Circadian and sleep development in preterm infants occurs independently from the influences of environmental lighting

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

BACKGROUND, AIMS

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

MATERIALS AND METHODS

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

RESULTS

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

CONCLUSIONS

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

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.

Qualitative study of the association between psychosocial health and physical activity/sleep quality in toddlers

Physical activity and sleep are important factors of mental and physical health in children, with some reports indicating that their effects can persist into adulthood. However, there is limited research on the qualitative aspects of physical activity and sleep in preschool children, particularly in those aged < 3 years. Therefore, to elucidate the association between psychosocial health and physical activity/sleep in early childhood in terms of qualitative aspects, we conducted a retrospective cohort study in 2985 3-year-old children (37.2 ± 0.75 months) in Shanghai, China. An analysis using structural equation modeling indicated that current physical activity had a direct and moderate impact on current psychosocial health evaluated using the Strength and Difficulties Questionnaire. In particular, past physical activity had an indirect and mild effect on current psychosocial health via current physical activity in girls. However, regardless of sex, past sleep quality had slight impact on current psychosocial health, not only indirectly via current sleep quality, but also directly. These findings highlight the importance of considering the qualitative aspects of physical activity and sleep quality as significant factors influencing the current and future psychosocial health of children, even at a very early age (< 3 years).

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.

Sleep from Infancy Through Adolescence

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

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.

Effect of a light-darkness cycle on the body weight gain of preterm infants admitted to the neonatal intensive care unit

The Continuous bright light conditions to which premature infants are subjected while hospitalized in Neonatal Intensive Care Units (NICU) can have deleterious effects in terms of growth and development. This study evaluates the benefits of a light/darkness cycle (LDC) in weight and early hospital discharge from the NICU. Subjects were recruited from three participating institutions in Mexico. Eligible patients (n = 294) were premature infants who were hospitalized in the low-risk and high-risk neonatal units classified as stable. The subjects randomized to the experimental group (n = 150) were allocated to LDC conditions are as follows: light from 07:00 to 19:00 and darkness (25 lx) from 19:00 to 07:00. The control group (n = 144) was kept under normal room light conditions (CBL) 24 h a day. Main outcome was weight gain and the effect of reducing the intensity of nocturnal light in development of premature infants. Infants to the LDC gained weight earlier, compared with those randomized to CBL, and had a significant reduction in length of hospital stay. These results highlight those premature infants subjected to a LDC exhibit improvements in physiological development, favoring earlier weight gain and consequently a decrease in hospital stays. ClinicalTrials.gov; 02/09/2020 ID: NCT05230706.

Effect of non-pharmacological interventions on sleep in preterm infants in the neonatal intensive care unit: A protocol for systematic review and network meta-analysis

BACKGROUND

Premature infants are prone to suffer multisystem complications after birth due to the incomplete development of organ tissues and low immunity, and they require a longer period of supervised treatment in the neonatal intensive care unit (NICU). However, due to the specificity of medical care in the NICU, the sleep of preterm infants is highly susceptible that has an impact on the prognosis of preterm infants. Recently, various non-pharmacological interventions have been applied to the sleep of preterm infants in the NICU, which have shown positive outcomes. However, the efficacy and safety of them are unclear. This study aims to evaluate the effects of non-pharmacological interventions on sleep in preterm infants in the NICU through a network meta-analysis.

METHODS

Randomized controlled trials of non-pharmacological interventions on sleep in preterm infants in the NICU published before September 2021 will be searched in online databases, including the Chinese Scientific Journal Database, China National Knowledge Infrastructure Database, Wanfang, China Biomedical Literature Database, PubMed, Cochrane Library, Embase, and Web of Science. Two researchers will be independently responsible for screening and selecting eligible literatures, extracting data and evaluating the risk of bias in the included studies. Stata 14.0 software will be used for data analysis.

RESULTS

The results of this meta-analysis will be submitted to a peer-reviewed journal for publication.

CONCLUSION

This study will provide comprehensive and reliable evidence-based references for the efficacy and safety in different non-pharmacological interventions on sleep in preterm infants in the NICU.

Cycled Lighting Versus Continuous Near Darkness in Preterm Infants: A Randomized Controlled Trial

OBJECTIVE

To compare the effectiveness of cycled lighting (CL) or continuous near darkness (CND) on weight in preterm infants.

STUDY DESIGN

Total 147 infants with a gestational age 25-32 weeks and/or a birth weight 750-1500 g were included in the study. The infants were classified into two groups: CL and CND. Weight on postnatal day 14, weight at corrected 35 weeks, mean rectal temperature and serum growth hormone, cortisol, melatonin levels at 35 weeks' post menstrual age (PMA), weekly weight gain, full enteral feeding time, duration of mechanical ventilation, retinopathy of prematurity (ROP), length of stay in the hospital, weight and length at three and six months corrected age were compared between the groups.

RESULTS

There were no differences between weights on postnatal day 14. Anthropometric parameters and mean rectal temperatures of groups also were not different at 35 weeks' PMA. There were no differences among the groups in duration of full enteral feeding time, length of stay in hospitalization, duration of mechanical ventilation, ROP and anthropometric parameters. Further, serum growth hormone, cortisol, and melatonin levels were similar between the groups at 35 weeks' PMA.

CONCLUSION

CL and CND did not have any advantages over each other.

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.

Influence of Intensive Care Unit Enlightenment on Premature Infants on Functional Brain Maturation Assessed by Amplitude-Integrated Electroencephalograph

OBJECTIVE

Amplitude-integrated electroencephalograph (aEEG) presents a valuable tool for functional brain maturation of preterm infants. However, the effect of enlightenment on functional brain maturation of premature infants has not been investigated. We aimed to do this with aEEG.

STUDY DESIGN

A total of 32 infants, 30 to 35 gestational weeks, were involved in the study. They were randomly distributed into three groups in which different lighting protocols were applied. In group 1, the infants' incubators were covered for 24 hours. In group 2, the infants' incubators were open for 24 hours. In group 3, the infants' incubators were covered for 12 hours and open for another 12 hours. The infants are evaluated with aEEG recordings done on the 3rd (first measurement) and 10th days (second measurement) along with the Burdjalov scoring. Analysis of aEEG recordings was performed, based on sleep-wake cycles (SWCs), upper and lower margin amplitudes, narrowband and broadband of SWC, and bandwidth of SWC.

RESULTS

At first, the narrowband lower amplitudes in group 1 were higher than those of the other groups (p = 0.042), but the difference was not significant in the second measurement (p = 0.110). The Burdjalov scores were higher in group 1 and group 3 on 10th day, though not statistically significant (p = 0.871). When the infants were re-evaluated according to the gestational weeks, the Burdjalov scores of the two groups less than 34 weeks (30-31 and 32-33 weeks) were similar, whereas 34 to 35 weeks were higher when compared with those of the two groups.

CONCLUSION

The difference observed between groups in terms of narrowband lower amplitude in the first measurement may reflect the effect of intrauterine environment rather than enlightenment at the same gestational age because it was made on the third day. However, the fact that all groups have similar results on day 10 suggests that other factors in the intensive care setting may diminish the effect of enlightenment. Burdjalov scores are associated with maturation, and high scores found in the 34- to 35-week group suggest that the 34-week maturation might be a threshold for SWC and development in our group sample.

Growth and Behavior of Congenitally Anophthalmic Lee-Sung Pigs

Circadian rhythm is usually regulated by the environmental light-dark cycle. Congenitally anophthalmic miniature pigs provide a valuable model for the study of factors affecting circadian rhythms in the absence of visual exposure to the light-dark cycle. This study investigated the growth and daily behavior patterns of Lee-Sung pigs with congenital anophthalmia. Growth in 5 Lee-Sung pigs (LSP) with congenital anophthalmia (LSP-A) and 10 normally developed pigs (LSP-N) was assessed when they were 1 through 6 mo old. Behavioral studies using digital video recording were completed in 6 sexually mature LSP (3 LSP-A and 3 LSP-N). MRI showed that LSP-A lose their vision because of a lack of retinal input and optic chiasm development. LSP-N and LSP-A did not differ in body weight or size at 2, 4, and 6 mo of age. Behavior and activity pattern studies showed that both LSP-A and LSP-N were active mainly during daylight, but LSP-A spent significantly more time exploring their environment during the day (28%) and night (10%) than did LSP-N. This study revealed that growth performance was similar between LSP-A and normal pigs, but their behavior and activity patterns differed. LSP-A showed circadian rhythm abnormalities similar to those in blind humans. This study provides basic data on LSP-A as a model for studying compensatory cross-modal brain plasticity and hormone regulation in the absence of retinal input is deficient and for understanding the role of circadian rhythm regulation.

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.

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.

Infant sleep and its relation with cognition and growth: a narrative review

OBJECTIVE

Infant sleep development is a highly dynamic process occurring in parallel to and in interaction with cognitive and physical growth. This narrative review aims to summarize and discuss recent literature and provide an overview of the relation between infant sleep and cognitive development as well as physical growth.

METHODS

We conducted online literature search using MEDLINE, Embase, and Cochrane Library databases. We considered original research on humans published in the English language from January 2005 to December 2015. Search terms included "sleep" AND "infant" AND "cognition" OR "memory" OR "executive functioning", OR "growth" OR "obesity" OR "growth hormone" OR "stunting", and combinations thereof.

RESULTS

Ten studies on infant sleep and cognition were included in this review. Overall, findings indicated a positive association between sleep, memory, language, executive function, and overall cognitive development in typically developing infants and young children. An additional 20 studies support the positive role of infant sleep in physical growth, with the current literature focusing largely on weight gain and obesity rather than healthy growth. Existing evidence in both the domains is mainly based on cross-sectional designs, on association studies, and on parental reports. In contrast, there were limited studies on longitudinal sleep trajectories and intervention effects, or studies have not used more objective sleep measures such as actigraphy and polysomnography.

CONCLUSION

The reviewed studies support a critical and positive role of infant sleep in cognition and physical growth. Future studies should consider key environmental and parental confounders, include a combination of more objective (actigraphy) and subjective measures (sleep diaries and questionnaires), and move towards longitudinal trajectory designs of infant sleep and development.

Dynamics and complexity of body temperature in preterm infants nursed in incubators

BACKGROUND

Poor control of body temperature is associated with mortality and major morbidity in preterm infants. We aimed to quantify its dynamics and complexity to evaluate whether indices from fluctuation analyses of temperature time series obtained within the first five days of life are associated with gestational age (GA) and body size at birth, and presence and severity of typical comorbidities of preterm birth.

METHODS

We recorded 3h-time series of body temperature using a skin electrode in incubator-nursed preterm infants. We calculated mean and coefficient of variation of body temperature, scaling exponent alpha (Talpha) derived from detrended fluctuation analysis, and sample entropy (TSampEn) of temperature fluctuations. Data were analysed by multilevel multivariable linear regression.

RESULTS

Data of satisfactory technical quality were obtained from 285/357 measurements (80%) in 73/90 infants (81%) with a mean (range) GA of 30.1 (24.0-34.0) weeks. We found a positive association of Talpha with increasing levels of respiratory support after adjusting for GA and birth weight z-score (p<0.001; R2 = 0.38).

CONCLUSION

Dynamics and complexity of body temperature in incubator-nursed preterm infants show considerable associations with GA and respiratory morbidity. Talpha may be a useful marker of autonomic maturity and severity of disease in preterm infants.

Vibrotactile stimulation: A non-pharmacological intervention for opioid-exposed newborns

Objective

To examine the therapeutic potential of stochastic vibrotactile stimulation (SVS) as a complementary non-pharmacological intervention for withdrawal in opioid-exposed newborns.

Study design

A prospective, within-subjects single-center study was conducted in 26 opioid-exposed newborns (>37 weeks; 16 male) hospitalized since birth and treated pharmacologically for Neonatal Abstinence Syndrome. A specially-constructed mattress delivered low-level SVS (30-60Hz, 10–12μm RMS), alternated in 30-min intervals between continuous vibration (ON) and no vibration (OFF) over a 6–8 hr session. Movement activity, heart rate, respiratory rate, axillary temperature and blood-oxygen saturation were calculated separately for ON and OFF.

Results

There was a 35% reduction in movement activity with SVS (p<0.001), with significantly fewer movement periods >30 sec duration for ON than OFF (p = 0.003). Incidents of tachypneic breaths and tachycardic heart beats were each significantly reduced with SVS, whereas incidents of eupneic breaths and eucardic heart beats each significantly increased with SVS (p<0.03). Infants maintained body temperature and arterial-blood oxygen level independent of stimulation condition.

Conclusions

SVS reduced hyperirritability and pathophysiological instabilities commonly observed in pharmacologically-managed opioid-exposed newborns. SVS may provide an effective complementary therapeutic intervention for improving autonomic function in newborns with Neonatal Abstinence Syndrome.

Environmental factors influencing biological rhythms in newborns: From neonatal intensive care units to home

Photic and non-photic environmental factors are suggested to modulate the development of circadian rhythms in infants. Our aim is to evaluate the development of biological rhythms (circadian or ultradian) in newborns in transition from Neonatal Intensive Care Units (NICU) to home and along the first 6 months of life, to identify masking and entraining environment factors along development. Ten newborns were evaluated in their last week inside the NICU and in the first week after being delivered home; 6 babies were also followed until 6 months of corrected age. Activity, recorded with actimeters, wrist temperature and observed sleep and feeding behavior were recorded continuously along their last week inside the NICU and in the first week at home and also until 6 months of corrected age for the subjects who remained in the study. Sleep/wake and activity/rest cycle showed ultradian patterns and the sleep/wake was strongly influenced by the 3 h feeding schedule inside the NICU, while wrist temperature showed a circadian pattern that seemed no to be affected by environmental cycles. A circadian rhythm emerges for sleep/wake behavior in the first week at home, whereas the 3 h period vanishes. Both activity/rest and wrist temperature presented a sudden increase in the contribution of the circadian component immediately after babies were delivered home, also suggesting a masking effect of the NICU environment. We found a positive correlation of postconceptional age and the increase in the daily component of activity and temperature along the following 6 months, while feeding behavior became arrhythmic.

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.

Development of sleep/wake, activity and temperature rhythms in newborns maintained in a neonatal intensive care unit and the impact of feeding schedules

Biological rhythms in infants are described as evolving from an ultradian to a circadian pattern along the first months of life. Recently, the use of actigraphy and thermistors with memory has contributed to the understanding of temporal relations of different variables along development. The aim of this study was to describe and compare the development of the rhythmic pattern of wrist temperature, activity/rest cycle, sleep/wake and feeding behavior in term and preterm newborns maintained in a neonatal intensive care unit (NICU).

METHODS

Nineteen healthy preterm and seven fullterm newborns had the following variables monitored continuously while they were in the NICU: activity recorded by actigraphy, wrist temperature recorded with a thermistor and observed sleep and feeding behavior recorded by the NICU staff with diaries. Subjects were divided in 3 groups according to their gestational age at birth and rhythmic parameters were compared.

RESULTS

A dominant daily rhythm was observed for wrist temperature since the first two weeks of life and no age relation was demonstrated. Otherwise, a daily pattern in activity/rest cycle was observed for most preterm newborns since 35 weeks of postconceptional age and was more robust in term babies. Feeding and sleep/wake data showed an almost exclusive 3h rhythm, probably related to a masking effect of feeding schedules.

CONCLUSIONS

We found that wrist temperature develops a daily pattern as soon as previously reported for rectal temperature, and with acrophase profile similar to adults. Moreover, we were able to find a daily rhythm in activity/rest cycle earlier than previously reported in literature. We also suggest that sleep/wake rhythm and feeding behavior follow independent developmental courses, being more suitable to masking effects.

Neonatal Sleep Predicts Attention Orienting and Distractibility

OBJECTIVE

Children with sleep disorders tend to experience attention problems, yet little is known about the relationship between sleep and attention in early development. This prospective follow-up study investigated the longitudinal relationships between neonatal sleep, attention, and distraction in infants born preterm.

METHOD

We used actigraphy and sleep-wake diaries in the neonatal intensive care unit (NICU, N = 65), attention orienting in a visual-recognition-memory task (VRM) at age 4 months, and structured observation of attention and distractibility at age 18 months.

RESULTS

Infants with poorer neonatal sleep (n = 31) exhibited longer first gaze durations in the VRM at 4 months and longer distraction episodes at 18 months relative to neonatal controls who slept well (p < .01). Hierarchical regression models support relations between neonatal sleep and gaze behavior at 4 months and distractibility at 18 months; moreover, alterations in orienting attention at 4 months predicted the likelihood of being distracted during the second year of life.

CONCLUSION

Findings underscore the importance of early sleep-wake and attention regulation in the development of distraction in infants born preterm.

Can the Assessment of Spontaneous Oscillations by Near Infrared Spectrophotometry Predict Neurological Outcome of Preterm Infants?

The aim was to assess the correlation between cerebral autoregulation and outcome. Included were 31 preterm infants, gestational age 26 1/7 to 32 2/7 and <24 h life. Coherence between cerebral total haemoglobin (tHb) or oxygenation index (OI) measured by near-infrared spectrophotometry (NIRS) and systemic heart rate (HR) or arterial blood pressure (MAP) was calculated as a measure of autoregulation. In contrast to previous studies, low coherences in the first 24 h were significantly associated with intraventricular haemorrhage, death or abnormal neurodevelopmental outcome at 18 months or later. We suggest that our results can be explained by the concept of a multi-oscillatory-functions-order.

Let there be light and darkness: findings from a prestudy concerning cycled light in the intensive care unit environment

The present study reports findings concerning light in an intensive care unit setting presented from 3 aspects, giving a wide view. The first part is a systematic review of intervention studies concerning cycled light compared with dim light/noncycled light. The findings showed that cycled light may be beneficial to preterm infant health. Second, a lighting intervention in the intensive care unit is presented, comparing and assessing experience of this lighting environment with that of an ordinary room. Significant differences were shown in hedonic tone, favoring the intervention environment. In the third part, measured illuminance, luminance, and irradiance values achieved in the lighting intervention room and ordinary room lighting are reported.

Effects of intrauterine growth restriction on sleep and the cardiovascular system: The use of melatonin as a potential therapy?

Intrauterine growth restriction (IUGR) complicates 5-10% of pregnancies and is associated with increased risk of preterm birth, mortality and neurodevelopmental delay. The development of sleep and cardiovascular control are closely coupled and IUGR is known to alter this development. In the long-term, IUGR is associated with altered sleep and an increased risk of hypertension in adulthood. Melatonin plays an important role in the sleep-wake cycle. Experimental animal studies have shown that melatonin therapy has neuroprotective and cardioprotective effects in the IUGR fetus. Consequently, clinical trials are currently underway to assess the short and long term effects of antenatal melatonin therapy in IUGR pregnancies. Given melatonin's role in sleep regulation, this hormone could affect the developing infants' sleep-wake cycle and cardiovascular function after birth. In this review, we will 1) examine the role of melatonin as a therapy for IUGR pregnancies and the potential implications on sleep and the cardiovascular system; 2) examine the development of sleep-wake cycle in fetal and neonatal life; 3) discuss the development of cardiovascular control during sleep; 4) discuss the effect of IUGR on sleep and the cardiovascular system and 5) discuss the future implications of melatonin therapy in IUGR pregnancies.

Sleep deprivation, pain and prematurity: a review study

The aim was to describe current reports in the scientific literature on sleep in the intensive care environment and sleep deprivation associated with painful experiences in premature infant. A systematic search was conducted for studies on sleep, pain, premature birth and care of the newborn. Web of Knowledge, MEDLINE, LILACS, Cochrane Library, PubMed, EMBASE, Scopus, VHL and SciELO databases were consulted. The association between sleep deprivation and pain generates effects that are observed in the brain and the behavioral and physiological activity of preterm infants. Polysomnography in intensive care units and pain management in neonates allow comparison with the first year of life and term infants. We have found few references and evidence that neonatal care programs can influence sleep development and reduce the negative impact of the environment. This evidence is discussed from the perspective of how hospital intervention can improve the development of premature infants.

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).

Mother-infant circadian rhythm: development of individual patterns and dyadic synchrony

BACKGROUND

Mutual circadian rhythm is an early and essential component in the development of maternal-infant physiological synchrony.

AIMS

The aim of this to examine the longitudinal pattern of maternal-infant circadian rhythm and rhythm synchrony as measured by rhythm parameters.

STUDY DESIGN

In-home dyadic actigraphy monitoring at infant age 4, 8, and 12 weeks.

SUBJECTS

Forty-three healthy mother-infant pairs.

OUTCOME MEASURES

Circadian parameters derived from cosinor and non-parametric analysis including mesor, magnitude, acrophase, L5 and M10 midpoints (midpoint of lowest 5 and highest 10h of activity), amplitude, interdaily stability (IS), and intradaily variability (IV).

RESULTS

Mothers experienced early disruption of circadian rhythm, with re-establishment of rhythm over time. Significant time effects were noted in increasing maternal magnitude, amplitude, and IS and decreasing IV (p<.001). Infants demonstrated a developmental trajectory of circadian pattern with significant time effects for increasing mesor, magnitude, amplitude, L5, IS, and IV (p<.001). By 12 weeks, infant phase advancement was evidenced by mean acrophase and M10 midpoint occurring 60 and 43 min (respectively) earlier than at 4 weeks. While maternal acrophase remained consistent over time, infants became increasingly phase advanced relative to mother and mean infant acrophase at 12 weeks occurred 60 min before mother. Mother-infant synchrony was evidenced in increasing correspondence of acrophase at 12 weeks (r=0.704), L5 (r=0.453) and M10 (r=0.479) midpoints.

CONCLUSIONS

Development of mother-infant synchrony reflects shared elements of circadian rhythm.

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.

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

BACKGROUND

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

OBJECTIVES

To compare the effectiveness of cycled lighting (CL) (approximately 12 hours of light on and 12 hours of light off) with irregularly dimmed light (DL) or near darkness (ND) and with continuous bright light (CBL) on growth in preterm infants at three and six months of age.

SEARCH METHODS

We conducted electronic searches of the literature (in January 2013) of the Cochrane Central Register of Controlled Trials, Issue 12, 2012 (CENTRAL), MEDLINE, EMBASE, CINAHL and abstracts from Pediatric Academic Societies' annual meetings. We searched Controlled-trials.com and Clinicaltrials.gov for ongoing trials and abstracts from the Pediatric Academic Societies (PAS) Annual Meetings (2000 to 2013) using the Abstracts2view website on 10 May 2013.

SELECTION CRITERIA

Randomized 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.

MAIN RESULTS

Six studies enrolling 424 infants compared CL versus ND (including one additional trial identified in this update that enrolled 37 infants). No study reported on weight at three or six months. In one study (n = 40), there was no statistically significant difference in weight at four months between the CL and ND groups. In another study (n = 62), the ratio of day-night activity prior to 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). There was no statistically significant difference between the 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 on length of hospital stay (days). There was a significant reduction in the length of stay between the CL and the ND groups favouring the CL group (MD -13 days, 95% CI -2 to -23). One study (n = 37) reported on less crying at 11 weeks' corrected age (CA) in the CL group compared with the ND group (MD -0.57 hours/24 hours, 95% CI -1.09 to -0.05).There was no heterogeneity for this outcome (I(2) = 0%).Two studies enrolling 82 infants compared CL versus CBL. One study (n = 41) reported higher mean weight at three months' CA in infants cared for in the CL nursery (P value < 0.02) and lower mean number of hours spent awake in 24 hours at three months of age (P value < 0.005). One study (n = 41) reported shorter time on 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).For many outcomes, the trends favoured CL versus ND as well as CL versus CBL.We identified no safety issues.

AUTHORS' CONCLUSIONS

Trials assessing the effect of CL have enrolled 506 infants. Trends for many outcomes favoured CL compared with ND and CL compared with CBL. The studies may have lacked significance due to a lack of statistical power. Future research should focus on comparing CL to ND.

Cycled light exposure reduces fussing and crying in very preterm infants

OBJECTIVE

To examine whether cycled lighting (CL) conditions during neonatal care in very preterm infants (<32 weeks' gestational age [GA]) decrease crying and fussing behavior, improve the consolidation of sleep, and influence activity behavior at 5 and 11 weeks' postterm corrected age (CA) compared with preterm infants cared for in dim lighting (DL) conditions.

METHODS

Thirty-seven preterm infants were randomly assigned to CL (7 am-7 pm lights on, 7 pm-7 am lights off [n = 17; mean GA: 30.6 ± 0.95 weeks; 9 girls]) or DL (lights off whenever the child is asleep [n = 20; GA: 29.5 ± 2.1 weeks; 8 girls]) conditions. Sleeping, crying, and activity behavior was recorded by using parental diaries and actigraphy at 5 and 11 weeks' CA.

RESULTS

A significant reduction of fussing (59.4 minutes/24 hours [± 25.8 minutes]) and crying (31.2 minutes/24 hours [± 14.4 minutes]) behavior and a trend to higher motor activity during daytime was found in CL-exposed infants at 5 and 11 weeks' CA compared with infants cared for in DL conditions. No significant difference between groups was observed for sleep behavior at 5 and 11 weeks' CA. Infants in CL conditions showed a trend to improved daily weight gain (average: 3.6 g/d) during neonatal care compared with DL conditions.

CONCLUSIONS

CL conditions in neonatal care have beneficial effects on infant's fussing and crying behavior and growth in the first weeks of life. This study supports the introduction of CL care in clinical neonatal practice.

Daily rhythms of the sleep-wake cycle

The amount and timing of sleep and sleep architecture (sleep stages) are determined by several factors, important among which are the environment, circadian rhythms and time awake. Separating the roles played by these factors requires specific protocols, including the constant routine and altered sleep-wake schedules. Results from such protocols have led to the discovery of the factors that determine the amounts and distribution of slow wave and rapid eye movement sleep as well as to the development of models to determine the amount and timing of sleep. One successful model postulates two processes. The first is process S, which is due to sleep pressure (and increases with time awake) and is attributed to a 'sleep homeostat'. Process S reverses during slow wave sleep (when it is called process S'). The second is process C, which shows a daily rhythm that is parallel to the rhythm of core temperature. Processes S and C combine approximately additively to determine the times of sleep onset and waking. The model has proved useful in describing normal sleep in adults. Current work aims to identify the detailed nature of processes S and C. The model can also be applied to circumstances when the sleep-wake cycle is different from the norm in some way. These circumstances include: those who are poor sleepers or short sleepers; the role an individual's chronotype (a measure of how the timing of the individual's preferred sleep-wake cycle compares with the average for a population); and changes in the sleep-wake cycle with age, particularly in adolescence and aging, since individuals tend to prefer to go to sleep later during adolescence and earlier in old age. In all circumstances, the evidence that sleep times and architecture are altered and the possible causes of these changes (including altered S, S' and C processes) are examined.

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

BACKGROUND

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

OBJECTIVES

To compare the effectiveness of cycled lighting (CL) (approximately 12 hours of light on and 12 hours of light off) with irregularly dimmed light or near darkness (ND) and with continuous bright light (CBL) on growth in preterm infants at three and six months of age.

SEARCH STRATEGY

Electronic searches of the literature were conducted (in May 2010) of the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library), MEDLINE, EMBASE, CINAHL and abstracts from Pediatric Academic Societies' annual meetings.

SELECTION CRITERIA

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

DATA COLLECTION AND ANALYSIS

Data collection and analyses were performed according to the methods of the Cochrane Neonatal Review Group.

MAIN RESULTS

Five studies enrolling 387 infants compared CL to ND. No study reported on weight at three or six months. In one study (n = 40) there was no statistically significant difference in weight at four months between the CL and the ND groups. In another study (n = 62) the ratio of day-night activity prior to discharge favoured the CL group (mean difference 0.18, 95% CI 0.17 to 0.19) indicating 18% more activity during day than night in the CL group compared to the ND group. Two studies (n = 189) reported on retinopathy of prematurity (stage ≥ 3). There was no statistically significant difference between the CL and ND groups (typical RR 0.53, 95% CI 0.25 to 1.11, I(2) = 0%; typical RD -0.09, 95% CI -0.19 to 0.01, I(2) = 0%).Two studies enrolling 82 infants compared CL to CBL. One study (n = 41) reported higher mean weight at three months corrected age in infants cared for in the CL nursery (P < 0.02) and lower mean number of hours spent awake in 24 hours at three months (P < 0.005). In one study (n = 41) days on a ventilator were reduced in the CL group (mean difference -18, 95% CI -31 to -5 days).For many outcomes the trends favoured CL versus ND as well as CL versus CBL.

AUTHORS' CONCLUSIONS

Trials assessing the effect of CL have enrolled 469 infants. Trends for many outcomes favoured cycled light (CL) compared to near darkness (ND) and CL compared to continuous bright light (CBL) The studies may have lacked significance due to a lack of statistical power. Future research should focus on comparing CL to ND.

Maternal sleep-related cognitions and infant sleep: a longitudinal study from pregnancy through the 1st year

Infant sleep is a major source of concern for many parents. The aims of this longitudinal study were to assess: (a) the development of sleep patterns among infants, (b) the development of maternal cognitions regarding infant sleep, and (c) the relations between these domains during the 1st year of life. Eighty-five mothers were recruited during pregnancy and completed a questionnaire aimed at assessing maternal sleep-related cognitions. After delivery (at 1, 6, and 12 months) sleep was assessed using actigraphy and sleep logs, and maternal cognitions were reassessed. The findings demonstrated significant predictive and concomitant links between maternal cognitions and infant sleep. Maternal soothing behaviors mediated the relations between these domains.

Neurophysiologic assessment of brain maturation after an 8-week trial of skin-to-skin contact on preterm infants

OBJECTIVE

Skin-to-skin contact (SSC) promotes physiological stability and interaction between parents and infants. Analyses of EEG-sleep studies can compare functional brain maturation between SSC and non-SSC cohorts.

METHODS

Sixteen EEG-sleep studies were performed on eight preterm infants who received 8 weeks of SSC, and compared with two non-SSC cohorts at term (N=126), a preterm group corrected to term age and a full-term group. Seven linear and two complexity measures were compared (Mann-Whitney U test comparisons p<.05).

RESULTS

Fewer REMs, more quiet sleep, increased respiratory regularity, longer cycles, and less spectral beta were noted for SSC preterm infants compared with both control cohorts. Fewer REMs, greater arousals and more quiet sleep were noted for SSC infants compared with the non-SSC preterms at term. Three right hemispheric regions had greater complexity in the SSC group. Discriminant analysis showed that the SSC cohort was closer to the non-SSC full-term cohort.

CONCLUSIONS

Skin-to-skin contact accelerates brain maturation in healthy preterm infants compared with two groups without SSC.

SIGNIFICANCE

Combined use of linear and complexity analysis strategies offer complementary information regarding altered neuronal functions after developmental care interventions. Such analyses may be helpful to assess other neuroprotection strategies.

Circadian variation on oxygen consumption in preterm infants

OBJECTIVE

We investigated the diurnal variation in oxygen consumption to determine the optimal time periods of calorimetry in preterm infants.

METHODS

Oxygen consumption (VO(2)) was measured continuously for 24 h using indirect calorimetry. Twenty-two premature infants with gestational age of 27-31 (31+/-1.7) weeks were enrolled in the study. Heart rate, respiratory rate, oxygen saturation, skin and rectal temperature and physical activity were monitored continuously.

RESULTS

The averaged values of VO(2) showed a significant pattern (P<0.0001) of circadian rhythm with a peak in the afternoon and a nadir during the night with significantly differences between the mean VO(2) values. A circadian variation of VO(2) was found in more than 80% of preterm infants and was unrelated to gestational age, physical activity or environmental stress. The infants spent 90.4% of their time sleeping.

CONCLUSIONS

These findings indicate the possible existence of an endogenous circadian rhythm of VO(2) in preterm infants beginning shortly after birth. Day-night variations of VO(2) should be considered when VO(2) values are extrapolated from short measurement periods to prevent overestimation of values.

Iatrogenic environmental hazards in the neonatal intensive care unit

Premature infants in the neonatal intensive care unit (NICU) face many illnesses and complications. Another potential source of iatrogenic disease is the NICU environment. Research in this area, however, is limited.