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

Associations between Birth Weight and Adult Sleep Characteristics: A Cross-Sectional Analysis from the UAEHFS

Abnormal birth weight, particularly low birth weight (LBW), is known to have long-term adverse health consequences in adulthood, with disrupted sleep being suggested as a mediator or modifier of this link. We thus aimed to assess the associations between birth weight and self-reported adult sleep characteristics: sleep duration, difficulty waking up in the morning, daily nap frequency, sleep problems at night, snoring, daytime tiredness or sleepiness, and ever-stop breathing during sleep. This cross-sectional analysis used the United Arab Emirates Healthy Future Study data collected from February 2016 to March 2023 involving 2124 Emiratis aged 18-61 years. We performed a Poisson regression under unadjusted and age-sex-and-BMI-adjusted models to obtain the risk ratio and its 95% confidence interval for our analysis of the association between birth weight and each adult sleep characteristics, compared to individuals with normal birth weight (≥2.5 kg). Those with LBW had significantly a 17% increased risk of difficulty waking up in the morning, compared to those with normal birth weight. In addition, females with LBW history were also at an increased risk of reporting difficulty waking up in the morning. Studies with objective sleep assessments that include measurements of more confounding factors are recommended to confirm these risks.

Preterm toddlers have low nighttime sleep quality and high daytime activity

A number of studies have been made on the sleep characteristics of children born preterm in an attempt to develop methods to address the sleep problems commonly observed among such children. However, the reported sleep characteristics from these studies vary depending on the observation methods used, i.e., actigraphy, polysomnography and questionnaire. In the current study, to obtain reliable data on the sleep characteristics of preterm-born children, we investigated the difference in sleep properties between 97 preterm and 97 term toddlers of approximately 1.5 years of age using actigraphy. Actigraphy units were attached to the toddlers' waists with an adjustable elastic belt for 7 consecutive days, and a child sleep diary was completed by their parents. In the study, we found that preterm toddlers had more nocturnal awakenings and more daytime activity, suggesting that preterm-born children may have a different process of sleep development in their early development.

The Impact of Preterm Birth on Sleep through Infancy, Childhood and Adolescence and Its Implications

There is emergent literature on the relationship between the development of sleep-wake cycles, sleep architecture, and sleep duration during the neonatal period on neurodevelopmental outcomes among children born preterm. There is also a growing literature on techniques to assess sleep staging in preterm neonates using either EEG methods or heart and respiration rate. Upon discharge from hospital, sleep in children born preterm has been assessed using parent report, actigraphy, and polysomnography. This review describes the ontogeny and measurement of sleep in the neonatal period, the current evidence on the impact of preterm birth on sleep both in the NICU and in childhood and adolescence, and the interaction between sleep, cognition, and social-emotional outcomes in this population.

Early development of sleep and brain functional connectivity in term-born and preterm infants

The proper development of sleep and sleep-wake rhythms during early neonatal life is crucial to lifelong neurological well-being. Recent data suggests that infants who have poor quality sleep demonstrate a risk for impaired neurocognitive outcomes. Sleep ontogenesis is a complex process, whereby alternations between rudimentary brain states-active vs. wake and active sleep vs. quiet sleep-mature during the last trimester of pregnancy. If the infant is born preterm, much of this process occurs in the neonatal intensive care unit, where environmental conditions might interfere with sleep. Functional brain connectivity (FC), which reflects the brain's ability to process and integrate information, may become impaired, with ensuing risks of compromised neurodevelopment. However, the specific mechanisms linking sleep ontogenesis to the emergence of FC are poorly understood and have received little investigation, mainly due to the challenges of studying causal links between developmental phenomena and assessing FC in newborn infants. Recent advancements in infant neuromonitoring and neuroimaging strategies will allow for the design of interventions to improve infant sleep quality and quantity. This review discusses how sleep and FC develop in early life, the dynamic relationship between sleep, preterm birth, and FC, and the challenges associated with understanding these processes. IMPACT: Sleep in early life is essential for proper functional brain development, which is essential for the brain to integrate and process information. This process may be impaired in infants born preterm. The connection between preterm birth, early development of brain functional connectivity, and sleep is poorly understood. This review discusses how sleep and brain functional connectivity develop in early life, how these processes might become impaired, and the challenges associated with understanding these processes. Potential solutions to these challenges are presented to provide direction for future research.

A non-parametric model: free analysis of actigraphic recordings of acute insomnia patients

Both parametric and non-parametric approaches to time-series analysis have advantages and drawbacks. Parametric methods, although powerful and widely used, can yield inconsistent results due to the oversimplification of the observed phenomena. They require the setting of arbitrary constants for their creation and refinement, and, although these constants relate to assumptions about the observed systems, it can lead to erroneous results when treating a very complex problem with a sizable list of unknowns. Their non-parametric counterparts, instead, are more widely applicable but present a higher detrimental sensitivity to noise and low density in the data. For the case of approximately periodic phenomena, such as human actigraphic time series, parametric methods are widely used and concepts such as acrophase are key in chronobiology, especially when studying healthy and diseased human populations. In this work, we present a non-parametric method of analysis of actigraphic time series from insomniac patients and healthy age-matched controls. The method is fully data-driven, reproduces previous results in the context of activity offset delay and, crucially, extends the concept of acrophase not only to circadian but also for ultradian spectral components.

Disturbed sleep in children born extremely preterm is associated with behavioural and emotional symptoms

AIM

To determine whether children born extremely preterm are at increased risk for sleep disturbances and to explore relationships between extremely preterm birth, sleep and attention-deficit/hyperactivity disorder (ADHD) symptoms and emotional symptoms.

METHOD

EPICure2 cohort study. Parents of 165 children born ≤26 weeks' gestation (53% male) and 121 children born at term (43% male) completed the Children's Sleep Habits Questionnaire, sleep disordered breathing subscale of the Pediatric Sleep Questionnaire, the emotional problems scale of the Strengths and Difficulties Questionnaire and the ADHD Rating Scale-5 at 11 years of age.

RESULTS

Extremely preterm children had greater habitual snoring (adjusted odds ratio 6.8; 95% confidence interval 2.3, 20.3), less frequently fell asleep within 20 minutes (Cohen's d 0.33), higher night wakings (d 0.44) and daytime sleepiness scores (d 0.40) than term-born children; there was no between-group difference in sleep duration scores. Among children without severe disability, night wakings scores partially mediated the relationship between preterm birth and inattention (additional 5% of variance explained), hyperactivity/impulsivity (13%) and emotional problems (9%). Snoring partially mediated the relationship between preterm birth, hyperactivity/impulsivity and inattention (additional 1-5% of variance).

CONCLUSION

Children born extremely preterm are at increased risk of disturbed sleep compared to term-born children. As night wakings partially mediated the relationship between preterm birth and ADHD symptoms and emotional problems, reducing sleep disturbance may improve sleep and reduce attention and emotional problems in this population.

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.

Characterizing Behavioral Activity Rhythms in Older Adults Using Actigraphy

Wrist actigraphy has been used to assess sleep in older adult populations for nearly half a century. Over the years, the continuous raw activity data derived from actigraphy has been used for the characterization of factors beyond sleep/wake such as physical activity patterns and circadian rhythms. Behavioral activity rhythms (BAR) are useful to describe individual daily behavioral patterns beyond sleep and wake, which represent important and meaningful clinical outcomes. This paper reviews common rhythmometric approaches and summarizes the available data from the use of these different approaches in older adult populations. We further consider a new approach developed in our laboratory designed to provide graphical characterization of BAR for the observed behavioral phenomenon of activity patterns across time. We illustrate the application of this new approach using actigraphy data collected from a well-characterized sample of older adults (age 60+) with osteoarthritis (OA) pain and insomnia. Generalized additive models (GAM) were implemented to fit smoothed nonlinear curves to log-transformed aggregated actigraphy-derived activity measurements. This approach demonstrated an overall strong model fit (R2 = 0.82, SD = 0.09) and was able to provide meaningful outcome measures allowing for graphical and parameterized characterization of the observed activity patterns within this sample.

Sleep Duration and Nocturnal Awakenings in Infants Born with Gestational Risk

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSION

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

Waking up too early - the consequences of preterm birth on sleep development

Good quality sleep of sufficient duration is vital for optimal physiological function and our health. Sleep deprivation is associated with impaired neurocognitive function and emotional control, and increases the risk for cardiometabolic diseases, obesity and cancer. Sleep develops during fetal life with the emergence of a recognisable pattern of sleep states in the preterm fetus associated with the development, maturation and connectivity within neural networks in the brain. Despite the physiological importance of sleep, surprisingly little is known about how sleep develops in individuals born preterm. Globally, an estimated 15 million babies are born preterm (<37 weeks gestation) each year, and these babies are at significant risk of neural injury and impaired brain development. This review discusses how sleep develops during fetal and neonatal life, how preterm birth impacts on sleep development to adulthood, and the factors which may contribute to impaired brain and sleep development, leading to altered neurocognitive, behavioural and motor capabilities in the infant and child. Going forward, the challenge is to identify specific risk factors for impaired sleep development in preterm babies to allow for the design of interventions that will improve the quality and quantity of sleep throughout life.

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

STUDY OBJECTIVES

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Occupational Health and Sleep Issues in Underserved Populations

Sleep disorders and occupational hazards, injuries, and illnesses impact an individual's overall health. In the United States, substantial racial, ethnic, and socioeconomic disparities exist in sleep and occupational health. Primary care physicians working in underserved communities should be aware of this disparity and target these higher-risk populations for focused evaluation and intervention.

Circadian Sleep Patterns in Toddlers Born Preterm: Longitudinal Associations with Developmental and Health Concerns

OBJECTIVE

Children born preterm are at elevated risk for several developmental and health concerns. Early sleep patterns may be associated with these concerns. The current study assesses the associations between toddler circadian sleep/activity patterns and later developmental, behavioral, attentional, and health concerns in this at-risk population.

METHOD

We examined circadian sleep/activity patterns at 2 years of age in 99 children born preterm. Child cognitive skills were tested at 3 years of age, and behavior, attention, and health concerns were reported at 3 and 6 years of age. First, sleep/activity data collected via actigraphy were assessed using time series analysis (TSA). For this, we assessed how each child's sleep/activity pattern compared to a specified 24-hour circadian cycle (SCC) with an adjustment for daytime napping. Second, in a series of regression models child sleep/activity parameters from the TSA were assessed with child gender, prematurity, and family sociodemographic assets as covariates.

RESULTS

Toddlers with patterns that closely aligned with the SCC had higher abbreviated intelligence quotient scores at 3 years of age. Additionally, at 6 years these children had a lower risk for illness-related medical visits. Higher toddler average activity level was associated with fewer teacher-reported attention-deficit hyperactivity disorder symptoms and a lower risk for illness-related medical visits.

CONCLUSION

The novel approach used in this study to index child circadian patterns provides a pattern-based analysis of sleep/activity, which may prove to be developmentally consequential. With replication, these findings may help practitioners promote optimal cognitive and health development via circadian sleep supports in infants born preterm.

Advanced sleep phase in adolescents born preterm

The objective of this article is to evaluate whether sleep patterns and quality differed between adolescents born preterm and term, and to further explore whether differences in sleep patterns were explained by differences in mediating factors such as mood, behavior, or socioeconomic status. Five hundred and one 16- to 19-year-old children in the longitudinal Cleveland Children's Sleep and Health Study cohort underwent overnight polysomnography (PSG), wore wrist actigraphs, and completed sleep logs for 1 week. The modified Epworth Sleepiness Scale, the Adolescent Sleep Hygiene Scale, and the Adolescent Sleep-Wake Scale were used to further assess sleep. Adolescents born preterm demonstrated significantly (p < .05) earlier bed and wake times and sleep midpoints (approximately 22 min after adjusting for demographic and psychosocial factors) by actigraphy. They also had significantly fewer arousals (by PSG), and reported being more rested and alert in the morning, as well as less sleepiness and fatigue. These findings support a growing body of evidence that perinatal factors may influence sleep phenotypes later in life. These factors may reflect developmental influences, as well as the influence of parenting styles on children's sleep.

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.

Advanced sleep-wake rhythm in adults born prematurely: confirmation by actigraphy-based assessment in the Helsinki Study of Very Low Birth Weight Adults

OBJECTIVE

Previous studies have suggested a propensity towards morningness in teenagers and adults born preterm. We set out to study sleep in a subsample from The Helsinki Study of Very Low Birth Weight Adults cohort, with emphasis on sleep timing, duration, and quality. We compared young adults who were born prematurely at very low birth weight (VLBW; <1500 g) with controls born at term.

METHODS

We measured sleep by actigraphy in young adults aged 21-29 years. A total of 75 individuals (40 VLBW and 35 controls) provided adequate data. Group differences in sleep parameters were analyzed using t-test and linear regression models.

RESULTS

VLBW adults woke up on average 40 min earlier [95% confidence interval (CI), 9-70] and reported 40 min earlier get up time (95% CI, 8-71) than did the controls. The difference remained after adjustment for confounders. We found no group difference in sleep duration or measures of sleep quality.

CONCLUSION

Our findings of earlier rising in the VLBW group are suggestive of an advanced sleep phase in that group. These results reinforce previous suggestions that chronotype may be programmed early during life.

Relation between sleep status of preterm infants aged 1-2 years and mothers' parenting stress

BACKGROUND

The aim of this study was to compare infants' sleep measures through an actigraph and maternal parenting stress among preterm and full-term mothers, and to explore the factors affecting maternal parenting stress in relation to infants' sleep.

METHODS

The subjects were 44 pairs of mothers and children. Twenty-one were in the preterm group, and 23 were in the full-term group. Inclusion criteria for preterm infants were born at less than 36 weeks and birthweight of less than 2500 g. The Parenting Stress Index (PSI) Short Form assesses maternal perception of the degree of parenting stress: the children's domain, and the parent's domain. An actigraph was applied to assess the infants' sleep measures.

RESULTS

The PSI showed significant differences, with high scores in parenting stress in the preterm group. Also, the number of mothers who complained about their infant's sleep issues was significantly higher in the preterm group. Most of the sleep measures showed improvement by their age in both preterm and full-term infants. Multiple linear regression analysis showed that sleep efficiency, longest sleep duration at nighttime accounted for 71% of stress in the children's domain of the PSI of the preterm group.

CONCLUSION

The parenting stress among mothers of preterm infants was significantly higher than that of mothers of full-term infants. The mothers of preterm infants were concerned about their infant's nocturnal sleep quality.

Very low birth weight infants after discharge: What do parents describe?

BACKGROUND

Morbidity and mortality in Very Low Birth Weight (VLBW) infants during their hospital stay have been well described. However, there are insufficient data regarding health problems after discharge.

STUDY DESIGN

In a multicenter study performed between January 2009 and December 2010 including 2493 VLBW infants, questionnaires were sent out to all participating parents in the first year of life. We compared the parental reported health of VLBW infants with a national cohort (KIGGS).

RESULTS

The reported health of VLBW infants born after 29 weeks of gestation was identical to term infants. Even in the group of infants born before 24 weeks of gestation health was regarded as very good or good in >70% of cases. However, parents described a delayed development in >50% increasing to >70% with lower gestational age. In the first year of life VLBW infants have an increased risk of visual and hearing problems. Bronchitis was more frequent in VLBW infants but there were no differences in other infections typical for that age group. VLBW infants had less sleeping problems. No gender differences were described.

CONCLUSION

VLBW infants in our study require slightly more medical care compared to their peers. However, medical problems are relatively small compared to the developmental needs as perceived by their parents. Therefore, close follow-up and advice by specialists in infant development are needed.

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.

Activity-based assessment of the sleep behaviors of VLBW preterm infants and full-term infants at around 12 months of age

PURPOSE

The aim of this study is to identify the characteristics of sleep behaviors assessed from activity data among very low-birth weight (VLBW) preterm infants in comparison to full-term infants at the age of around 12 corrected months, due to the possibility that sleep behaviors of preterm infants may be different from those of full-term infants.

METHOD

Cross-sectional study. Infant sleep measures were obtained through actigraphs (Micro-mini RC, Ambulatory Monitoring Inc., Ardsley, NY), which were attached to the infants' ankles during a week-long period. The subjects were 14 preterm infants and 14 full-term infants in which the mean ages were 13.3+/-2.1 corrected months and 12.3+/-2.4 month, respectively.

RESULTS

Preterm infants showed significantly less sleep duration during nighttime than full-term infants. The mean activity score and ACTX (Activity Index: percentage minutes with more than 0 activity score) of preterm infants during nighttime were significantly higher than those of full-term infants. No significant differences in total sleep duration, daytime sleep duration, the number of night-wakings, and sleep efficiency were found between the two groups.

CONCLUSION

Preterm infants slept less and had a larger percentage of less restful sleep during nighttime. The results indicated that prematurity at the time of birth remained throughout the developmental course of sleep behaviors among preterm infants at around the age of 12 corrected months.

Size at birth and motor activity during stress in children aged 7 to 9 years

OBJECTIVES

Small size at birth is linked with metabolic and cardiovascular disease. There is increasing evidence that it is also linked with physiologic stress responses and abnormal behavior, in particular, symptoms of hyperactivity. Therefore, we investigated associations between size at birth and motor activity during psychosocial stress.

METHODS

In 123 children aged 7 to 9 years, we examined the relations of birth weight, head circumference, length, and ponderal index at birth with motor activity on exposure to both stress and nonstress situations. Videos were recorded while the children performed a story and a math task in front of an audience (stress) and watched a movie (nonstress); motor activity was defined as lifting or tilting of a foot.

RESULTS

Children who had had a smaller head circumference at birth demonstrated greater motor activity during the stress test. There were marked gender differences in the results. In boys, lower birth weight, head circumference, and ponderal index were associated with greater motor activity during the stress test but not associated with motor activity during the nonstress situation. The findings remained significant when potential confounding variables were controlled for. There were no associations in girls.

CONCLUSIONS

The findings suggest long-term effects of an adverse fetal environment on the behavioral stress response in boys and parallel similar gender-specific effects on different stress response systems in humans and animals. The results could reflect permanent alterations of dopaminergic neurotransmission and have implications for the etiology of clinical hyperactivity.