Low birth weight and neurocognitive status at six years of age

Predicting long-term neurocognitive outcome after pediatric intensive care unit admission for bronchiolitis-preliminary exploration of the potential of machine learning

PURPOSE

For successful prevention and intervention, it is important to unravel the complex constellation of factors that affect neurocognitive functioning after pediatric intensive care unit (PICU) admission. This study aims (1) to elucidate the potential relevance of patient and PICU-related characteristics for long-term adverse neurocognitive outcome after PICU admission for bronchiolitis, and (2) to perform a preliminary exploration of the potential of machine learning as compared to linear regression to improve neurocognitive outcome prediction in a relatively small sample of children after PICU admission.

METHODS

This cross-sectional observational study investigated 65 children aged 6-12 years with previous PICU admission for bronchiolitis (age ≤ 1 year). They were compared to demographically comparable healthy peers (n = 76) on neurocognitive functioning. Patient and PICU-related characteristics used for the prediction models were as follows: demographic characteristics, perinatal and disease parameters, laboratory results, and intervention characteristics, including hourly validated mechanical ventilation parameters. Neurocognitive outcome was measured by intelligence and computerized neurocognitive testing. Prediction models were developed for each of the neurocognitive outcomes using Regression Trees, k-Nearest Neighbors, and conventional linear regression analysis.

RESULTS

The patient group had lower intelligence than the control group (p < .001, d = -0.59) and poorer performance in neurocognitive functions, i.e., speed and attention (p = .03, d = -0.41) and verbal memory (p < .001, d = -0.60). Lower intelligence was predicted by lower birth weight and lower socioeconomic status (R2 = 25.9%). Poorer performance on the speed and attention domain was predicted by younger age at follow-up (R2 = 53.5%). Poorer verbal memory was predicted by lower birth weight, younger age at follow-up, and greater exposure to acidotic events (R2 = 50.6%). The machine learning models did not reveal added value in terms of model performance as compared to linear regression.

CONCLUSION

The findings of this study suggest that in children with previous PICU admission for bronchiolitis, (1) lower birth weight, younger age at follow-up, and lower socioeconomic status are associated with poorer neurocognitive outcome; and (2) greater exposure to acidotic events during PICU admission is associated with poorer verbal memory outcome. The findings of this study provide no evidence for the added value of machine learning models as compared to linear regression analysis in the prediction of long-term neurocognitive outcome in a relatively small sample of children.

WHAT IS KNOWN

• Adverse neurocognitive outcomes are described in PICU survivors, which are known to interfere with development in other major domains of functioning, such as mental health, academic achievement, and socioeconomic success, highlighting neurocognition as an important outcome after PICU admission. • Machine learning is a rapidly growing field of artificial intelligence that is increasingly applied in health care settings, with great potential to capture the complexity of outcome prediction.

WHAT IS NEW

• This study shows that lower birth weight, lower socioeconomic status, and greater exposure to acidotic events during PICU admission for bronchiolitis are associated with poorer long-term neurocognitive outcome after PICU admission. Results provide no evidence for the added value of machine learning models in a relatively small sample of children. • As bronchiolitis seldom manifests neurologically, the relation between acidotic events and neurocognitive outcome may reflect either potentially harmful effects of acidosis itself or related processes such as hypercapnia or hypoxic and/or ischemic events during PICU admission. This study further highlights the importance of structured follow-up to monitor long-term outcome of children after PICU admission.

Heterogeneity of the attentional system's efficiency among very prematurely born pre-schoolers

Very preterm birth increases the risk of ADHD as well as other neurodevelopmental disorders. Deficits within the attentional system were previously signaled in preterm children; however, studies lacked in consideration of an intragroup differentiation. Thus, this study aimed to verify whether deficits in the attentional mechanisms are inter-individually differentiated among very prematurely born children and if so, which biomedical and non-biomedical factors are associated with the profile of deficits within the attentional system. We tested the efficiency of attentional processes among 5-year-old children with the Attention Network Task - Child Version. The results have indicated that 26% of very preterm children presented with the suboptimal functioning of the attentional system (more than 1 SD below mean score of full-term children in attentional alerting and orienting), whereas 74% were characterized by the normal efficiency of attention. The profile of attentional deficits observed among very preterm preschoolers was associated with significantly lower birth weight and decreased family living standard. Very prematurely born children are thus a relatively heterogeneous group in terms of the efficiency of attentional system and deficits apply to only some of those children. Early developmental support aimed at enhancing attentional functioning should be addressed to children with lower birth weight in the first place.

Reading and spelling skills of prematurely born children in light of the underlying cognitive factors

Prematurity is a serious risk factor for learning difficulties. Within the academic skills reading has the greatest impact on the prospects of the students; therefore, studying the reading skills in the risk populations is very important. The aim of our study was to investigate reading and spelling skills of prematurely born children. Our target group consisted of 8-11-year-old children (n = 23) who were born preterm with very low birthweights (VLBW). For comparison 57 full-term children (27 good readers and 30 dyslexics) were included in the study sample. To assess the reading and spelling abilities the Hungarian version of the 3DM (Dyslexia Differential Diagnosis) was used. Cognitive abilities were tested using the Hungarian adaptation of the WISC-IV and the Rey Complex Figure Test. The data were analyzed with a novel statistical approach using the R program. In the cognitive measures the mean performances of all three groups fell within the normal range. In the WISC-IV Full-scale IQ as well as in some other cognitive measures the good readers significantly outperformed both the dyslexics and the preterms. The findings of the study did not confirm our expectation that VLBW prematurity should lead to developmental disadvantages in the acquisition of reading and spelling skills since in the reading and spelling performances of the good readers and the preterms did not differ, while both the good readers and the preterms scored higher than the dyslexics. The results suggest that the cognitive assets of the preterm children contributing to their reading and spelling performances were their good spatial-visual memory, working memory, and processing speed. The identification of the cognitive mechanisms underlying reading and spelling abilities is of crucial importance for designing intervention for children with deficits in these academic skills.

Spatial Thinking in Term and Preterm-Born Preschoolers: Relations to Parent-Child Speech and Gesture

Spatial skills predict important life outcomes, such as mathematical achievement or entrance into Science, Technology, Engineering, and Mathematics (STEM) disciplines. Children significantly vary in their spatial performance even before they enter formal schooling. One correlate of children's spatial performance is the spatial language they produce and hear from others, such as their parents. Because the emphasis has been on spatial language, less is known about the role of hand gestures in children's spatial development. Some children are more likely to fall behind in their spatial skills than others. Children born premature (gestational age <37 weeks) constitute such a risk group. Here, we compared performance of term and preterm-born children on two non-verbal spatial tasks-mental transformation and block design. We also examined relations of children's performance on these tasks to parental spatial language and gesture input and their own production of spatial language and gesture during an independent puzzle play interaction. We found that while term and preterm-born children (n = 40) as a group did not differ in the mental transformation or block design performance, children varied widely in their performance within each group. The variability in mental transformation scores was predicted by both a subset of spatial words (what aspects of spatial information) and all spatial gestures children produced. Children's spatial language and gesture were in turn related to their parents' spatial language and gesture. Parental spatial language and gesture had an indirect relation on children's mental transformation, but not block design, scores via children's spatial language, and gesture use. Overall, results highlight the unique contributions of speech and gesture in communicating spatial information and predicting children's spatial performance.

Financial strain and birth weight: the mediating role of psychological distress

The effects of financial strain during pregnancy have received limited attention. In addition, data examining the pathways by which SES indicators contribute to birth weight are lacking. The objective of the current study was to examine the potential pathway of psychological distress in the relationship between financial strain and birth weight. Participants consisted of 138 pregnant women who completed measures assessing financial strain, depressive symptoms, pregnancy-specific distress, perceived stress, and general anxiety during pregnancy (mean gestational age = 18.5, SD = 7.2). Birth outcome data were obtained via medical record review. Simple and parallel mediation models were conducted using PROCESS. Simple mediation models showed that depressive symptoms (95% CI -24.65, -0.90) and pregnancy-specific distress (95% CI -37.31, -5.91), but not perceived stress (95% CI -31.17, 4.69) or anxiety (95% CI -25.84, 5.57), served as mediators in the relationship between financial strain and birth weight. When depressive symptoms and pregnancy-specific distress were included in the same mediation model, only pregnancy-specific distress remained significant. Financial strain was positively associated with all facets of psychological distress and negatively associated with birth weight during pregnancy. The current study demonstrated the mechanistic role of pregnancy-specific distress in the link between financial strain and birth weight in a racially diverse sample. Interventions targeting pregnancy-specific distress may mitigate the effects of financial strain on birth weight. Studies examining whether pregnancy-specific distress accounts for the relationship between other types of stressor exposures and birth weight would be informative.

Multifactorial determinants of cognition - Thyroid function is not the only one

Background

Since the 1960s hypothyroidism together with iodine deficiency have been considered to be a principal determinant of cognition development. Following iodine supplementation programs and improved treatment options for hypothyroidism this relation might not be valid in 2015. On the other hand neurosciences have added different inputs also related to cognition.

Scope of review

We will examine the characteristics of the original and current publications on thyroid function and cognition and also add some general determinants of intelligence and cognition. One central issue for us is the relation of stress to cognition knowing that both physical and psychological stress, are frequent elements in subjects with thyroid dysfunction. We have considered a special type of stress called pre-natal stress which can influence cognitive functions. Fear and anxiety can be intermingled requiring mechanisms of fear extinction.

Major conclusions

Recent studies have failed to show an influence of thyroid medication during pregnancy on intellectual development. Neuroscience offers a better explanation of cognition than hypothyroidism and iodine deficiency. Additional factors relevant to cognition are nutrition, infection, prenatal stress, and early life stress. In turn stress is related to low magnesium levels. Magnesium supplementation can correct both latent hypothyroidism and acquired mild cognitive deficits.

General significance

Cognition is a complex process that depends on many determinants and not only on thyroid function. Magnesium deficiency appears to be a basic mechanism for changes in thyroid function as well as of cognition.

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Untreated hypothyroidism, i.e. hypothyroxinemia, can influence IQ.

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Thyroxine administration to euthyroid pregnant women has no effect on cognition.

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The hippocampus and NMDA receptors play a central role in cognitive processes.

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Antenatal and early life stressors can influence cognition later in life.

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Stressors can lead to decreased levels of magnesium and demands supplementation.

Normal birth weight variation and children's neuropsychological functioning: links between language, executive functioning, and theory of mind

The effect of low birth weight on children's development has been documented for a range of neurocognitive outcomes. However, few previous studies have examined the effect of birth weight variability within the normal range on children's neuropsychological development. The current study examined birth weight variation amongst children weighing ≥2500 g in relation to their language, executive functioning (EF), and theory of mind (ToM), and specified a developmental pathway in which birth weight was hypothesized to be associated with children's EF and ToM through their intermediary language skills. The current study used a prospective community birth cohort of 468 children. Families were recruited when children were newborns and followed up every 18 months until children were age 4.5. Language was assessed at age 3 using a standardized measure of receptive vocabulary (PPVT), and EF and ToM were measured at age 4.5 using previously validated and developmentally appropriate tasks. After controlling for potential confounding variables (family income, parent education, gestational age), birth weight within the normal range was associated with language ability at age 3 (β=.17; p=.012); and the effect of birth weight on both EF (z=2.09; p=.03) and ToM (z=2.07; p=.03) at age 4.5 operated indirectly through their language ability at age 3. Our findings indicate that the effects of birth weight on child neurocognition extend into the normal range of birth weight, and specific developmental mechanisms may link these skills over time.

Biological indicators of the in-utero environment and their association with birth weight for gestational age

Birth weight for gestational age (BW/GA) has been associated with a risk of adverse health outcomes. Biological indices of pregnancy complications, maternal mid-pregnancy serum biomarkers and placental pathology may shed light on these associations, but at present, they are most often examined as single entities and offer little insight about overlap. In addition, these indices are typically assessed in relation to the extremes of the BW/GA distribution, leaving open the question of how they relate to the entire BW/GA distribution. Addressing issues such as these may help elucidate why postnatal health outcomes vary across the BW/GA continuum. In this study, we focused on a subset of women who participated in the Pregnancy Outcomes and Community Health Study (n = 1371). We examined BW/GA (i.e. gestational age and sex-referenced z-scores) in relation to obstetric complications, second trimester maternal serum screening results and histologic evidence of placental pathology along with maternal demographics, anthropometrics and substance use. In adjusted models, mean reductions in BW/GA z-scores were associated with preeclampsia (β = -0.70, 95% CI -1.04, -0.36), high maternal serum alpha fetoprotein (β = -0.28, 95% CI -0.43, -0.13), unconjugated estriol (β = -0.31/0.5 multiples of the median decrease, 95% CI -0.41, -0.21) and high levels of maternal obstructive vascular pathology in the placenta (β = -0.46, 95% CI -0.67, -0.25). The findings were similar when preterm infants, small-for-gestational age or large-for-gestational age infants were excluded. More research is needed to examine how the factors studied here might directly mediate or mark risk when evaluating the associations between BW/GA and postnatal health outcomes.

Associations between birth weight, preeclampsia and cognitive functions in middle-aged adults

Both reductions in birth weight and preeclampsia (PE) have been associated with decrements in scores on tests of intelligence in children and adolescents. We examined whether these decrements persist into middle adulthood and expand into other domains of cognitive functioning. Using data from the Early Determinants of Adult Health project and from the ancillary project, Fetal Antecedents of Major Depression and Cardiovascular Disease, we selected term same-sex sibling sets or singletons from these sets, from the New England Family Study (NEFS) and the Child Health and Development Studies (CHDS), discordant on either fetal growth or PE, to test the hypotheses that prenatal exposure to inflammation was associated with decrements in attention, learning and executive function 40 years later. Exposure was defined as a continuous measure of percentile birth weight for gestational age, reduced fetal growth (<20th percentile of birth weight for gestational age) or maternal PE. Given that the sample was comprised, in part, of sibling sets, the analyses were performed using mixed models to account for the inter-sibling correlations. Analyses were performed separately by study site (i.e. NEFS and CHDS). We found few statistically significant associations (suggesting a possible type II error) consistent with previous literature, suggesting that the associations with low birth weight do not persist into midlife. We discuss the possible reasons for the lack of associations, which include the possible mediating effects of the postnatal environment.

Neurodevelopmental outcomes of infants born prematurely

Long-term follow-up of infants born prematurely is necessary to determine neurodevelopmental outcomes, particularly with the expansion of interest from major disabilities to high prevalence/low severity dysfunctions. Models of pathogenesis include changes due to developmental disruptions and to injury, the magnitude and type of change influenced by the infant's age, and central nervous system recovery and reorganization. Alterations in neurogenesis, migration, myelination, cell death, and synaptogenesis occur even in the absence of insult. Despite increased knowledge regarding these processes, the functional significance of brain abnormalities is unclear. Because of methodologic problems in follow-up studies, it is difficult to characterize outcome definitively. Nonetheless, an acceptable degree of agreement across studies is found with regard to specific neurodevelopmental outcomes: motor/neurologic function, visuomotor integrative skills, IQ, academic achievement, language, executive function, and attention-deficit hyperactivity disorder/behavioral issues. In general, children born prematurely have more problems in these areas than do their normal birth weight counterparts. Suggestions for improved analyses and clarification of outcomes include use of cluster analysis, structural equation modeling, growth curve analysis, developmental epidemiologic approaches, and better control of background variables using risk indexes and factor scores. Better assessment techniques measuring functions documented to be at higher risk of problems are discussed.

Associations between birth weight and attention-deficit/hyperactivity disorder symptom severity: indirect effects via primary neuropsychological functions

BACKGROUND

Attention-deficit/hyperactivity disorder (ADHD) has a range of aetiological origins which are associated with a number of disruptions in neuropsychological functioning. This study aimed to examine how low birth weight, a proxy measure for a range of environmental complications during gestation, predicted ADHD symptom severity in preschool-aged children indirectly via neuropsychological functioning.

METHODS

A total of 197 preschool-aged children were recruited as part of a larger longitudinal study. Two neuropsychological factors were derived from NEPSY domain scores. One, referred to as ‘Primary Neuropsychological Function,’ was loaded highly with Sensorimotor and Visuospatial scores. The other, termed ‘Higher-Order Function’ was loaded highly with Language and Memory domain scores. Executive functioning split evenly across the two. Analyses examined whether these neuropsychological factors allowed for an indirect association between birth weight and ADHD symptom severity.

RESULTS

As both factors were associated with symptom severity, only the Primary Neuropsychological Factor was associated with birth weight. Furthermore, birth weight was indirectly associated to symptom severity via this factor.

CONCLUSIONS

These data indicate that birth weight is indirectly associated with ADHD severity via disruption of neuropsychological functions that are more primary in function as opposed to functions that play a higher-order role in utilising and integrating the primary functions.

Attention difficulties in a contemporary geographic cohort of adolescents born extremely preterm/extremely low birth weight

The aim of this study was to evaluate attention difficulties in a contemporary geographic cohort of adolescents born extremely preterm (EP, <28 weeks' gestation) or extremely low birth weight (ELBW, birth weight <1000 g). The EP/ELBW group included 228 adolescents (mean age = 17.0 years) born in Victoria, Australia in 1991 and 1992. The control group were 166 adolescents (mean age = 17.4 years) born of normal birth weight (birth weight >2499 g) who were recruited in the newborn period and matched to the EP/ELBW group on date of birth, gender, language spoken and health insurance status. Participants were assessed on measures of selective, sustained, and executive (shift and divided) attention, and parents and participants completed behavioral reports. The EP/ELBW group performed more poorly across tests of selective and executive attention, had greater rates of clinically significant difficulties compared with the control group, and also had greater behavioral attention problems as reported by parents. Neonatal risk factors were weakly associated with attention outcomes. In conclusion, higher rates of attention impairments are observed in individuals born EP/ELBW well into adolescence and may have consequences for their transition to adulthood.

A history of low birth weight alters recovery following a future head injury: a case series

OBJECTIVE

Low birth weight (LBW; below 2500 grams) is a general risk factor for a variety of neurodevelopmental difficulties. However, these children may remain more vulnerable to neurologic and environmental insults occurring years later. This prospective case series reports on children who sustained a mild, moderate, or severe traumatic brain injury (TBI) in middle childhood but who had also been born with birth weights below 2500 grams.

PARTICIPANTS

PARTICIPANTS were 14 children with mild, moderate, or severe traumatic brain injury (TBI), 5 of whom had birth weights under 2500 grams (LBW) and 9 children with normal birth weight (NBW). All participants were drawn from a larger study on the long-term cognitive and behavioral impact of pediatric TBI and were matched on age, estimated socioeconomic status (SES), and severity of TBI (with NBW children actually having a slightly worse overall injury severity).

RESULTS

At baseline, both groups exhibited similar scores on WJ-R Letter Word Identification and Calculations, Tower of London number solved, and CVLT-C total correct. Baseline group differences were observed on the CELF-III Formulated Sentences (NBW > LBW) and on the VABS Adaptive Behavior Composite and Socialization subdomain (LBW > NBW). Over 2 years, relative to the NBW group, the LBW group evidenced declines on both WJ-R subtests, CVLT-C total correct, CELF-III Formulated Sentences, and VABS Adaptive Behavior Composite and Socialization.

CONCLUSIONS

Although preliminary in nature due to small sample size, findings suggest a history of LBW influences the recovery trajectory following childhood TBI. Academic and adaptive functioning and verbal memory appeared particularly affected.

Influence of prenatal maternal stress, maternal plasma cortisol and cortisol in the amniotic fluid on birth outcomes and child temperament at 3 months

This prospective, longitudinal study aimed to investigate relationships between indicators of maternal prenatal stress, infant birth outcomes and early temperament. We examined the pattern of associations and postulated pathways between physiological (cortisol plasma concentrations) and self-report indices (stress, anxiety) of maternal prenatal stress, cortisol in the amniotic fluid, birth outcomes and infant temperament at 3 months. The sample consisted of 158 women undergoing amniocentesis in the 2nd trimester of pregnancy. Questionnaire measures of maternal stress and anxiety were found to be unrelated to cortisol in plasma or amniotic fluid. Maternal cortisol was related to amniotic cortisol, which in turn was associated with lower birth weight. Birth weight predicted infant fear and distress to limitation at 3 months old. We found trend-like indirect effects of amniotic fluid on infant distress to limitation and fear via birth weight. This is one of the few studies to simultaneously assess the role of maternal and amniotic fluid cortisol on birth outcomes and infant emotional development. The results suggest that foetal cortisol may be an important predictor of infant outcomes and shed light on the mechanisms through which prenatal maternal stress affects infant psychological health.

Pre- and postnatal drivers of childhood intelligence: evidence from Singapore

This study seeks to investigate what influences intelligence in early childhood. The Singapore Cohort Study of the Risk Factors of Myopia (SCORM) is used to assess determinants of childhood IQ and changes in IQ. This longitudinal data set, collected in 1999, includes a wealth of demographic, socioeconomic and prenatal characteristics. The richness of the data allows various econometric approaches to be employed, including the use of ordered and multinomial logit analysis. Mother's education is found to be a consistent and key determinant of childhood IQ. Father's education and school quality are found to be key drivers for increasing IQ levels above the average sample movement.

Perinatal and socioeconomic risk factors for variable and persistent cognitive delay at 24 and 48 months of age in a national sample

The objective of this paper is to examine patterns of cognitive delay at 24 and 48 months and quantify the effects of perinatal and sociodemographic risk factors on persistent and variable cognitive delay. Using data from 7,200 children in the Early Childhood Longitudinal Study, Birth Cohort (ECLS-B), multiple logistic regression models identified significant predictors of low cognitive functioning at 24 and 48 months. Additional multiple logistic models predicting cognitive delay at 48 months were estimated separately for children with and without delay at 24 months. Of the nearly 1,000 children delayed at 24 months, 24.2% remained delayed by 48 months; 7.9% of the children not delayed at 24 months exhibited delay at 48 months. Low and very low birthweight increased cognitive delay risk at 24, but not 48 months. Low maternal education had a strongly increasing effect (OR = 2.3 at 24 months, OR = 13.7 at 48 months), as did low family income (OR = 1.4 at 24 months, OR = 7.0 at 48 months). Among children delayed at 24 months, low maternal education predicted delay even more strongly at 48 months (OR = 30.5). Low cognitive functioning is highly dynamic from 24 to 48 months. Although gestational factors including low birthweight increase children’s risk of cognitive delay at 24 months, low maternal education and family income are more prevalent in the pediatric population and are much stronger predictors of both persistent and emerging delay between ages 24 and 48 months.

Basic Information Processing Abilities at 11 years Account for Deficits in IQ Associated with Preterm Birth

Although it is well established that preterms as a group do poorly relative to their full-term peers on tests of global cognitive functioning, the basis for this relative deficiency is less understood. The present paper examines preterm deficits in core cognitive abilities and determines their role in mediating preterm/full-term differences in IQ. The performance of 11-year-old children born preterm (birth weight <1750g) and their full-term controls were compared on a large battery of 15 tasks, covering four basic cognitive domains -- memory, attention, speed of processing and representational competence. The validity of these four domains was established using latent variables and confirmatory factor analysis (CFA). Preterms showed pervasive deficits within and across domains. Additionally, preterm deficits in IQ were completely mediated by these four cognitive domains in a structural equation model involving a cascade from elementary abilities (attention and speed), to more complex abilities (memory and representational competence), to IQ. The similarity of findings to those obtained with this cohort in infancy and toddlerhood suggest that preterm deficits persist - across time, across task, and from the non-verbal to the verbal period.

Attention problems in a representative sample of extremely preterm/extremely low birth weight children

The aim of this study was to examine attention in a large, representative, contemporary cohort of children born extremely preterm (EP) and/or extremely low birth weight (ELBW). Participants included 189 of 201 surviving children born EP (<28 weeks' gestation) or ELBW (<1,000 g) in 1997 in the state of Victoria, Australia. A comparison group of 173 of 199 children born full term and normal birth weight (FT/NBW) were randomly selected matching for birth hospital, expected due date, gender, mother's country of birth, and health insurance status. Participants were assessed at 8 years of age on subtests from the Test of Everyday Attention for Children (TEA-Ch) and the Wechsler Intelligence Scale for Children-4th Edition (WISC-IV). Measures of selective attention, sustained attention, attention encoding, and executive attention (inhibition, shifting attention, and divided attention) were administered. To assess behavioral elements of inattention, the primary caregiver completed the Behavior Rating Inventory of Executive Function (BRIEF) and the Conners' ADHD/DSM-IV Scale (CADS-P). The EP/ELBW group performed more poorly across all cognitive and behavioral measures than the FT/NBW group, with the exception of inhibition. The EP/ELBW group also had significantly elevated rates of impairment in selective, sustained, shifting and divided attention, as well as attention deficit hyperactivity disorder (ADHD) symptoms. No significant gender or gradient effects (e.g., <26 weeks' gestation vs. ≥ 26 weeks' gestation) were identified. Neonatal medical factors were not strong predictors of attention, although necrotizing enterocolitis (NEC) and cystic periventricular leukomalacia (PVL) were independent predictors of selective attention. In conclusion, our comprehensive assessment of attention provides strong evidence that children born EP/ELBW are at increased risk for attentional impairments, and as such, this population should be monitored closely during early and middle childhood with a focus on attention functioning.

Season of birth and childhood intelligence: Findings from the Aberdeen Children of the 1950s cohort study

BACKGROUND

In this study, 2 main hypotheses have been put forward to explain the variation in childhood intelligence or school performance by season of birth. In the first hypothesis, it is suggested that it is due to school policy concerning school entry, whereas the second suggests that a seasonally patterned exposure such as temperature, maternal nutrition, or infection during critical periods of brain development have a lasting effect on intelligence.

AIMS

To determine whether childhood performance on tests of different domains of intelligence is patterned by season of birth and to examine possible mechanisms for any associations.

SAMPLE

12,150 individuals born in Aberdeen, Scotland between 1950 and 1956.

METHODS

Birth cohort study in which the variation in different domains of childhood intelligence measured at ages 7, 9, and 11 by season of birth were examined.

RESULTS

Reading ability at age 9 and arithmetic ability at age 11 varied by season of birth, with lowest scores among those born in autumn or early winter (September-December) and highest scores among those born in later winter or spring (February-April); p=.002 for joint sine-cosine functions for reading ability at age 9 and p=.05 for sine-cosine function for arithmetic ability at age 11. The child's perception and understanding of pictorial differences at age 7, verbal reasoning at 11, and English language ability at 11 did not vary by season of birth. Age at starting primary school and age relative to class peers were both associated with the different measurements of childhood intelligence and both attenuated the association between month of birth and reading ability at age 9 and arithmetic ability at age 11 towards the null. Both adjusted and unadjusted differences in reading ability at age 9 and arithmetic ability at age 11 between those born from September to December compared with other times of the year were less than 0.1 of a standard deviation of the test scores. Ambient temperature around the time of conception, during gestation, and around the time of birth did not affect intelligence.

CONCLUSION

Any variation in mean childhood intelligence by season of birth is weak and largely explained by age at school entry and age relative to class peers.

Late-preterm birth and its association with cognitive and socioemotional outcomes at 6 years of age

INTRODUCTION

Late-preterm birth (34-36 weeks' gestation) has been associated with a risk for long-term cognitive and socioemotional problems. However, many studies have not incorporated measures of important contributors to these outcomes, and it is unclear whether effects attributed to gestational age are separate from fetal growth or its proxy, birth weight for gestational age.

METHOD

Data came from a study of low- and normal-weight births sampled from urban and suburban settings between 1983 and 1985 (low birth weight, n = 473; normal birth weight; n = 350). Random sampling was used to pair singletons born late-preterm with a term counterpart whose birth weight z score was within 0.1 SD of his or her match (n = 168 pairs). With random-effects models, we evaluated whether pairs differed in their IQ scores and teacher-reported behavioral problems at the age of 6 years.

RESULTS

In adjusted models, late-preterm birth was associated with an increased risk of full-scale (adjusted odds ratio [aOR]: 2.35 [95% confidence interval (CI): 1.20-4.61]) and performance (aOR: 2.04 [95% CI: 1.09-3.82]) IQ scores below 85. Late-preterm birth was associated with higher levels of internalizing and attention problems, findings that were replicated in models that used thresholds marking borderline or clinically significant problems (aOR: 2.35 [95% CI: 1.28-4.32] and 1.76 [95% CI: 1.04-3.0], respectively).

CONCLUSIONS

Late-preterm birth is associated with behavioral problems and lower IQ at the age of 6, independent of maternal IQ, residential setting, and sociodemographics. Future research is needed to investigate whether these findings result from a reduction in gestational length, in utero (eg, obstetric complications) or ex-utero (eg, neonatal complications) factors marked by late-preterm birth, or some combination of these factors.

Development of executive function and attention in preterm children: a systematic review

We report on a systematic review of studies of executive function and attention in preterm children. Using meta-analysis, we confirm this is an area of weakness for preterm children, and show that the extent of difficulties is influenced by gestational age (GA), age at test, and skill under investigation. Effect size for selective and sustained attention and inhibition is related to GA. For studies with mean GA > or = 26 weeks, selective attention skills catch up with age, phonemic fluency skills are increasingly delayed, and ongoing deviance is shown for shifting skills (when assessed with specific measures). Implications for research and practice are discussed.

No evidence of genetic mediation in the association between birthweight and academic performance in 2,413 Danish adolescent twin pairs

Evidence of a positive association between birthweight and IQ has been established in several studies. Analyses of within twin pair differences in birthweight and IQ have been used to shed light on the basis of the association. The strength of this approach is the possibility of controlling for both unmeasured common childhood-environmental factors as well as genetic factors shared by the co-twins. Two twin studies suggest the existence of genetic mediation between birthweight and IQ, that is, common genetic factors influence both fetal growth and IQ in childhood, while two other twin studies find no evidence of such mediation. In the present study we use a large population-based national register study of 2,413 Danish twin-pairs from birth cohorts 1986-1990, of which we have zygosity information on 74%. We perform individual level as well as intra-pair analyses of birthweight and school achievements at age 16. For both sexes we observed a monotonic increase in academic performance with increasing percentiles of birthweight. However, we did not find that this association is due to genetic mediation.

Attentional networks efficiency in preterm children

Recent studies have reported specific executive and attentional deficits in preterm children. However, the majority of this research has used multidetermined tasks to assess these abilities, and the interpretation of the results lacks an explicit theoretical backdrop to better understand the origin of the difficulties observed. In the present study, we used the Child Attention Network Task (Child ANT; Rueda et al. 2004) to assess the efficiency of the alerting, orienting and executive control networks. We compared the performance of 25 preterm children (gestational age < or = 32 weeks) to 25 full-term children, all between 5(1/2) and 6(1/2) years of age. Results showed that, as compared to full-term children, preterm children were slower on all conditions of the Child ANT and had a specific deficit in executive control abilities. We also observed a significantly higher correlation between the orienting and executive control networks in the preterm group, suggesting less differentiation of these two networks in this population.

Prenatal psychosocial stress exposure is associated with subsequent working memory performance in young women

The aim of the present study was to examine the association between prenatal psychosocial stress exposure and subsequent prefrontal cortex-dependent working memory performance in human adults. Working memory performance was assessed using an item-recognition task under 10 mg hydrocortisone (cortisol) and placebo conditions in a sample of 32 healthy young women (mean age = 25 +/- 4.34 years) whose mothers experienced a major negative life event during their pregnancy (Prenatal Stress, PS group), and in a comparison group of 27 healthy young women (mean age = 24 +/- 3.4 years). The two groups did not differ in the placebo condition, however, subjects in the PS group showed longer reaction times after hydrocortisone administration compared with subjects in the comparison group (p = .02). These findings provide support for an association between prenatal stress exposure and the potential modulatory effect of cortisol on working memory performance in young adults, which may reflect compromised development of the prefrontal cortex in prenatal life.

The impact of early behavior disturbances on academic achievement in high school

BACKGROUND

Previous research has indicated that childhood behavioral disturbances predict lower scores on academic tests and curtail educational attainment. It is unknown which types of childhood behavioral problems are most likely to predict these outcomes.

METHODS

An ethnically diverse cohort was assessed at 6 years of age for behavioral problems and IQ and at 17 years of age for academic achievement in math and reading. Of the original cohort of 823 children, 693 (84%) had complete data. Multiple regressions were used to estimate associations of attention and internalizing and externalizing problems at age 6 and with math and reading achievement at age 17, adjusting for IQ and indicators of family socioeconomic status.

RESULTS

Adjusting for IQ, inner-city community, and maternal education and marital status, teacher ratings of attention, internalizing behavior, and externalizing problems at age 6 significantly predict math and reading achievement at age 17. When types of problems are examined simultaneously, attention problems predict math and reading achievement with little attenuation, whereas the influence of externalizing and internalizing problems is materially reduced and not significant.

CONCLUSIONS

Interventions that target attention problems at school entry should be tested as a potential avenue for improving educational achievement.

The risk for impaired learning-related abilities in childhood and educational attainment among adults born near-term

OBJECTIVE

To examine whether near-term births (NTB) and small-for-gestational-age (SGA) infants are at high risk for childhood learning-related problems and poor adult educational attainment, and whether poverty amplifies the adverse effects of NTB and SGA on those outcomes.

METHODS

A randomly selected birth cohort (n = 1,619) was followed into adulthood. IQ and learning abilities were measured in childhood and educational attainment was measured in adulthood.

RESULTS

NTB (n = 226) and SGA (n = 154) were associated with lower educational attainment mediated through learning-related abilities at age 7. Childhood poverty moderated the impact of NTB on educational attainment both directly and mediated through lower learning-related abilities. Poverty did not moderate the effect of SGA.

CONCLUSIONS

Poorer learning-related outcomes and educational attainment were not limited to children born very (<32 weeks) or extremely (<28 weeks) preterm, especially among those living in poverty. Targeted interventions such as remedial learning during childhood among NTB in poor families may yield higher educational attainment.

Roles of perinatal problems on adolescent antisocial behaviors among children born after 33 completed weeks: a prospective investigation

BACKGROUND

There is uncertainty about the extent to which mildly sub-optimal perinatal characteristics among individuals born near-term (>33 weeks of gestation) are associated with various subsequent childhood problems, including antisocial behavior. There is even more uncertainty about whether the pathway to antisocial behavior differs by gender.

METHODS

A sample of 1689 infants, born near-term, was followed from birth for over 30 years. Using structural equation modeling (SEM), the study evaluated hypothesized mechanisms linking perinatal problems to antisocial behavior, mediated through the following variables in early and later childhood: neurological abnormalities at age 1; hearing, speech, and language problems at age 3; cognitive function at age 4; and academic performance at age 7. Childhood problems were assessed by trained research clinicians, blind to perinatal status. An 'antisocial behavior' variable was created, based on retrospective self-report of six antisocial incidences assessed in adulthood.

RESULTS

Path coefficients showed that birthweight, head circumference, and Apgar scores were indirectly associated with antisocial behavior in the presence of one or more of the following: neurological abnormalities, abnormality in language, speech, and hearing, cognitive function, or academic performance. We found gender differences only in the associations between hearing and IQ and between language perception and IQ. Poor academic performance was associated with antisocial behavior in both boys and girls.

CONCLUSION

Our hypothesis, that perinatal problems may progress to antisocial behavior when mediated by various markers of early childhood problems, was confirmed. Adverse perinatal events need to be considered in identifying infants who are at risk for academic problems and antisocial behavior, even when the infant is born relatively close to term (i.e., >33 weeks). Poor academic performance, which is indirectly influenced by a variety of neurological and cognitive problems during the perinatal period, infancy, and early childhood appear to increase antisocial behavioral problems in both girls and boys.

Ketamine analgesia for inflammatory pain in neonatal rats: a factorial randomized trial examining long-term effects

Background

Neonatal rats exposed to repetitive inflammatory pain have altered behaviors in young adulthood, partly ameliorated by Ketamine analgesia. We examined the relationships between protein expression, neuronal survival and plasticity in the neonatal rat brain, and correlated these changes with adult cognitive behavior.

Methods

Using Western immunoblot techniques, homogenates of cortical tissue were analyzed from neonatal rats 18–20 hours following repeated exposure to 4% formalin injections (F, N = 9), Ketamine (K, 2.5 mg/kg × 2, N = 9), Ketamine prior to formalin (KF, N = 9), or undisturbed controls (C, N = 9). Brain tissues from another cohort of rat pups (F = 11, K = 12, KF = 10, C = 15) were used for cellular staining with Fos immunohistochemistry or FluoroJade-B (FJB), followed by cell counting in eleven cortical and three hippocampal areas. Long-term cognitive testing using a delayed non-match to sample (DNMS) paradigm in the 8-arm radial maze was performed in adult rats receiving the same treatments (F = 20, K = 24, KF = 21, C = 27) in the neonatal period.

Results

Greater cell death occurred in F vs. C, K, KF in parietal and retrosplenial areas, vs. K, KF in piriform, temporal, and occipital areas, vs. C, K in frontal and hindlimb areas. In retrosplenial cortex, less Fos expression occurred in F vs. C, KF. Cell death correlated inversely with Fos expression in piriform, retrosplenial, and occipital areas, but only in F. Cortical expression of glial fibrillary acidic protein (GFAP) was elevated in F, K and KF vs. C. No significant differences occurred in Caspase-3, Bax, and Bcl-2 expression between groups, but cellular changes in cortical areas were significantly correlated with protein expression patterns. Cluster analysis of the frequencies and durations of behaviors grouped them as exploratory, learning, preparatory, consumptive, and foraging behaviors. Neonatal inflammatory pain exposure reduced exploratory behaviors in adult males, learning and preparatory behaviors in females, whereas Ketamine ameliorated these long-term effects.

Conclusion

Neuroprotective effects of Ketamine attenuate the impaired cognitive behaviors resulting from pain-induced cell death in the cortical and hippocampal fields of neonatal rats. This cell death was not dependent on the apoptosis associated proteins, but was correlated with glial activation.

Impaired executive functioning in young adults born very preterm

Individuals born very preterm (VPT) are at increased risk of perinatal brain injury and long-term cognitive and behavioral problems. Executive functioning, in particular, has been shown to be impaired in VPT children and adolescents. This study prospectively assessed executive function in young adults who were born VPT (<33 weeks of gestation) [n = 61; mean age, 22.25 (+/-1.07) years; range, 20.62-24.78 years] and controls [n = 64; mean age, 23.20 (+/-1.48) years; range, 19.97-25.46 years]. Tests used comprised the Wechsler Abbreviated Scale of Intelligence (WASI), the Hayling Sentence Completion Test (HSCT), the Controlled Oral Word Association Test (COWAT), the Animal and Object test, the Trail-Making Test (TMT), and the Test of Attentional Performance (TAP). VPT participants showed specific executive function impairments in tasks involving response inhibition and mental flexibility, even when adjusting for IQ, gender, and age. No significant associations were observed between executive function test scores and perinatal variables or neonatal ultrasound classification. The results suggest that, although free from major physical disability, VPT young adults perform worse than controls on tasks involving selective aspects of executive processing, such as mental flexibility and response inhibition.

Mental health and social competencies of 10- to 12-year-old children born at 23 to 25 weeks of gestation in the 1990s: a Swedish national prospective follow-up study

OBJECTIVE

We investigated a national cohort of extremely immature children with respect to behavioral and emotional problems and social competencies, from the perspectives of parents, teachers, and children themselves.

METHODS

We examined 11-year-old children who were born before 26 completed weeks of gestation in Sweden between 1990 and 1992. All had been evaluated at a corrected age of 36 months. At 11 years of age, 86 of 89 survivors were studied and compared with an equal number of control subjects, matched with respect to age and gender. Behavioral and emotional problems, social competencies, and adaptive functioning at school were evaluated with standardized, well-validated instruments, including parent and teacher report questionnaires and a child self-report, administered by mail.

RESULTS

Compared with control subjects, parents of extremely immature children reported significantly more problems with internalizing behaviors (anxiety/depression, withdrawn, and somatic problems) and attention, thought, and social problems. Teachers reported a similar pattern. Reports from children showed a trend toward increased depression symptoms compared with control subjects. Multivariate analysis of covariance of parent-reported behavioral problems revealed no interactions, but significant main effects emerged for group status (extremely immature versus control), family function, social risk, and presence of a chronic medical condition, with all effect sizes being medium and accounting for 8% to 12% of the variance. Multivariate analysis of covariance of teacher-reported behavioral problems showed significant effects for group status and gender but not for the covariates mentioned above. According to the teachers' ratings, extremely immature children were less well adjusted to the school environment than were control subjects. However, a majority of extremely immature children (85%) were functioning in mainstream schools without major adjustment problems.

CONCLUSIONS

Despite favorable outcomes for many children born at the limit of viability, these children are at risk for mental health problems, with poorer school results.

Growth status related to brain responses, nutrition, home environment, and behavior in infants and toddlers

To investigate whether growth status in infants and toddlers affects processes involved in speech perception and discrimination, cortical event-related potentials (ERPs) to consonant-vowel syllables were recorded from 48 healthy babies: 26 low in growth status (LGS, < 25 th percentile in growth measures) and from 22 normal in growth status (NGS, 25t--75 th percentile in growth measures). Food records indicated no significant differences in the amounts of various nutrients consumed in the two groups, but LGS babies consumed slightly more of most nutrients than NGS babies. In response to speech stimuli (either /pa/ or /ba/ presented with 20 and 80% randomized occurrence), brain ERPs showed two prominent post-stimulus components: a large positive wave peaking at about 484 msec and a negative but positive going slow wave (SW) between 867 and 1199 msec. Principal components analysis followed by promax rotation revealed four additional important components. Maximum peak and latency values-for these components showed that NGS and LGS babies differed from one another on all measures in either amplitude, latency, or both. Comparing the two groups of babies, only the LGS group demonstrated a deficit in the phonetic discrimination of speech sounds. The growth deficiencies of the LGS group could not be attributed to the lack of an adequate diet. These negative findings are present in babies generally considered to be healthy (lowest 10-25% in growth measures). This underscores the need for research examining in more detail the relationship between growth status and cognitive growth.

Effect of community of residence on neurobehavioral development in infants and young children in a flower-growing region of Ecuador

OBJECTIVE

In this study we compared neurobehavioral development in Ecuadoran children living in two communities with high potential for exposure to organophosphate (OP) and carbamate pesticides to that of children living in a community with low potential for exposure.

METHODS

Women residing in the study communities who had a child 3-61 months of age completed a questionnaire about maternal and child health and sociodemographic characteristics. The Ages and Stages Questionnaire (ASQ) was administered to each child (n = 283). Growth measurements and a hemoglobin finger-prick blood test were obtained. We used multiple linear regressions to evaluate associations between community of residence and delayed development, adjusting for child health status and other characteristics of the home environment.

RESULTS

Children 3-23 months of age who resided in high-exposure communities scored lower on gross motor (p = 0.002), fine motor (p = 0.06), and socioindividual (p-value = 0.02) skills, compared with children in the low-exposure community. The effect of residence in a high-exposure community on gross motor skill development was greater for stunted children compared with non-stunted children (p = < 0.001) in the same age group of 3-23 months. Children 24-61 months of age residing in the high-exposure communities scored significantly lower on gross motor skills compared with children of similar ages residing in the low-exposure community (p = 0.06).

CONCLUSIONS

Residence in communities with high potential for exposure to OP and carbamate pesticides was associated with poorer neurobehavioral development of the child even after controlling for major determinants of delayed development. Malnourished populations may be particularly vulnerable to neurobehavioral effects of pesticide exposure.

Sex Differences in the Pathway from Low Birth Weight to Inattention/hyperactivity

Inattention/hyperactivity is a childhood outcome of low birth weight. However, the mechanisms by which low birth weight leads to inattention/hyperactivity are unclear. This study examined arousal, activation, motor speed, and motor coordination as possible mechanisms, attending to sex differences. 823 children (400 males) from Detroit and surrounding suburbs were assessed with the Child Behavior Checklist and the Teacher Report Form and completed experimental tasks to assess vigilance and activation (Continuous Performance Test signal detection parameters) and motor output speed and control (Grooved Pegboard) at 6 years of age. The relationship between birth weight and inattention/hyperactivity was slightly, but not significantly, stronger for boys than for girls. Arousal, motor speed, and motor coordination significantly partially mediated the relationship between birth weight and inattention/hyperactivity for boys and girls. Moderated mediation was found for the pathway between motor coordination and inattention/hyperactivity such that this relationship was stronger for boys than for girls. Sex differences in the associated features of attention symptoms may reflect partially distinct etiological pathways.

Gestational age and birth weight in relation to school performance of 10-year-old children: a follow-up study of children born after 32 completed weeks

BACKGROUND

Children born extremely premature (<28 weeks) or with a very low birth weight (<1500 g) have a poorer school performance than children born at term with a normal birth weight. Much less is known about children of higher gestational ages and birth weights. We studied gestational age after 32 completed weeks and birth weight in relation to the child's school performance at the age of 10 years.

METHODS

We performed a follow-up study of 5319 children born between January 1990 and June 1992. We got the information on birth weight and gestational age from birth registration forms; when the children were between 9 and 11 years of age, we gathered information about their school performance (reading, spelling, and arithmetic) from questionnaires completed by the parents and the children's primary school teachers.

RESULTS

The association between birth weight and reading, as well as spelling and arithmetic disabilities, showed a graded relationship, with children who weighed <2500 g having the highest risks. Even children who weighed between 3000 and 3499 g had an increased risk of all 3 learning disabilities compared with children who weighed between 3500 and 4000 g. This association persisted after adjustment for potential cofounders and when the analyses were restricted to children born at term (39-40 weeks of gestation), suggesting that the association could not be explained by a low gestational age. Compared with children born at term, reading and spelling difficulties were more often found among children born at gestational age 33 to 36 weeks and 37 to 38 weeks, whereas there was no relation between gestational age and arithmetic difficulties.

CONCLUSIONS

Gestational age and birth weight were associated with school performance in the 10-year-old child and the association extended into the reference range of both birth weight and gestational age.

Association between intelligence quotient scores and extremely low birth weight in school-age children

BACKGROUND

Extremely low birth weight (ELBW) has been associated with poor cognitive development in children. We performed this research to establish the association between ELBW and the influence of biological and socioeconomic factors in the intelligence quotient (IQ) score in school-age children.

METHODS

This study comprised 184 children with mean and standard deviation of 6.9 +/- 0.8 years of age. The children were divided into four groups based on their birth weight as follows: group A (n = 25), < or =1000 g; group B (n = 52), 1001-1500 g; group C (n = 66), 1501-2500 g; and group D (n = 41), > or =2501 g. The Stanford-Binet after the Terman-Merril Intelligence Scale was used to determine IQ scores.

RESULTS

Mean and standard deviation (SD) of IQ values were 95.3 +/- 11.3 for group A, 103.1 +/- 14.4 for group B, 105.1 +/- 12.3 for group C, and 106.8 +/- 11.7 for group D (p = 0.003). Frequencies of children with scores below normal distribution were the following: 28% in group A; 10% in group B; 15% in group C, and 5% in group D (chi(2) = 0.04). Bronchopulmonary dysplasia and parental education were associated with lower IQ scores (p <0.05).

CONCLUSIONS

IQ scores of children born with ELBW were significantly lower when compared to children born with a higher birth weight. Additional studies are important to determine whether these neurodevelopmental delays persist into adulthood, and whether there are additional factors associated with catch-up and recovery.

Neurodevelopmental outcome of bronchopulmonary dysplasia

Children born very preterm are vulnerable for long-term cognitive, educational, and behavioral impairments; bronchopulmonary dysplasia (BPD) is an additional risk factor which exacerbates these problems. As a population, children with BPD exhibit low average IQ, academic difficulties, delayed speech and language development, visual-motor integration impairments, and behavior problems. Neuropsychological studies are sparse, but there is some evidence that children with BPD also display attention problems, memory and learning deficits, and executive dysfunction. BPD does not appear to be associated with a specific neuropsychological impairment but rather a global impairment.

The pregnant spontaneously hypertensive rat as a model of asymmetric intrauterine growth retardation and neurodevelopmental delay

INTRODUCTION

Hypertension in pregnancy and vascular placental insufficiency are considered common pathogenic factors in human intrauterine growth retardation (IUGR). IUGR neonates experience higher mortality, and the surviving infants have a higher incidence of neurological and intellectual impairment.

METHODS

To mimic this condition, we used pregnant spontaneously hypertensive rats (SHR) and performed biometric measurements on Embryonic Day 20, postnatal developmental reflexes, and locomotor activity evaluations.

RESULTS

SHR fetuses had significant decreased body weight compared to the Wistar-Kyoto control fetuses (1.51+/-0.02 g vs. 2.05+/-0.01 g, respectively; p<0.0001), and were relatively microcephalic (2.86+/-0.04 cm vs. 3.3+/-0.03 cm, respectively; p<0.0001). Their cephalization index (head circumference/body weight) was increased (1.88+/-0.03 vs. 1.62+/-0.02, respectively; p<0.0001), indicating a "brain-sparing" process. The disproportional ratio indicated that the IUGR type in this model is asymmetric. The SHR pups exhibited a significant (p<0.04) neurodevelopmental delay in the acquisition of neonatal reflexes (righting, negative geotaxis, placing), but they spontaneously caught up with the control pups after approximately 10 days. On Day 30, the SHR pups exhibited significantly increased walking speed and distance and spent less time in quadrant than the controls (p<0.002).

CONCLUSION

We speculate that the model of pregnant SHR closely simulate human IUGR caused by hypertension in pregnancy and should enable investigation of mechanisms of hypertension-mediated placenta-vascular injury as well as provide a system for preclinical evaluations of future preventive neuroprotective treatments.

Birthweight and cognitive development during childhood

OBJECTIVES

Low birthweight has been reported to be associated with lower IQ at school age. Further, some evidence suggests that the association extends across the range of normal birthweights. This study assessed the relationship of birthweight to cognitive development in the Port Pirie birth cohort.

METHODS

Of 723 singleton live births recruited into a prospective birth cohort study, 601, 548, 494 and 375 children were followed at ages 2, 4, 7 and 11-13 years, respectively. The children's developmental status was assessed using the Bayley Scales of Infant Development at age 2 years, the McCarthy Scales of Children's Abilities at age 4 years, and the revised Wechsler Intelligence Scale for Children at ages 7 and 11-13 years. The association between birthweight and cognitive function was assessed with multiple linear regression, adjusting for a wide range of possible confounders.

RESULTS

The mean birthweight was 3386 g (SD: 517). There was a statistically significant association between birthweight and cognitive performance at age 2 years (adjusted deficit: 0.97 points per 100 g lighter; 95% CI: 0.4-1.5), but the magnitude of this association gradually decreased and became statistically non-significant at later childhood.

CONCLUSIONS

The relationship between birthweight and cognitive development becomes progressively attenuated at increasing age. At older ages, socioenvironmental factors appear to play an increasingly important part in children's cognitive development.

Early life predictors of childhood intelligence: findings from the Mater-University study of pregnancy and its outcomes

Growing evidence linking childhood intelligence with adult health outcomes suggests a need to identify predictors of this psychological characteristic. In this study, we have examined the early life determinants of childhood intelligence in a population-based birth cohort of individuals born in Brisbane, Australia between 1981 and 1984. In univariable analyses, family income in the year of birth, maternal and paternal education, maternal age at birth, maternal ethnicity, maternal smoking during pregnancy, duration of labour, birthweight, breast feeding and childhood height, and body mass index were all associated with intelligence at age 14. In multivariable analyses, the strongest and most robust predictors of intelligence were family income, parental education and breast feeding, with these three variables explaining 7.5% of the variation in intelligence at age 14. Addition of other variables added little further explanatory power. Our results demonstrate the importance of indicators of socio-economic position as predictors of intelligence, and illustrate the need to consider the role of such factors in generating the association of childhood intelligence with adult disease risk.

Early precursors of low attention and hyperactivity in a preterm sample at age four

The increased numbers of low birth weight (LBW) survivors has raised questions about the direct association between LBW and later diagnosis of Attention Deficit Hyperactivity Disorder (ADHD) in early childhood. A longitudinal data set was used to determine the relationship among perinatal morbidity and medical and neurological status during the toddler period (18 and 30 months) with lower attention and higher activity, cardinal features of ADHD at age 4. The sample of 39 full term and 149 preterm infants were recruited at birth. Infants were assigned to 1 of 5 groups based on perinatal morbidity. Medical and neurological status were classified as normal, suspect, or abnormal at 18 and 30 months. At age 4, five measures of attention and activity were gathered from parents and independent examiners. Multivariate analysis of variance (MANOVA) showed significant effects of perinatal morbidity, birth weight, gestational age, gender, socioeconomic status at infancy, and toddler medical and neurological status with lower attention and higher activity at age 4. Prematurity, perinatal illness, and later medical status are early markers for preschool behaviors associated with clinical diagnosis of ADHD.

10-year research update review: the epidemiology of child and adolescent psychiatric disorders: II. Developmental epidemiology

OBJECTIVE

To describe the growth of developmental epidemiology in the past decade and to illustrate it with examples of recent studies.

METHOD

A review of publications on developmental epidemiology in the past 10 years and a discussion of some key examples.

RESULTS

The authors describe how the interaction between developmental psychopathology and psychiatric epidemiology has produced developmental epidemiology, the study of patterns of distribution of psychiatric disorders in time as well as in space. They give two examples of the kinds of questions that developmental epidemiology can help to answer: (1) Is the prevalence of autism increasing? Does the use of vaccines explain the increase? (2) Is there an epidemic of child and adolescent depression? Finally, they describe two areas of science that are beginning to inform developmental epidemiology: molecular genetics and the use of biological measures of stress.

CONCLUSIONS

While child and adolescent psychiatric epidemiology continues, as described in the first of these reviews, to address questions of prevalence and burden, it has also expanded into new areas of research in the past decade. In the next decade, longitudinal epidemiological data sets with their rich descriptive data on psychopathology and environmental risk over time and the potential to add biological measures will provide valuable resources for research into gene-environment correlations and interactions.