Development of sleep-wakefulness rhythm in premature babies

The impact of sleep in high-risk infants

Most of an infant's day is devoted to sleep - and normal sleep is vital to normal brain development. Sleep disruptions may impair overall health, well-being, and neurodevelopment. Disruptors of sleep and circadian health, such as noise, light, respiratory support, and clinical interventions, are highly prevalent in hospital and nursing care facilities. These factors particularly affect infants who already have an increased risk of sleep disorders and their consequences due to an underlying disease. Preterm infants and infants with disorders such as neonatal abstinence syndrome, craniofacial malformations, congenital heart disease, hypoxic-ischemic encephalopathy, Chiari-malformation/myelomeningocele, congenital musculoskeletal disease, and Down syndrome are all at high risk for impaired development of sleep-wake cycling and for sleep-disordered breathing. Since abnormal sleep is a potentially treatable risk factor for impaired neurodevelopment, there is an urgent need for effective monitoring, timely interventions, and treatment strategies to improve sleep physiology and thereby optimize overall neurodevelopment in these high-risk populations. IMPACT: Healthy sleep plays a fundamental role in normal infant brain development. Many factors can disrupt sleep during a hospital stay. This is particularly important for infants who have an increased risk of sleep disorders due to neonatal disorders such as prematurity, congenital heart disease, or Chiari malformation. Sleep protective strategies are readily available and need to be systematically implemented into hospital care.

Comparison of two different Nasal Interfaces used in Non-Invasive Respiratory support in terms of Neonate comfort

Background

Non-Invasive Ventilation (NIV) is the first choice approach in neonates with sufficient respiratory effort that require respiratory support. The type of nasal interface used in NIV affects both efficacy and patient comfort. The aim of this study is to investigate the effects of different nasal interfaces used in NIV support on neonatal patient comfort.

Methods

Our study evaluated patients who received NIV support for 24 hours. The patients were randomly divided into two groups according to the type of nasal interface used, which were RAM cannula and short binasal prong (SBP). The patients' demographic and clinical data were noted. Their sleep was monitored for 24 hours with an actigraphy device.

Results

A total of 82 patients were evaluated. The sleep efficiency in the RAM cannula group was significantly higher (respectively, 65.7% [10.22-95.25] vs. 57.81% [2.49-77], p=0.004). Although not statistically significant, the neonates in the RAM cannula group exhibited longer total sleep time (respectively, 10.4 ± 4.28 hours vs. 9.02 ± 3.73 hours, p=0.161). Comparison of heart rates and respiratory rates indicate that the patients in the RAM cannula group were more comfortable.

Conclusions

Our study found that infants who received NIV support through a RAM cannula experienced more efficient sleep. Holistic approaches in neonatal intensive care units are vital for better neurodevelopmental outcomes in newborns. Although non-invasive, the interface used in NIV should also be a part of this holistic approach.

Sleep state organisation of moderate to late preterm infants in the neonatal unit

BACKGROUND

Sleep supports neurodevelopment and sleep architecture reflects brain maturation. This prospective observational study describes the nocturnal sleep architecture of healthy moderate to late preterm (MLP) infants in the neonatal unit at 36 weeks post menstrual age (PMA).

METHODS

MLP infants, in the neonatal unit of a tertiary hospital in Ireland from 2017 to 2018, had overnight continuous electroencephalography (cEEG) with video for a minimum 12 h at 36 weeks PMA. The total sleep time (TST) including periods of active sleep (AS), quiet sleep (QS), indeterminate sleep (IS), wakefulness and feeding were identified, annotated and quantified.

RESULTS

A total of 98 infants had cEEG with video monitoring suitable for analysis. The median (IQR) of TST in the 12 h period was 7.09 h (IQR 6.61-7.76 h), 4.58 h (3.69-5.09 h) in AS, 2.02 h (1.76-2.36 h) in QS and 0.65 h (0.48-0.89 h) in IS. The total duration of AS was significantly lower in infants born at lower GA (p = 0.007) whilst the duration of individual QS periods was significantly higher (p = 0.001).

CONCLUSION

Overnight cEEG with video at 36 weeks PMA showed that sleep state architecture is dependent on birth GA. Infants with a lower birth GA have less AS and more QS that may have implications for later neurodevelopment.

IMPACT

EEG provides objective information about the sleep organisation of the moderate to late preterm (MLP) infant. Quantitative changes in sleep states occur with each week of advancing gestational age (GA). Active sleep (AS) is the dominant sleep state that was significantly lower in infants born at lower GA. MLP infants who were exclusively fed orally had a shorter total sleep time and less AS compared to infants who were fed via nasogastric tube.

Sleep assessment in preterm infants: Use of actigraphy and aEEG

OBJECTIVE

Objective methods to monitor the sleep of preterm infants at the neonatal intensive care unit (NICU) are required to prevent potentially adverse neurodevelopmental outcomes. This study aimed to determine the concordance of actigraphy and amplitude-integrated electroencephalogram (aEEG) against gold standard direct observation (DO) in assessing sleep/wake states of typically developing preterm infants.

METHODS

This prospective observational study was conducted in a single center level III NICU. Sleep variables were measured using Philips Respironics Mini-Mitter® Actiwatch-2 for 24 h and compared with 8-h matched data of aEEG and DO. Sensitivity-specificity analysis, Cohen's kappa, prevalence-adjusted and bias-adjusted kappa (PABAK), and Bland Altman plots were generated.

RESULTS

Seventeen preterm infants were recruited. A total of 11252 epochs were studied. Sensitivity (86.4%), agreement rate (67.9%), and predictive value for wake (47.9%) for the actigraphy were highest at the automatic activity threshold whereas specificity (54.5%) and predictive value for sleep (75.5%) were highest at low threshold. The sensitivity of aEEG was 79.3% and the specificity was 54.3%. At all thresholds, the agreement was largely equivalent with low kappas (0.14-0.17) and PABAK coefficients (0.22-0.35) for actigraphy and DO. Moderate agreement was observed between aEEG and DO according to the PABAK coefficient (0.44). Mean differences in sleep parameters were not different between DO and aEEG as well as DO/aEEG and actigraphy at medium threshold (p > 0.05).

CONCLUSIONS

Actigraphy at medium threshold can be used in depicting sleep in typically developing preterm infants at NICU. aEEG may be an alternative adjunctive method to actigraphy for the evaluation of sleep/wake states in the NICU setting.

CLINICAL TRIAL REGISTRATION NUMBER

NCT04145362.

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.

Actigraphy: Metrics reveal it is not a valid tool for determining sleep in neonates

Study of emerging sleep-wake patterns in neonates is important for promptly identifying and treating abnormal sleep behaviours to ensure healthy infant development and neurobehavioral outcomes. Current methods to assess sleep are costly, labour intensive, and particularly difficult to implement in fragile, hospitalised infants requiring intensive medical care. The aim of the present study was to assess the validity of actigraphy as a tool for detecting sleep in preterm infants, using polysomnography (PSG) as the "gold standard". A total of 10 neonates (mean [SD] 35.8 [1.2] weeks post-menstrual age; five female) hospitalised since birth for prematurity each participated in one 8-10 hr session during which PSG and actigraphy were recorded simultaneously. Inter-feed minute-by-minute PSG Sleep-Wake scores were compared to concurrent actigraph epochs categorised as either "Sleep" or "Wake" using three separate movement-per-minute thresholds (≤20, ≤40, ≤80). Tool validity was assessed using five metrics. A key finding was that for each of the movement thresholds there was high agreement rate, sensitivity, and predictive value of sleep (85.2%-97.2%), whereas specificity and predictive value of wake remained low (12%-46%). Receiver operating characteristic curve analysis also revealed low discriminatory power of actigraphy for estimating sleep (area under the curve = 0.636; Youden's Index J = 0.2173). Lack of sufficient minutes of autonomous wake periods among infants was identified as a key limitation in actigraphy. Findings from the present study suggest actigraphy cannot be validated for Sleep/Wake discrimination in preterm infants and that proper validation requires sufficient data from periods of both Sleep and Wake.

Sleep patterns, problems, and ecology in young children born preterm and full-term and their mothers

BACKGROUND

Previous studies of sleep patterns and problems in preterm infants compared to full-term infants have yielded mixed results, with little known about sleep ecology. The aims of this study were to compare sleep patterns, sleep problems, and sleep ecology across developmental stages (birth to 36 months) in preterm (3 or more weeks early) infants and toddlers to those born full-term, in addition to their mothers' sleep.

METHODS

Mothers of 834 young children in Brazil (ages 0-35.9 months), half preterm and half full-term (matched for sex and chronological age), completed the Brief Infant Sleep Questionnaire and the Pittsburgh Sleep Quality Index.

RESULTS

Across the entire sample, preterm and full-term infants were similar for most sleep parameters, including sleep onset latency, number and duration of night awakenings, and sleep duration, as well as sleep ecology parameters, including falling asleep independently and sleep location. However, preterm infants were more likely to be held to initiate sleep, given a bottle to resume sleep after waking, and less likely to be breastfed to resume sleep after waking. Mothers of preterm infants, however, were more likely to report a parent-perceived sleep problem, although maternal-perceived confidence in managing child sleep and bedtime difficulty were similar. Finally, maternal sleep parameters were similar between groups.

CONCLUSIONS

Overall, these results indicate that sleep patterns, sleep problems, and sleep ecology among preterm infants and toddlers and their mothers are largely similar to those of full-term infants and toddlers and their mothers, even within the first few months.

Sleep Disturbances in Newborns

The purpose of this review is to serve as an introduction to understanding sleep in the fetus, the preterm neonate and the term neonate. Sleep appears to have numerous important roles, particularly in the consolidation of new information. The sleep cycle changes over time, neonates spend the most time in active sleep and have a progressive shortening of active sleep and lengthening of quiet sleep. Additionally, the sleep cycle is disrupted by many things including disease state and environment, and the amplitude integrated EEG can be a useful tool in evaluating sleep, and sleep disturbances, in neonates. Finally, there are protective factors for infant sleep that are still being studied.

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.

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.

Randomized controlled trial to compare sleep and wake in preterm infants less than 32weeks of gestation receiving two different modes of non-invasive respiratory support

AIM

To determine whether respiratory support via heated humidified high flow nasal cannulae (HHHFNC) results in infants <32weeks gestation spending a greater proportion of time in sleep compared to those receiving nasal continuous positive airway pressure (NCPAP).

METHODS

A subgroup of infants enrolled in a randomized controlled trial to compare HHHFNC or NCPAP post-extubation had sleep and wake activity measured by actigraphy for 72hours post-extubation. Activity diaries were completed contemporaneously to record episodes of infant handling. Actigraphy data were downloaded with known periods of handling excluded from the analysis.

RESULTS

28 infants with mean gestation of 28.3weeks (SD 2) and birth weight 1074g (SD 371) were studied. Infants receiving HHHFNC spent a lesser proportion of time in sleep 59.8% (SD 18.5) than those on NCPAP 82.2% (SD 23.8) p=0.004. Infants receiving HHHFNC had a lower sleep efficiency and higher mean activity score than those on NCPAP (p=0.003, p=0.002, respectively).

CONCLUSION

Infants receiving HHHFNC had a higher mean activity score and spent less time in sleep than those allocated NCPAP. Further study of sleep wake activity in preterm infants receiving respiratory support is required as this may impact on neurodevelopmental outcomes.

Preterm infants' orally directed behaviors and behavioral state responses to the integrated H-HOPE intervention

Preterm infants are challenged by immature infant behavioral organization which may negatively influence their ability to oral feed. The purpose of this study was to determine whether the integrated H-HOPE (Hospital to Home: Optimizing the Infant's Environment) intervention would improve infant behavioral organization by increasing the frequency of orally directed behaviors and the proportion of time spent in an alert behavioral state when offered prior to oral feeding. Mother-infant dyads (n=198) were randomly assigned to the H-HOPE intervention or the Attention Control groups. Infants were born at 29-34 weeks gestation and were clinically stable. Mothers had at least two social environmental risk factors such as minority status or less than high school education. H-HOPE is an integrated intervention that included (1) twice-daily infant directed stimulation using the ATVV intervention (auditory, tactile, visual, and vestibular stimuli) and (2) maternal participatory guidance sessions by a nurse-community advocate team. Orally directed behaviors and behavioral states were assessed weekly prior to feeding during hospitalization when infants were able to feed orally. There were no differences between the groups at baseline (Day 0, prior to the initiation of the integrated H-HOPE intervention). We observed a pattern of increased frequency of orally directed behaviors in the H-HOPE intervention group when compared to the Attention Control group, however, the proportion of time spent in an alert behavioral state remained stable in both groups over the course of the study. On Day 7, the H-HOPE intervention group exhibited a significantly higher mean frequency of orally directed behaviors than the Attention Control group (12.6 vs. 7.1 pre-intervention, 51.8 vs. 33.2 during intervention, 4.3 vs. 3.2 immediately after intervention, and 8.9 vs. 5.3 immediately prior to feeding). On Day 7, the H-HOPE intervention group exhibited a significantly higher proportion of time spent in an alert behavioral state only during intervention (0.26 vs. 0.11) and immediately after intervention (0.28 vs. 0.06). These findings are suggestive that the integrated H-HOPE intervention facilitated infant behavioral organization for clinically stable infants born between 29 and 34 weeks gestation. The orally directed behaviors appear to be an important indicator of the infant's preparation for feeding, and when used in conjunction with assessment of behavioral states, are especially valuable to the clinician. Use of this combined assessment approach in practice would strengthen clinician assessment for initiation of (beginning the first oral feeding) and daily preparation for oral feeding in preterm infants.

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.

Neurological maturation of late preterm infants at 34 wk assessed by amplitude integrated electroencephalogram

BACKGROUND

This study tested if measures of central nervous system (CNS) immaturity reflected by amplitude integrated electroencephalogram (aEEG) and associated clinical morbidities are determinants of length of hospitalization among late preterm infants born at 34 wk.

METHODS

This was a prospective cohort study of infants with a gestational age of 34 wk 0-6 d who had a single aEEG recording acquired over 6 h in a neonatal intensive care unit within 72 h of birth (n = 80). Infants were followed for predefined morbidities (classified as CNS or non-CNS) and length of hospitalization (determined by the clinical care team). aEEG variables were correlated with length of hospitalization.

RESULTS

Eighty infants were enrolled and 75 aEEG recordings were analyzed. The average length of hospitalization was 10.4 ± 7.2 d (range 3-46 d). The total number of cycles recorded in the first 72 h following birth were inversely correlated with the length of hospitalization (r(2) = 0.44, P < 0.001). Kaplan-Meier curves indicated that morbidities consistent with neurological immaturity were associated with a longer length of hospitalization (P < 0.001).

CONCLUSION

Neurological maturation as indicated by aEEG and specific clinical morbidities is an important determinant of length of hospitalization among late-preterm infants.

The development of cardiovascular and cerebral vascular control in preterm infants

Over the past three decades there has been a steady increase in the incidence of preterm birth. The worldwide rate of preterm birth is estimated to be 9.6% of all births, a total of almost 13 million births annually. Preterm birth is associated with a range of adverse cardiovascular and central nervous system outcomes, which may be attributed to altered development of these systems following preterm birth. Preterm birth has a considerable impact on cardiovascular parameters with preterm infants displaying higher heart rates and reduced blood pressure when compared to term born infants at matched ages. Furthermore, premature infants have altered autonomic control of cardiovascular parameters which manifests as abnormalities in heart rate variability and baroreflex mediated control of heart rate and blood pressure. As a result, systemic cardiovascular parameters can be unstable following preterm birth which may place stress on the neonatal brain. The brain of a preterm infant is particularly vulnerable to these fluctuations due to immature cerebral haemodynamics. Preterm infants, particularly those who are very preterm or unwell, display fluctuating pressure-passivity between systemic blood pressure and cerebral blood flow representing a considerably increased risk of cerebral haemorrhage or hypoxia. This is further compounded by immaturity of cerebral blood flow-metabolism coupling, which means increased metabolic demand cannot adequately be met by increased cerebral blood flow. It has been suggested that adverse long-term outcomes following preterm birth may occur as a result of exposure to physiological stress either in-utero or early in infancy.

Individual and gender differences matter in preterm infant state development

OBJECTIVE

To further understand state development of preterm infants throughout hospitalization and the effects of selected infant characteristics on state development.

DESIGN

Secondary data analysis of a 2-group, experimental design study.

SETTING

Two nurseries in a Northwest medical center.

PARTICIPANTS

Ninety-seven hospitalized, medically stable, preterm infants. Fifty-one subjects were females.

METHODS

Two hundred and eighty-five real-time video recordings of infants performed during 4 hour interfeeding intervals. Sleep-wake states were coded at 15 second intervals.

RESULTS

Active sleep was the dominant state across postmenstrual ages. Although not statistically significant, preterm infants showed developmental changes in state organization with increased quiet sleep, drowsy, and awake, decreased active sleep, and more defined and less diffuse states over age. A significant gender effect was found, with males having less active sleep (p=.012), more drowsy (p=.03), more awake (p=.043), less defined (p=.002), and more diffuse (p=.001) states compared with females.

CONCLUSION

The predominance of active sleep during the preterm period reflects level of brain maturation. The results emphasize individual variations in state organization influenced by endogenous and environmental factors. Gender differences are potential sources of individual variation.

Actigraphic monitoring of the activity-rest behavior of preterm and full-term infants at 20 months of age

Differences in the activity-rest behavior of preterm and full-term infants provide an important contribution to the analysis of the ontogeny of circadian rhythms. In this study, we recorded the activity-rest behavior of 17 preterm and 8 full-term infants at the approximate age of 20 months over an average of 10 days by means of actigraphic monitoring (Actiwatch, Cambridge Neurotechnology Ltd.). At the same time, the parents of the infants kept a daily diary. The activity-rest rhythm, the nighttime sleep duration, the daytime rest duration, as well as the sleep quality of the infants were analyzed. Preterm and full-term infants at the age of 20 months show a circadian rhythm with a period length between 23 h 32 min (23:32 h) and 24 h 23 min (24:23 h). It can be concluded that the preterm and full-term infants all reached a vital developmental step by showing the dominant circadian rhythm in the spectrum. The daytime rest duration of preterm infants is significantly shorter than that of full-term infants. The sleep quality of preterm infants is significantly lower than that of full-term infants, which means that the preterm infants have a larger percentage of less restful nighttime sleep. In other studies preterm infants show an over-proportional frequency of attention deficit hyperactivity disorder (ADHD). For this reason, future analyses should reveal whether or not actigraphic monitoring is a suitable means for an early identification of activity-rest behavior in children who may develop ADHD.

Sleeping and waking state development in preterm infants

BACKGROUND

Most studies of sleep-wake states of preterm infants have been cross-sectional. Thus, the extent to which sleep-wake development occurs within individuals and how environmental factors affect the development of sleeping and waking is unclear.

AIMS

This study examined the development of sleeping and waking during the preterm and early post-term periods and the effects of infant health and environmental characteristics.

DESIGN

Longitudinal, descriptive design.

PARTICIPANTS

134 preterm infants at high risk for developmental problems because of birthweights under 1500 g or mechanical ventilation.

OUTCOME MEASURES

Weekly 2-h behavioral observations were conducted from the time infants were no longer critically ill until 43 weeks post-conceptional age or discharge. A single follow-up observation was conducted 1-3 months later.

RESULTS

Active sleep, large body movements and the percent of no REM during active sleep decreased with age, and quiet waking, active waking, quiet sleep and regularity of respiration in active sleep and quiet sleep increased. The state of sleep-wake transition increased until 40 weeks and then decreased after 43 weeks CA. Negative facial expressions showed a quadratic decrease over age. Active waking, active sleep, negative facial expressions and quiet sleep regularity showed a change of development after term. Infant characteristics, illness severity and medical treatments, the handling due to performing an EEG and hospital had only minor effects.

CONCLUSIONS

Significant development of sleeping and waking occurs over the preterm period. Additional research is needed to determine how the change from the hospital to the home environment affects on these developmental trajectories.

Ultradian and circadian activity-rest rhythms of preterm neonates compared to full-term neonates using actigraphic monitoring

During the first weeks of life, preterm neonates show fewer circadian rhythms in their physiological parameters than full-term neonates. To determine whether preterm neonates differ in their temporal adaptation to the day-night cycle from full-term neonates at the early age of 1 week, we compared activity-rest behavior of both groups. Activity-rest behavior of 10 neurologically healthy preterm neonates (born in 34th to 36th week of gestation) and 10 neurologically healthy full-term neonates (born in 37th to 42nd week of gestation) was monitored longitudinally for 8 successive days in the first 2 weeks of life. Actigraphy was used to register and display time patterns of activity and rest in neonates by using small actometers, which resemble a wristwatch. Nursing/feeding was recorded using the actometer's integrated event marker button. Recordings for preterm neonates were conducted in the hospital, recordings for full-term neonates were carried out in the hospital and in their homes. In addition to the actigraphic recordings, a standardized diary was kept regularly. To assess periodic characteristics, frequency components of activity-rest behavior were analyzed using fast Fourier transformation (FFT). Amounts of daily sleep time, nightly sleep time, and sleep time during 24h were compared. Nursing/feeding epochs were also analyzed for 5 preterm and 5 full-term neonates to compare their food intake behavior. The majority of preterm neonates showed a multitude of ultradian frequencies in their spectra. In contrast, several full-term neonates showed a distinct circadian frequency. In preterm neonates, average nightly sleep and average daily sleep of all recorded days were very similar, but after the fourth day of life, only average nightly sleep increased. In full-term neonates, average nightly and daily sleep time of all recorded days differed by about 1h. Average sleep time during 24h for preterm and full-term neonates was similar. Preterm neonates showed longer intervals between events of food intake than full-term neonates. The circadian peaks in the frequency spectra of full-term neonates may indicate the initial adaptation in the first week of life to a 24h day. This is in agreement with our results concerning the different durations of nightly and daily sleep. The increase in nightly sleep time of preterm neonates may be attributed to the progressing adaptation to a circadian activity-rest pattern.

Effect of sleep state on the flash visual evoked potential. A case study

Controversy exists regarding the influence of sleep state on the flash visual evoked potential. This study recorded the visual evoked potential in a new-born infant in four different sleep states; wakefulness. drowsiness, active sleep and quiet sleep over a five hour period. The infant's heart rate, breathing rate and breathing regularity were also recorded. It was clear that when this subject was awake the VEPs recorded differed substantially from those recorded when sleeping. Two of the four main components had shorter peak latencies, one component was prolonged and one of the peak to trough amplitudes was consistently smaller when alert. This study highlights an important and often overlooked aspect of developmental research that the state of the infant may affect developmental measures.

Circadian changes of heart rate in West syndrome

Patterns of circadian and ultradian rhythms in the heart rate (HR) are described in a full-term baby with birth asphyxia and convulsions. A 24h HR recording was carried out at the age of 1, 15, 56, 289, and 295 days; West syndrome diagnosis was made when the patient was 3 months old. The HR showed no circadian rhythm in the follow-up, whereas it is known that the circadian rhythm appears in healthy infants at the age of 1 month and remains thereafter. This observation may be an indirect indicator of the interference of West syndrome with centers of neurological maturity.

Differential effects of breast- and formula-feeding on preterm infants' sleep-wake patterns

OBJECTIVE

To compare sleep-wake patterns of breastfed and formula-fed preterm infants.

DESIGN

Data were taken from an exploratory study of infant biorhythm maturation. Parents completed a 24-hour diary of infant Sleep, Awake, and Cry states and feedings, recorded at 30-minute intervals. Infant health data were collected from medical records and parents' reports.

SETTING

Infants were studied in the home after discharge from a neonatal intensive-care unit.

PARTICIPANTS

The convenience sample included 12 breastfed and 25 formula-fed preterm infants (gestational age, 26-33 weeks; corrected postnatal age, 4-6 weeks). Groups were comparable in terms of gestational age, postnatal age, Apgar scores, maternal age, and home environment.

MAIN OUTCOME MEASURE

The 24-hour recording period was divided into day (0600-1800) and night (1800-0600). Study variables were Day, Night, and 24-hour Sleep, Awake, and Cry.

RESULTS

Breastfed preterm infants exhibited more Day Cry and 24-hour Cry than did formula-fed infants. Infants demonstrated a diurnal pattern in Cry, Awake, and Sleep. Breastfed preterm infants cried approximately 1 hour per day more than formula-fed infants.

CONCLUSION

Preterm breastfed infants experienced more cry than did formula-fed infants. The relationship between feeding method and sleep-wake pattern has implications for supporting lactation as well as for research design.

Ultradian and circadian rhythms of sleep-wake and food-intake behavior during early infancy

The early development of sleep-wake and food-intake rhythms in human infants is reviewed. The development of a 24 h day-night rhythm contains two observable developmental processes: the alterations in the periodic structure of behavior (decreased ultradian, increased circadian components) and the process of synchronization to external time (entrainment). The authors present the results of their studies involving 26 German children and compare them with previous investigations. In their research, it became evident that, during the first weeks of life, the time pattern of sleep-wake and food-intake behavior is characterized by different ultradian periodicities, ranging from 2 h to 8 h. In the course of further ontogenesis, the share of ultradian rhythms in the sleep-wake behavior decreases, while it remains dominant for food-intake behavior. The circadian component is established as early as the first weeks of life and increases in the months that follow. Besides, the authors' study supports the notion of broad interindividual variation in ultradian rhythms and in the development of a day-night rhythm. Examples of free-running rhythms of sleep-wake and food-intake behavior by various authors are strong indicators of the endogenous nature of the circadian rhythms in infants and show that the internal clock is already functioning at birth. It is still uncertain when the process of synchronization to external and social time cues begins and how differences in the maturation of perceptive organs affect the importance of time cues for the entrainment. Prepartally, the physiological maternal entrainment factors and mother-fetus interactions may be most important; during the first weeks of life, the social time cues gain importance, while light acts as a dominant "zeitgeber" at a later time only.

Temporal organization of sleep-wake states in preterm infants

The development of temporal organization of sleep-wake states during the preterm period was examined. Seventy-one high-risk preterms from two cohorts were observed from 7 to 11 p.m. weekly from the time they were no longer critical until discharge. Mixed general linear model analyses found that with increasing postconceptional age, quiet waking, active waking, and sleep-wake transition bouts occurred more frequently, quiet sleep bouts occurred less frequently, and active waking and quiet sleep bouts increased in length. However, these developmental patterns were not stable over cohorts. On the other hand, the transitional probabilities between states were similar in both cohorts, providing evidence for biological bases for some aspects of temporal organization. Active sleep was pivotal in state transitions. Younger infants showed fewer transitions that did not involve active sleep. Thus, temporal organization is an early characteristic of sleep-wake states but is not a unitary phenomenon. Transitional probabilities remain relatively invariant, whereas bouts lengths and frequencies may be altered in different populations or by differing environmental conditions.

Developing circadian rhythmicity. Basic and clinical aspects

Increasing evidence indicates that the circadian timing system is a fundamental hemostatic system that potently influences human behavior and physiology throughout development. Circadian clock function begins during fetal life, and photic regulation of circadian phase is present at birth in primates. After birth, there is progressive maturation of the circadian system, with day-night rhythms in activity and hormone secretion developing between 1 and 3 months of age. Several disorders of the circadian system are now recognized and include clock disorders and problems related to inadequate entrainment of circadian phase. Treatments for several circadian system disorders are now available and include light therapy and melatonin. With the continued elucidation of circadian system development and influences on human physiology and illness, it is anticipated that consideration of circadian biology will become an increasingly important component of clinical care.