematurely and becomes totally dependent on 24/7 care in the Neonatal Intensive Care Unit (NICU), where day/night rhythmicity is usually blurred. In this literature review, we provide an overview of the fetal and neonatal development of the circadian system, and short-term consequences of disruption of this process as occurs in the NICU environment. Moreover, we provide a theoretical and molecular framework of how this disruption could lead to later-life disease. Finally, we discuss studies that aim to improve health outcomes after preterm birth by studying the effects of enhancing rhythmicity in light and noise exposure.

Designing artificial circadian environments with multisensory cares for supporting preterm infants' growth in NICUs

Previous studies suggest the importance of stable circadian environments for fetuses to achieve sound physiology and intrauterine development. This idea is also supported by epidemiological and animal studies, in which pregnant females exposed to repeated shifting of light-dark cycles had increased rates of reproductive abnormalities and adverse pregnancy outcomes. In response to such findings, artificial circadian environments with light-dark (LD) cycles have been introduced to NICUs to promote better physical development of preterm infants. Such LD cycles, however, may not be fully effective for preterm infants who are less than 30 weeks gestational age (WGA) since they are too premature to be adequately responsive to light. Instead, circadian rhythmicity of incubated preterm infants less than 30 WGA may be able to be developed through stimulation of the non-visual senses such as touch and sound.

Supporting and Enhancing NICU Sensory Experiences (SENSE), 2nd Edition: An Update on Developmentally Appropriate Interventions for Preterm Infants

The Supporting and Enhancing NICU Sensory Experiences (SENSE) program promotes consistent, age-appropriate, responsive, and evidence-based positive sensory exposures for preterm infants each day of NICU hospitalization to optimize infant and parent outcomes. The initial development included an integrative review, stakeholder input (NICU parents and healthcare professionals), and feasibility focus groups. To keep the program updated and evidence-based, a review of the recent evidence and engagement with an advisory team will occur every 5 years to inform changes to the SENSE program. Prior to the launch of the 2nd edition of the SENSE program in 2022, information from a new integrative review of 57 articles, clinician feedback, and a survey identifying the barriers and facilitators to the SENSE program's implementation in a real-world context were combined to inform initial changes. Subsequently, 27 stakeholders (neonatologists, nurse practitioners, clinical nurse specialists, bedside nurses, occupational therapists, physical therapists, speech-language pathologists, and parents) carefully considered the suggested changes, and refinements were made until near consensus was achieved. While the 2nd edition is largely the same as the original SENSE program, the refinements include the following: more inclusive language, clarification on recommended minimum doses, adaptations to allow for variability in how hospitals achieve different levels of light, the addition of visual tracking in the visual domain, and the addition of position changes in the kinesthetic domain.

Development of the circadian system in early life: maternal and environmental factors

In humans, an adaptable internal biological system generates circadian rhythms that maintain synchronicity of behavior and physiology with the changing demands of the 24-h environment. Development of the circadian system begins in utero and continues throughout the first few years of life. Maturation of the clock can be measured through sleep/wake patterns and hormone secretion. Circadian rhythms, by definition, can persist in the absence of environmental input; however, their ability to adjust to external time cues is vital for adaptation and entrainment to the environment. The significance of these external factors that influence the emergence of a stable circadian clock in the first years of life remain poorly understood. Infants raised in our post-modern world face adverse external circadian signals, such as artificial light and mistimed hormonal cues via breast milk, which may increase interference with the physiological mechanisms that promote circadian synchronization. This review describes the very early developmental stages of the clock and common circadian misalignment scenarios that make the developing circadian system more susceptible to conflicting time cues and temporal disorder between the maternal, fetal, infant, and peripheral clocks.

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

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

Integration of Time-Based Recommendations with Current Pediatric Health Behavior Guidelines: Implications for Obesity Prevention and Treatment in Youth

PURPOSE OF REVIEW

Youth-onset obesity is associated with negative health outcomes across the lifespan including cardiovascular diseases, type 2 diabetes, obstructive sleep apnea, dyslipidemias, asthma, and several cancers. Pediatric health guidelines have traditionally focused on the quality and quantity of dietary intake, physical activity, and sleep.

RECENT FINDINGS

Emerging evidence suggests that the timing (time of day when behavior occurs) and composition (proportion of time spent allocated to behavior) of food intake, movement (i.e., physical activity, sedentary time), and sleep may independently predict health trajectories and disease risks. Several theoretically driven interventions and conceptual frameworks feature behavior timing and composition (e.g., 24 h movement continuum, circadian science and chronobiology, intermittent fasting regimens, structured day hypothesis). These literatures are, however, disparate, with little crosstalk across disciplines. In this review, we examine dietary, sleep, and movement guidelines and recommendations for youths ages 0-18 in the context of theoretical models and empirical findings in support of time-based approaches. The review aims to inform a unifying framework of health behaviors and guide future research on the integration of time-based recommendations into current quantity and quality-based health guidelines for children and adolescents.

Length of stay and influencing factors of NICU in the Western Hunan, an underdeveloped area of China: A 9-year retrospective study

Objective

To investigate the factors that influence the length of stay (LOS) in a neonatal intensive care unit (NICU).

Methods

This retrospective study analysed clinical data from all newborns hospitalized in the NICU of a tertiary hospital in the Western Hunan area of China over a 9-year period (2012–2020). Factors associated with the LOS were analysed using univariate analysis and Cox regression analysis.

Results

A total of 16 094 newborns were included in the study: of which 9615 were inborn and 6479 were outborn newborns. There were 9482 males and 6612 females. Over the 9-year period, the mean LOS was 11.08 days (median LOS, 9.00 days; range, 1–141 days); and the LOS first increased, then decreased and stabilized. A LOS of 8–28 days was the most common duration (8849 of 16 094; 54.98%). Cox regression analysis demonstrated that sex, patient source, delivery method, gestational age, birth weight and comorbidities were significantly associated with LOS.

Conclusion

Being male, low gestational age and low birth weight increased the LOS. Reducing preterm and post-term infants, as well as eliminating comorbidities, could effectively shorten the LOS of newborns.

Birth, love, and fear: Physiological networks from pregnancy to parenthood

Pregnancy and childbirth are among the most dramatic physiological and emotional transformations of a lifetime. Despite their central importance to human survival, many gaps remain in our understanding of the temporal progression of and mechanisms underlying the transition to new parenthood. The goal of this paper is to outline the physiological and emotional development of the maternal-infant dyad from late pregnancy to the postpartum period, and to provide a framework to investigate this development using non-invasive timeseries. We focus on the interaction among neuroendocrine, emotional, and autonomic outputs in the context of late pregnancy, parturition, and post-partum. We then propose that coupled dynamics in these outputs can be leveraged to map both physiologic and pathologic pregnancy, parturition, and parenthood. This approach could address gaps in our knowledge and enable early detection or prediction of problems, with both personalized depth and broad population scale.

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Giving birth and caring for offspring are dynamic processes that can instill both love and fear.

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Maternal physiology continuously integrates fetal, social, and environmental cues.

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The result is coupled change in hormonal, autonomic nervous, and emotional output.

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Coupling may allow internal state to be assessed from peripheral autonomic markers.

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Such markers may identify healthy or pathologic pregnancy, parturition, and parenting, and enable creation of real-world tools.

Maturation of Arousals during Day and Night in Preterm Infants

The objective of this study was to compare the maturation of spontaneous arousals during day and night sleep in preterm and term infants. From the Autonomic Baby Evaluation study, the sleep and arousal characteristics of 12 preterm (35.1 ± 2.1 weeks’ gestational age, GA) and 21 term (39.8 ± 0.8 weeks GA) newborns were compared between diurnal and nocturnal sleep periods at birth (M0) and 6 months (M6) of age. Models were adjusted for time (night/day), maturation (M0/M6), prematurity (yes/no). We found that preterm infants had less active sleep (AS)% than term infants with maturation during both day and night sleep, which may reflect accelerated brain maturation secondary to stress or environmental exposure after birth. Moreover, there was a difference in arousal maturation during day and night sleep in the preterm infants, as shown previously for term infants, which suggests the emergence of a circadian rhythm during the earliest postnatal period. We also showed that compared to term infants, these moderate preterm infants had fewer total arousals and, more specifically, fewer arousals in AS during day and night sleep, exposing them to a higher risk of sudden infant death syndrome.

Influence of innate immune activation on endocrine and metabolic pathways in infancy

Prematurity is the leading cause of neonatal morbidity and mortality worldwide. Premature infants often require extended hospital stays, with increased risk of developing infection compared with term infants. A picture is emerging of wide-ranging deleterious consequences resulting from innate immune system activation in the newborn infant. Those who survive infection have been exposed to a stimulus that can impose long-lasting alterations into later life. In this review, we discuss sepsis-driven alterations in integrated neuroendocrine and metabolic pathways and highlight current knowledge gaps in respect of neonatal sepsis. We review established biomarkers for sepsis and extend the discussion to examine emerging findings from human and animal models of neonatal sepsis that propose novel biomarkers for early identification of sepsis. Future research in this area is required to establish a greater understanding of the distinct neonatal signature of early and late-stage infection, to improve diagnosis, curtail inappropriate antibiotic use, and promote precision medicine through a biomarker-guided empirical and adjunctive treatment approach for neonatal sepsis. There is an unmet clinical need to decrease sepsis-induced morbidity in neonates, to limit and prevent adverse consequences in later life and decrease mortality.

Beginning to See the Light: Lessons Learned From the Development of the Circadian System for Optimizing Light Conditions in the Neonatal Intensive Care Unit

The circadian timing system optimizes health by temporally coordinating behavior and physiology. During mammalian gestation, fetal circadian rhythms are synchronized by the daily fluctuations in maternal body temperature, hormones and nutrients. Circadian disruption during pregnancy is associated with negative effects on developmental outcomes in the offspring, highlighting the importance of regular and robust 24-h rhythms over gestation. In the case of preterm birth (before 37 weeks of gestation), maternal cues no longer synchronize the neonate's circadian system, which may adversely affect the neonate. There is increasing evidence that introducing robust light-dark cycles in the Neonatal Intensive Care Unit has beneficial effects on clinical outcomes in preterm infants, such as weight gain and hospitalization time, compared to infants exposed to constant light or constant near-darkness. However, the biological basis for these effects and the relationship with the functional and anatomical development of the circadian system is not fully understood. In this review, we provide a concise overview of the effects of light-dark cycles on clinical outcomes of preterm neonates in the NICU and its alignment with the development of the circadian system.

Promoting sound development of preterm infants in the name of developmental neuroscience: Beyond advanced life support and neuroprotection

Despite the increased survival opportunities for extremely preterm infants, their long-term cognitive outcomes remain poor, with increased incidence of cognitive impairments in childhood and reduced opportunities to attend higher education in young adulthood compared to their term-born peers. Given that a considerable fraction of preterm infants develop cognitive impairments even without apparent sentinel events at birth and cerebral lesions on MRI assessed at term equivalent age, future strategies to improve the outcome may need to address cerebral dysfunction, which cannot be explained by the classical understanding of the injury cascade triggered by hypoxia-ischaemia around birth. Developmental care has been proposed to minimize neurodevelopmental impairments related to preterm birth. However, considerable modes of cares, environmental settings and procedures provided by the developmental care of current style appear to offer little benefit to the sound development of infants. Although it is obvious that advanced life support and neuroprotective treatments fall far short in compensating for the burden of preterm birth, researchers need to make further effort to fill the knowledge gap in the cerebral function of foetuses and newborn infants before establishing evidence-based developmental care. Clinicians need to develop an ability to translate the findings from basic and translational studies incorporating their potential biases and limitations. Care for newborn infants needs to be reassessed, including but not limited to developmental care, in the context that any sensory input and motor reaction of preterm infants may ultimately affect their cognitive functioning.

The influence of feeding method on a mother's circadian rhythm and on the development of her infant's circadian rest-activity rhythm

An infant's circadian sleep-wake rhythm is established during the first three months after birth. It is crucial to identify how entrainment factors, such as maternal behavioural influences, feeding conditions, and others, contribute to the infant's obtaining circadian rhythm. This study examined the influence of feeding method on the mother's rhythm and on the development of her infant's circadian rest-activity rhythm. The subjects were 24 healthy primiparas (mean age, 29.8) and their full-term infants. We retrospectively divided the subjects into two groups based on feeding method (breastfeeding, 17; mixed-feeding, 7). Actographic recordings for the infants and their mothers were made over 3-5 consecutive days during the 2nd-3rd week, the 6th week, and the 12th week. First, we calculated the mean values of the autocorrelograms from the autocorrelation coefficients and calculated their statistical significance to see their rhythmicity for all the mothers and their infants at each of the periods. Second, we evaluated the mean values of the autocorrelograms to see statistical differences between the feeding methods. For the breastfed infants, the mean values of the autocorrelograms at 24-h for the 6th week were significant. However, the mean values for the mixed-fed infants were unclear. At the 12th week, the mean values of the autocorrelograms at 24-h for both groups of infants were significant. The mean value for the breastfeeding mothers at 24-h was significantly larger than that for the mixed-feeding mothers. In conclusion, the breastfeeding mothers contributed more to their infants achieving circadian rhythm than did the mixed-feeding mothers.

Biphasic Glucocorticoid Rhythm in One-Month-Old Infants: Reflection of a Developing HPA-Axis?

CONTEXT

The hypothalamus-pituitary-adrenal (HPA) axis displays a diurnal rhythm. However, little is known about its development in early life.

OBJECTIVE

To describe HPA-axis activity and study possible influencing factors in 1-month-old infants.

DESIGN

Observational.

SETTING

Amsterdam University Medical Center, location VU University Medical Center (VUMC), and Onze Lieve Vrouwe Gasthuis (OLVG), Amsterdam.

PARTICIPANTS

Fifty-five mother-infant pairs.

INTERVENTIONS

Collection of breast milk and infants' saliva 1 month postpartum for analysis of glucocorticoids (GCs; ie, cortisol and cortisone) using liquid chromatography- tandem mass spectrometry.

MAIN OUTCOME MEASURE

GC rhythm in infants' saliva and associations with vulnerability for maternal psychological distress (increased Hospital Anxiety and Depression Scale [HADS] score) or consultation at the Psychiatric Obstetric Pediatric (POP clinic), season at sampling, sex, and breast milk GC rhythmicity analyzed with SigmaPlot 14.0 software (Systat Software, San Jose, CA, USA) and regression analyses.

RESULTS

A significant biphasic GC rhythm was detected in infants, with mean peaks [standard error of the mean, SEM] at 6:53 am [1:01] and 18:36 pm [1:49] for cortisol, and at 8:50 am [1:11] and 19:57 pm [1:13] for cortisone. HADS score, POP consultation, season at sampling, and sex were not associated with the infants' GC rhythm. Breast milk cortisol maximum was positively associated with infants' cortisol area-under-the-curve (AUC) increase and maximum. Higher breast milk cortisone AUC increase, AUC ground, and maximum were associated with an earlier maximum in infants. Breast milk and infant GC concentrations were associated between 6:00 am and 9:00 am.

CONCLUSIONS

A biphasic GC rhythm, peaking in the morning and evening, was seen in 1-month-old infants at a group level. Breast milk GC parameters might be associated with the infants' GC rhythm, possibly caused by a signaling effect of breast milk GCs, or as an associative effect of increased mother-infant synchrony. These results contribute to an increased understanding of early life HPA-axis development.

A large-scale study reveals 24-h operational rhythms in hospital treatment

We found that orders and initial doses of treatment in the hospital were strongly influenced by time of day, regardless of drug type, diagnosis, or care unit. As the first large-scale account of 24-h rhythms in hospital medicine, this study identifies a potential operational barrier to best clinical care. Clinical decisions should be made around the clock; pain, infection, hypertensive crisis, and other conditions do not occur selectively in the morning. Systemic bias in the timing of medicine may also conflict with circadian biology, which can influence when certain treatments are most effective or safe. Our findings suggest that time of day in hospital operations deserves further consideration.

Hospitals operate 24 h a day, and it is assumed that important clinical decisions occur continuously around the clock. However, many aspects of hospital operation occur at specific times of day, including medical team rounding and shift changes. It is unclear whether this impacts patient care, as no studies have addressed this. We analyzed the daily distribution of ∼500,000 doses of 12 separate drugs in 1,546 inpatients at a major children’s hospital in the United States from 2010 to 2017. We tracked both order time (when a care provider places an electronic request for a drug) and dosing time (when the patient receives the drug). Order times were time-of-day−dependent, marked by distinct morning-time surges and overnight lulls. Nearly one-third of all 103,847 orders for treatment were placed between 8:00 AM and 12:00 PM. First doses from each order were also rhythmic but shifted by 2 h. These 24-h rhythms in orders and first doses were remarkably consistent across drugs, diagnosis, and hospital units. This rhythm in hospital medicine coincided with medical team rounding time, not necessarily immediate medical need. Lastly, we show that the clinical response to hydralazine, an acute antihypertensive, is dosing time-dependent and greatest at night, when the fewest doses were administered. The prevailing dogma is that hospital treatment is administered as needed regardless of time of day. Our findings challenge this notion and reveal a potential operational barrier to best clinical care.

Human milk as "chrononutrition": implications for child health and development

Human biology follows recurring daily rhythms that are governed by circadian cues in the environment. Here we show that human milk is a powerful form of "chrononutrition," formulated to communicate time-of-day information to infants. However, 85% of breastfed infants in the US consume some milk that does not come directly from the breast but is pumped and stored in advance of feeding. Expressed milk is not necessarily circadian-matched (e.g., an infant might drink breastmilk pumped in the evening on the following morning). Ingesting mistimed milk may disrupt infants' developing circadian rhythms, potentially contributing to sleep problems and decreased physiological attunement with their mothers and environments. Dysregulated circadian biology may compromise infant health and development. Despite wide-ranging public health implications, the timing of milk delivery has received little empirical study, and no major pediatric or public health organization has issued recommendations regarding the circadian-matching of milk. However, potential adverse developmental and health consequences could be ameliorated by simple, low-cost interventions to label and circadian-match stored milk. The current paper reviews evidence for human milk as chrononutrition and makes recommendations for future research, practice, and policy.

Potential Circadian Rhythms in Oligodendrocytes? Working Together Through Time

Oligodendrocytes (OL) are the only myelinating cells of the central nervous system thus interferences, either environmental or genetic, with their maturation or function have devastating consequences. Albeit so far neglected, one of the less appreciated, nevertheless possible, regulators of OL maturation and function is the circadian cycle. Yet, disruptions in these rhythms are unfortunately becoming a common "disorder" in the today's world. The temporal patterning of behaviour and physiology is controlled by a circadian timing system based in the anterior hypothalamus. At the molecular level, circadian rhythms are generated by a transcriptional/translational feedback system that regulates transcription and has a major impact on cellular function(s). Fundamental cellular properties/functions in most cell types vary with the daily circadian cycle: OL are unlikely an exception! To be clear, the presence of circadian oscillators or the cell-specific function(s) of the circadian clock in OL has yet to be defined. Furthermore, we wish to entertain the idea of links between the "thin" evidence on OL intrinsic circadian rhythms and their interjection(s) at different stages of lineage progression as well as in supporting/regulating OL crucial function: myelination. Individuals with intellectual and developmental syndromes as well as neurodegenerative diseases present with a disrupted sleep/wake cycle; hence, we raise the possibility that these disturbances in timing can contribute to the loss of white matter observed in these disorders. Preclinical and clinical work in this area is needed for a better understanding of how circadian rhythms influence OL maturation and function(s), to aid the development of new therapeutic strategies and standards of care for these patients.

Episodic Ultradian Events-Ultradian Rhythms

In the fast lane of chronobiology, ultradian events are short-term rhythms that have been observed since the beginning of modern biology and were quantified about a century ago. They are ubiquitous in all biological systems and found in all organisms, from unicellular organisms to mammals, and from single cells to complex biological functions in multicellular animals. Since these events are aperiodic and last for a few minutes to a few hours, they are better classified as episodic ultradian events (EUEs). Their origin is unclear. However, they could have a molecular basis and could be controlled by hormonal inputs-in vertebrates, they originate from the activity of the central nervous system. EUEs are receiving increasing attention but their aperiodic nature requires specific sampling and analytic tools. While longer scale rhythms are adaptations to predictable changes in the environment, in theory, EUEs could contribute to adaptation by preparing organisms and biological functions for unpredictability.

The human newborn's umwelt: Unexplored pathways and perspectives

Historically, newborns, and especially premature newborns, were thought to "feel nothing." However, over the past decades, a growing body of evidence has shown that newborns are aware of their environment, but the extent and the onset of some sensory capacities remain largely unknown. The goal of this review is to update our current knowledge concerning newborns' perceptual world and how ready they are to cope with an entirely different sensory environment following birth. We aim to establish not only how and when each sensory ability arises during the pre-/postbirth period but also discuss how senses are studied. We conclude that although many studies converge to show that newborns are clearly sentient beings, much is still unknown. Further, we identify a series of internal and external factors that could explain discrepancies between studies, and we propose perspectives for future studies. Finally, through examples from animal studies, we illustrate the importance of this detailed knowledge to pursue the enhancement of newborns' daily living conditions. Indeed, this is a prerequisite for assessing the effects of the physical environment and routine procedures on newborns' welfare.

Rhythms of life: circadian disruption and brain disorders across the lifespan

Many processes in the human body - including brain function - are regulated over the 24-hour cycle, and there are strong associations between disrupted circadian rhythms (for example, sleep-wake cycles) and disorders of the CNS. Brain disorders such as autism, depression and Parkinson disease typically develop at certain stages of life, and circadian rhythms are important during each stage of life for the regulation of processes that may influence the development of these disorders. Here, we describe circadian disruptions observed in various brain disorders throughout the human lifespan and highlight emerging evidence suggesting these disruptions affect the brain. Currently, much of the evidence linking brain disorders and circadian dysfunction is correlational, and so whether and what kind of causal relationships might exist are unclear. We therefore identify remaining questions that may direct future research towards a better understanding of the links between circadian disruption and CNS disorders.

The case for a chronobiological approach to neonatal care

Time of day is a critical factor for most biological functions, but concepts from the field of chronobiology have yet to be fully translated to clinical practice. Circadian rhythms, generated internally and synchronised to the external environment, promote function and support survival in almost every living species. Fetal circadian rhythms can be observed in utero from 30weeks gestation, coupled to the maternal rhythm, but synchronise to the external environment only after birth. Important cues for synchronisation include the light/dark cycle, the timing of feeding, and exposure to melatonin in breast milk. Disruption to these cues may occur during admission to the neonatal intensive care unit. This can impair the development of circadian rhythms, and influence survival and function in the neonatal period, with a potential to impact health and well-being throughout adult life. Here we outline the rationale and evidence to support a chronobiological approach to neonatal care.

Sensory exposure of neonates in single-room environments (SENSE): an observational study of light

OBJECTIVES

To measure the internal and external light exposure of incubators and open cots in an Australian single-room configured neonatal unit and compare findings to current recommendations.

METHODS

Light meters were placed in the internal and external environment of incubators and open cots within occupied single rooms in a tertiary-level neonatal unit between 15 September and 28 October 2015. Data were recorded in one-second increments over a minimum of 48 hours per room.

RESULTS

Internal median light in incubators and open cots predominantly fell below 50 lux, with low amplitude diurnal cycling. Incubator covers substantially reduced external light exposure, contributing to very low light conditions (<10 lux). Periodically, light inside incubators peaked six times greater than the maximum recommendation of 600 lux. Overall, internal incubator and open cot lighting in the neonatal unit met American Academy of Pediatrics and American College of Obstetricians and Gynecologists recommendations for 65.1% of the time during the day and 25.6% overnight. Australasian Health Infrastructure Alliance recommendations were met for 6.7% of the time during the day and 2.4% overnight.

CONCLUSIONS

Overall, light levels fell predominantly below 50 lux with peak periods of extreme light exposure. Low amplitude cyclic light was evident, but it remains unknown if this is sufficient to produce an effect on circadian entrainment, especially in preterm neonates. Current guidelines do not stipulate optimal cyclic light levels in neonatal units to promote circadian rhythms in the newborn population. Further research to determine well-defined lighting parameters for neonates of different gestations is paramount.

Control of Rest:Activity by a Dopaminergic Ultradian Oscillator and the Circadian Clock

There is long-standing evidence for rhythms in locomotor activity, as well as various other aspects of physiology, with periods substantially shorter than 24 h in organisms ranging from fruit flies to humans. These ultradian oscillations, whose periods frequently fall between 2 and 6 h, are normally well integrated with circadian rhythms; however, they often lack the period stability and expression robustness of the latter. An adaptive advantage of ultradian rhythms has been clearly demonstrated for the common vole, suggesting that they may have evolved to confer social synchrony. The cellular substrate and mechanism of ultradian rhythm generation have remained elusive so far, however recent findings—the subject of this review—now indicate that ultradian locomotor rhythms rely on an oscillator based on dopamine, dubbed the dopaminergic ultradian oscillator (DUO). These findings also reveal that the DUO period can be lengthened from <4 to >48 h by methamphetamine treatment, suggesting that the previously described methamphetamine-sensitive (circadian) oscillator represents a long-period manifestation of the DUO.

How to improve sleep in a neonatal intensive care unit: A systematic review

There is increasing evidence that sleep plays a major role in the development of neural pathways in the neonatal brain. Several studies have suggested evidence-based approaches to improve sleep for infants admitted to the neonatal intensive care unit (NICU); however, in many neonatal centers very few of these strategies seem to be implemented in routine care.

OBJECTIVE

To systematically review the literature to determine interventions promoting neonatal sleep on the NICU, in order to develop key guidelines to improve neonatal sleep.

METHODS

A systematic search was conducted according to the criteria of the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement for conducting and reporting systematic reviews. The search was performed in Pubmed, CINAHL and the Cochrane Library on 19 September 2016 and again on 28 January 2017.

RESULTS

In total, fourteen studies were included (10 RCT's and three quasi-experimental study designs): four studies were of high quality, eight of moderate quality and two of low quality. Two studies investigating kangaroo care reported significant effect on infant sleep behavior, two studies comparing Yakson and Gentle Human Touch (GHT) found significant effect on behavioral states and one study reported an increase in sleep behavior using different sleep surfaces. One study showed a significant effect on sleep patterns using music as an intervention and one study showed no significant effect using music. Two studies showed no significant effect on infant sleep using cycled light and different types of LED-light and one study showed significant effect of cycled lightning. There were no effects of Neonatal Individualized Developmental Care Program (NIDCAP) or massage therapy.

CONCLUSION

Although many different interventions have been reported to promote sleep in infants who require intensive care, there is great heterogeneity across studies: the methods of sleep assessment, the targeted sleep behaviors, and the study populations vary significantly across published reports. Based on the results there seems to be insufficient evidence to recommend any new intervention to promote neonatal sleep on the NICU. However because of the importance of sleep for the development of the neonatal brain we do suggest some key guidelines based on moderate evidence, expert opinion and parental values to improve sleep on the NICU and to direct future neonatal sleep studies.

Timing for the Introduction of Cycled Light for Extremely Preterm Infants: A Randomized Controlled Trial

Day-night cycled light improves health outcomes in preterm infants, yet the best time to institute cycled light is unclear. The hypothesis of this study was that extremely preterm infants receiving early cycled light would have better health and developmental outcomes than infants receiving late cycled light. Infants born at ≤28 weeks gestation were randomly assigned to early cycled light (ECL) starting at 28 weeks postmenstrual age [PMA] or late cycled light (LCL), starting at 36 weeks PMA. Daylight was 200-600 lux and night was 5-30 lux. Primary outcomes were weight over time and length of hospitalization. Secondary outcomes were hospital costs, sleep development, and neurodevelopment at 9, 18, and 24 months corrected age. Of 121 infants randomized, 118 were included in analysis. Weight gain in the two groups did not differ significantly but increased across time in both groups. In PMA weeks 36-44, the mean weight gain was 193.8 grams in the ECL group compared to 176.3 grams in the LCL group. Effect sizes for weight were Cohen d = 0.26 and 0.36 for 36 and 44 weeks PMA. Infants in the ECL group went home an average of 5.5 days earlier than the LCL group, but this difference was not statistically significant. There were no group differences on neurodevelopmental outcomes. Although statistically non-significant, clinically important differences of improved weight gain and decreased hospital stay were observed with ECL. The small observed effect sizes on weight during hospitalization should be considered in future cycled light research with extremely preterm infants. © 2017 Wiley Periodicals, Inc.

Effects of Cycled Lighting Versus Continuous Near Darkness on Physiological Stability and Motor Activity Level in Preterm Infants

BACKGROUND

Preterm infants generally spend weeks in the neonatal intensive care unit where light intensity can fluctuate as well as be high, leading to physiological instability and increased motor activity in these infants. To date, 2 lighting control methods have been studied: cycled lighting and continuous near darkness. The most appropriate method of lighting is still unknown due to ambivalent results from the studies that have assessed these 2 interventions.

OBJECTIVE

To compare the effects of cycled lighting versus continuous near darkness on physiological stability and motor activity level in preterm infants born between 28 and 32 weeks of gestation.

METHODS

A randomized clinical trial was conducted to compare physiological stability and motor activity level in preterm infants assigned to cycled lighting or continuous near darkness. Thirty-eight participants were recruited and randomly assigned to one of the lighting conditions for 24 hours. Physiological stability was measured using the Stability of the Cardiorespiratory System in Premature Infants (SCRIP) score, the means, and the coefficient of variation of each physiological parameter measured. The level of motor activity was measured with an accelerometer.

RESULTS

There were no significant differences between the 2 groups with regard to physiological stability measured by the SCRIP score, means, and coefficient of variation as well as motor activity level. Participants in both groups were physiologically stable and their motor activity level was comparable.

IMPLICATIONS FOR PRACTICE AND RESEARCH

Neither cycled lighting nor continuous near darkness negatively impacted infant's physiologic stability and motor activity level. Further research is required to identify the most appropriate lighting control method for preterm infants born between 28 and 32 weeks of gestation.

The effect of cycled lighting in the intensive care unit on sleep, activity and physiological parameters: A pilot study

Patients in intensive care suffer from severe illnesses or injuries and from symptoms related to care and treatments. Environmental factors, such as lighting at night, can disturb patients' circadian rhythms. The aim was to investigate whether patients displayed circadian rhythms and whether a cycled lighting intervention would impact it. In this pilot study (N=60), a cycled lighting intervention in a two-bed patient room was conducted. An ordinary hospital room functioned as the control. Patient activity, heart rate, mean arterial pressure and body temperature were recorded. All data were collected during the patients' final 24h in the intensive care unit. There was a significant difference between day and night patient activity within but not between conditions. Heart rates differed between day and night significantly for patients in the ordinary room but not in the intervention room or between conditions. Body temperature was lowest at night for all patients with no significant difference between conditions. Patients in both conditions had a natural circadian rhythm; and the cycled lighting intervention showed no significant impact. As the sample size was small, a larger repeated measures study should be conducted to determine if other types of lighting or environmental factors can impact patients' well-being.

Effects of Handling and Environment on Preterm Newborns Sleeping in Incubators

OBJECTIVE

To describe the total sleep time, stages of sleep, and wakefulness of preterm newborns and correlate them to levels of sound pressure, light, temperature, relative air humidity, and handling inside incubators.

DESIGN

Observational, correlational study.

SETTING

A neonatal intermediate care unit.

PARTICIPANTS

Twelve preterm newborns, who were 32.2 ± 4.2 weeks gestational age and weighed 1,606 ± 317 g.

METHODS

Sleep records were assessed by polysomnograph. Environmental variables were measured with a noise dosimeter, light meter, and thermohygrometer. To record time and frequency of handling, a video camera was used. All recordings were made for an uninterrupted 24-hour period.

RESULTS

Mean total sleep time in 24 hours was 899 ± 71.8 minutes (daytime = 446 ± 45.3 and nighttime = 448 ± 60.2). Mean wakefulness was 552 ± 94.0 minutes. The predominant stage was quiet sleep. A significant correlation was identified only between the levels of light and wakefulness (r = 0.65 and p = .041).

CONCLUSION

The environmental conditions and care provided to hospitalized preterm newborns did not influence sleep except for high light levels, which increased wakefulness. Nurses in clinical practice should implement strategies to promote and protect sleep by decreasing newborns' exposure to excessive light.

The NICU Lighted Environment

Lighting technologies are rapidly evolving, creating many opportunities for good lighting within the NICU. With the widespread adoption of advanced solid-state lighting technologies, lighting no longer needs to be static. Rather, lighting systems can be more easily adjusted to the different and changing visual and non-visual needs of the professional staff, infants and family members throughout the 24-hour day. This paper provides a conceptual framework for defining good lighting in the NICU, recognizing the needs of various constituent groups, each with very different needs from the lighting. Several other papers on the topic of lighting for various constituent groups at different times of the day in the NICU are summarized. Attention is given specifically to the Recommended Standards for Newborn ICU Design, a consensus standard developed by a wide range of experts, to help the reader translate this conceptual framework to practice.

Cycled light in the intensive care unit for preterm and low birth weight infants

BACKGROUND

Potential benefits and harms of different lighting in neonatal units have not been quantified.

OBJECTIVES

• To determine effectiveness and safety of cycled light (CL) (approximately 12 hours of light on and 12 hours of light off) for growth in preterm infants at three and six months' corrected age (CA).• In separate analyses, to compare effects of CL with those of irregularly dimmed light (DL) or near darkness (ND), and effects of CL with those of continuous bright light (CBL), on growth in preterm infants at three and six months' CA.• To assess, in subgroup analyses, the effectiveness and safety of CL (vs control interventions (DL, ND and CBL)) introduced at different postmenstrual ages (PMAs) - before 32 weeks', at 32 weeks' and from 36 weeks' PMA - and to compare effectiveness and safety of CL for small for gestational age (GA) infants versus appropriately grown infants.

SEARCH METHODS

We used the standard search strategy of the Cochrane Neonatal Review Group to search the Cochrane Central Register of Controlled Trials (CENTRAL; 2016, Issue 12), MEDLINE via PubMed (1966 to January 2016), Embase (1980 to January 2016) and the Cumulative Index to Nursing and Allied Health Literature (CINAHL; 1982 to January 2016). We searched clinical trials databases, conference proceedings and reference lists of retrieved articles for randomised controlled trials and quasi-randomised trials.

SELECTION CRITERIA

Randomised or quasi-randomised trials of CL versus ND or CBL in preterm and low birth weight infants.

DATA COLLECTION AND ANALYSIS

We performed data collection and analyses according to the methods of the Cochrane Neonatal Review Group. We used the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach to assess the quality of evidence.

MAIN RESULTS

We identified one additional study enrolling 38 participants for inclusion in this update, for a total of nine studies reporting on 544 infants. In general, the quality of the studies was low, mainly owing to lack of blinding and small sample sizes.Six studies enrolling 424 infants compared CL versus ND. No study reported on weight at three or six months. One study (n = 40) found no statistically significant difference in weight at four months between CL and ND groups. In another study (n = 62), the ratio of day-night activity before discharge favoured the CL group (mean difference (MD) 0.18, 95% confidence interval (CI) 0.17 to 0.19), indicating 18% more activity during the day than during the night in the CL group compared with the ND group. Two studies (n = 189) reported on retinopathy of prematurity (stage ≥ 3) and reported no statistically significant differences between CL and ND groups (typical risk ratio (RR) 0.53, 95% CI 0.25 to 1.11, I(2) = 0%; typical risk difference (RD) -0.09, 95% CI -0.19 to 0.01, I(2) = 0%). Two studies (n = 77) reported length of hospital stay (days) and noted a significant reduction in length of stay between CL and ND groups favouring the CL group (weighted mean difference (WMD) -13 days, 95% CI -23 to -2, I(2) = 0%; no heterogeneity). The quality of the evidence according to GRADE was low for this outcome. One study (n = 37) reported less crying at 11 weeks' corrected age (CA) in the CL group compared with the ND group (MD -0.57 hours/24 h, 95% CI -1.09 to -0.05). Tests for heterogeneity were not applicable.Three studies enrolling 120 infants compared CL versus CBL. Two studies (n = 79) reported significantly shorter length of stay in the CL group compared with the CBL group (WMD -16.5 days, 95% CI -26.2 to -6.8, I(2) = 0%; no heterogeneity). The quality of the evidence according to GRADE was low for this outcome. One study (n = 41) reported higher mean weight at three months' CA among infants cared for in the CL nursery (P value < 0.02) and a lower mean number of hours spent awake in 24 hours at three months of age (P value < 0.005). Data could not be entered into RevMan or GRADE. One study (n = 41) reported shorter time on the ventilator in the CL compared with the CBL group (MD -18.2 days, 95% CI -31.40 to -5.0). One study (n = 41) reported a shorter time to first oral feeding in the CL group (MD -6.8 days, 95% CI -13.29 to -0.31). We identified no safety issues.

AUTHORS' CONCLUSIONS

Trials assessing the effects of CL have enrolled 544 infants. No study reported on our primary outcome of weight at three or six months. Results from one additional study strengthen our findings that CL versus CBL shortens length of stay, as does CL versus ND. The quality of the evidence on both comparisons for this outcome according to GRADE was low. Future research should focus on comparing CL versus ND.

Influence of light exposure at nighttime on sleep development and body growth of preterm infants

Previous studies have demonstrated that a light-dark cycle has promoted better sleep development and weight gain in preterm infants than constant light or constant darkness. However, it was unknown whether brief light exposure at night for medical treatment and nursing care would compromise the benefits brought about by such a light-dark cycle. To examine such possibility, we developed a special red LED light with a wavelength of >675 nm which preterm infants cannot perceive. Preterm infants born at <36 weeks’ gestational age were randomly assigned for periodic exposure to either white or red LED light at night in a light-dark cycle after transfer from the Neonatal Intensive Care Unit to the Growing Care Unit, used for supporting infants as they mature. Activity, nighttime crying and body weight were continuously monitored from enrolment until discharge. No significant difference in rest-activity patterns, nighttime crying, or weight gain was observed between control and experimental groups. The data indicate that nursing care conducted at 3 to 4-hour intervals exposing infants to light for <15 minutes does not prevent the infants from developing circadian rest-activity patterns, or proper body growth as long as the infants are exposed to regular light-dark cycles.

Light and maternal influence in the entrainment of activity circadian rhythm in infants 4-12 weeks of age

The influence of light and maternal activity on early infant activity rhythm were studied in 43 healthy, maternal-infant pairs. Aims included description of infant and maternal circadian rhythm of environmental light, assessing relations among of activity and light circadian rhythm parameters, and exploring the influence of light on infant activity independent of maternal activity. Three-day light and activity records were obtained using actigraphy monitors at infant ages 4, 8, and 12 weeks. Circadian rhythm timing, amplitude, 24-hour fit, rhythm center, and regularity were determined using cosinor and nonparametric circadian rhythm analyses (NPCRA). All maternal and infant circadian parameters for light were highly correlated. When maternal activity was controlled, the partial correlations between infant activity and light rhythm timing, amplitude, 24-hour fit, and rhythm center demonstrated significant relation (r = .338 to .662) at infant age 12 weeks, suggesting entrainment. In contrast, when maternal light was controlled there was significant relation between maternal and infant activity rhythm (r = 0.470, 0.500, and 0.638 at 4, 8 and 12 weeks, respectively) suggesting the influence of maternal-infant interaction independent of photo entrainment of cycle timing over the first 12 weeks of life. Both light and maternal activity may offer avenues for shaping infant activity rhythm during early infancy.

Nocturnal light pollution and underexposure to daytime sunlight: Complementary mechanisms of circadian disruption and related diseases

Routine exposure to artificial light at night (ALAN) in work, home, and community settings is linked with increased risk of breast and prostate cancer (BC, PC) in normally sighted women and men, the hypothesized biological rhythm mechanisms being frequent nocturnal melatonin synthesis suppression, circadian time structure (CTS) desynchronization, and sleep/wake cycle disruption with sleep deprivation. ALAN-induced perturbation of the CTS melatonin synchronizer signal is communicated maternally at the very onset of life and after birth via breast or artificial formula feedings. Nighttime use of personal computers, mobile phones, electronic tablets, televisions, and the like--now epidemic in adolescents and adults and highly prevalent in pre-school and school-aged children--is a new source of ALAN. However, ALAN exposure occurs concomitantly with almost complete absence of daytime sunlight, whose blue-violet (446-484 nm λ) spectrum synchronizes the CTS and whose UV-B (290-315 nm λ) spectrum stimulates vitamin D synthesis. Under natural conditions and clear skies, day/night and annual cycles of UV-B irradiation drive corresponding periodicities in vitamin D synthesis and numerous bioprocesses regulated by active metabolites augment and strengthen the biological time structure. Vitamin D insufficiency and deficiency are widespread in children and adults in developed and developing countries as a consequence of inadequate sunlight exposure. Past epidemiologic studies have focused either on exposure to too little daytime UV-B or too much ALAN, respectively, on vitamin D deficiency/insufficiency or melatonin suppression in relation to risk of cancer and other, e.g., psychiatric, hypertensive, cardiac, and vascular, so-called, diseases of civilization. The observed elevated incidence of medical conditions the two are alleged to influence through many complementary bioprocesses of cells, tissues, and organs led us to examine effects of the totality of the artificial light environment in which humans reside today. Never have chronobiologic or epidemiologic investigations comprehensively researched the potentially deleterious consequences of the combination of suppressed vitamin D plus melatonin synthesis due to life in today's man-made artificial light environment, which in our opinion is long overdue.

Influence of light exposure during early life on the age of onset of bipolar disorder

BACKGROUND

Environmental conditions early in life may imprint the circadian system and influence response to environmental signals later in life. We previously determined that a large springtime increase in solar insolation at the onset location was associated with a younger age of onset of bipolar disorder, especially with a family history of mood disorders. This study investigated whether the hours of daylight at the birth location affected this association.

METHODS

Data collected previously at 36 collection sites from 23 countries were available for 3896 patients with bipolar I disorder, born between latitudes of 1.4 N and 70.7 N, and 1.2 S and 41.3 S. Hours of daylight variables for the birth location were added to a base model to assess the relation between the age of onset and solar insolation.

RESULTS

More hours of daylight at the birth location during early life was associated with an older age of onset, suggesting reduced vulnerability to the future circadian challenge of the springtime increase in solar insolation at the onset location. Addition of the minimum of the average monthly hours of daylight during the first 3 months of life improved the base model, with a significant positive relationship to age of onset. Coefficients for all other variables remained stable, significant and consistent with the base model.

CONCLUSIONS

Light exposure during early life may have important consequences for those who are susceptible to bipolar disorder, especially at latitudes with little natural light in winter. This study indirectly supports the concept that early life exposure to light may affect the long term adaptability to respond to a circadian challenge later in life.

Very preterm infants show earlier emergence of 24-hour sleep-wake rhythms compared to term infants

BACKGROUND

Previous studies show contradictory results about the emergence of 24-h rhythms and the influence of external time cues on sleep-wake behavior in preterm compared to term infants.

AIMS

To examine whether very preterm infants (<32 weeks of gestational age) differ in their emergence of the 24-h sleep-wake rhythm at 5, 11 and 25 weeks corrected age compared to term infants and whether cycled light conditions during neonatal intermediate care affects postnatal 24-h sleep-wake rhythms in preterm infants.

STUDY DESIGN

Prospective cohort study with nested interventional trial.

SUBJECTS

34 preterm and 14 control term infants were studied. During neonatal hospitalization, preterm infants were randomly assigned to cycled light [7 am-7 pm lights on, 7 pm-7 am lights off, n=17] or dim light condition [lights off whenever the child is asleep, n=17].

OUTCOME MEASURES

Sleep and activity behavior recorded by parental diary and actigraphy at 5, 11 and 25 weeks corrected age.

RESULTS

Sleep at nighttime and the longest consolidated sleep period between 12 pm-6 am was longer (mixed model analysis, factor group: p=0.02, resp. p=0.01) and activity at nighttime was lower (p=0.005) at all ages in preterm compared to term infants. Cycled light exposed preterm infants showed the longest nighttime sleep duration. Dim light exposed preterm infants were the least active.

CONCLUSIONS

Preterm infants show an earlier emergence of the 24-h sleep-wake rhythm compared to term infants. Thus, the length of exposure to external time cues such as light may be important for the maturation of infant sleep-wake rhythms. Trial registry number: This trial has been registered at www.clinicaltrials.gov (identifier NCT01513226).

Getting rhythm: how do babies do it?

OBJECTIVES

To investigate the emergence of biological rhythms in the first months of life in human infants, by measuring age-related changes in core body temperature during night-time sleep, hormones (cortisol and 6-sulfatoxymelatonin) and the expression of a clock-controlled gene H3f3b in oral epithelial cells.

DESIGN

Observational longitudinal study.

SETTING

We measured overnight core body temperature, actigraphy, day-night urinary cortisol and 6-sulfatoxymelatonin, as well as circadian gene expression, in infants at home from March 2007 to July 2008 in Leicester.

PARTICIPANTS

We recruited 35 healthy Caucasian infants who were born at term. They were monitored from 6 to 18 weeks of age.

RESULTS

At 8 weeks of age the day-night rhythm of cortisol secretion was the first to appear followed by 6-sulfatoxymelatonin 1 week later; at the same time that night-time sleep was established. At 10 weeks, the maximum fall in deep body temperature occurred with the onset of night-time sleep, followed at 11 weeks by the rhythmical expression of the H3f3b gene.

CONCLUSIONS

In human infants, there is a clear sequential pattern for the emergence of diurnal biological rhythms between 6 and 18 weeks of postnatal age, led by the secretion of cortisol and linked with the establishment of consolidated night-time sleep. It is likely that this represents part of a maturation and adaption process as infants gain equilibrium with their external environment after birth.

A light/dark cycle in the NICU accelerates body weight gain and shortens time to discharge in preterm infants

BACKGROUND

Bright constant light levels in the NICU may have negative effects on the growth and development of preterm infants

OBJECTIVE

The aim of this study is to evaluate the benefits of an alternating light/dark cycle in the NICU on weight gain and early discharge from the therapy in premature infants.

PATIENTS AND METHODS

A randomized interventional study was designed comparing infants in the NICU of Hospital Juarez de México, exposed from birth either to an LD environment (LD, n=19) or to the traditional continuous light (LL, n=19). The LD condition was achieved by placing individual removable helmets over the infant's heads. Body weight gain was analyzed, as the main indicator of stability and the main criteria for discharge in preterm infants born at 31.73±0.31week gestational age.

RESULTS

Infants maintained in an LD cycle gained weight faster than infants in LL and therefore attained a shorter hospital stay, (34.37±3.12 vs 51.11±5.29days; P>0.01). Also, LD infants exhibited improved oxygen saturation and developed a daily melatonin rhythm.

CONCLUSIONS

These findings provide a convenient alternative for establishing an LD environment for preterm healthy newborns in the NICU and confirm the beneficial effects of an alternating LD cycle for growth and weight gain and for earlier discharge time. Here we provide an easy and practical alternative to implement light/dark conditions in the NICU.

Influence of acoustic stimulation on the circadian and ultradian rhythm of premature infants

The aim of the present study was to evaluate the development of the circadian rhythm of the salivary cortisol in premature infants and its correlation with the onset of the sleep-activity behavior pattern during the first 3 weeks of life under controlled light:dark conditions. Furthermore, we investigated the influence of acoustic stimulation by audiotaped lullabies or the maternal voice on the cortisol values and long-term sleep-activity patterns. The study was a block-randomized, prospective clinical trial with a study population of 62 preterm neonates (30<37 gestational age). We compared two study groups who listened either to music or to the maternal voice (music: N=20; maternal voice: N=20) with a matched control group (N=22). The acoustic stimulation took place every evening between 20:00 and 21:00 h for 30 min over a period of 2 weeks. The cortisol values and activity-rest behavior of the neonates were determined during the first 3 weeks of life on the 1st, 7th and 14th day. Actigraphic monitoring was used to record the activity pattern continuously over 24 h and a validated algorithm for neonates was used to estimate sleep and wakefulness. The saliva samples were obtained 10 min before and 10 min after the acoustic interventions for the study groups. Additionally, saliva samples were obtained from the control group seven times over a 24-h period (20:00, 21:00, 01:00, 05:00, 08:00, 13:00 and 17:00 h). The cortisol data were analyzed by fast Fourier transformation to assess periodic characteristics and frequencies. Hierarchical linear modeling was further performed for the statistical analysis.

RESULTS

The cortisol rhythm analysis indicated a circadian rhythm pattern for only one premature infant, all others of the neonates showed no circadian or ultradian rhythm in cortisol. Cortisol level of the premature neonates was significantly higher during the first day of the study period at night-time (median: 17.1 nmol/L, IQR=9.7-24.4 nmol/L) than on days 7 (median: 9.6 nmol/L, IQR=4.7-14.6 nmol/L; Tukey-HSD, z=4.12, p<0.001) and 14 (IQR=5.8-13.7 nmol/L; Tukey-HSD, z=2.89, p<0.05). No significant effect of acoustic stimulation was observed on the cortisol concentration and sleep-wake behavior. The activity-sleep rhythm of preterm neonates was dominated by ultradian rhythm patterns with a prominent period length of 4 h (30.5%). Activity frequencies of neonates were also significantly higher overnight on the first study day (mean: 329±185.1 U) than of night seven (mean: 260.2±132.4 U; Tukey-HSD, z=2.50, p<0.05). Quiet-activity patterns increased, whereas high-activity patterns decreased during the observation period. Average sleep time increased significantly during the study time from day 1 to day 7 (Tukey-HSD, z=2.51, p<0.05). In conclusion, premature infants showed higher cortisol levels - without a circadian rhythmicity - and higher activity frequencies in the first days after birth which may reflect an adaptation process of neonates after birth. Cortisol concentrations and the activity patterns were not influenced by music interventions.

On the role of exponential smoothing in circadian dosimetry

The effects lighting has on health through modulation of circadian rhythms are becoming increasingly well documented. Data are still needed to show how light exposures are influenced by architecture and lighting design and circadian dosimetry analyses should provide duration, phase and amplitude measures of 24 h exposure profiles. Exponential smoothing is used to derive suitable metrics from 24 h light measurements collected from private dwellings. A further application of these modified exposure time series as physiological models of the light drive is discussed. Unlike previous light drive models, the dose rate persists into periods of darkness following exposures. Comparisons to long duration exposure studies suggest this type of persistent light drive model could be incorporated into contemporary physiological models of the human circadian oscillator.