Latent Class Analysis of Neurodevelopmental Deficit After Exposure to Anesthesia in Early Childhood

INTRODUCTION

Although some studies have reported an association between early exposure to anesthesia and surgery and long-term neurodevelopmental deficit, the clinical phenotype of children exposed to anesthesia is still unknown.

METHODS

Data were obtained from the Western Australian Pregnancy Cohort Study (Raine) with neuropsychological tests at age 10 years measuring language, cognition, motor function, and behavior. Latent class analysis of the tests was used to divide the cohort into mutually exclusive subclasses of neurodevelopmental deficit. Multivariable polytomous logistic regression was used to evaluate the association between exposure to surgery and anesthesia and each latent class, adjusting for demographic and medical covariates.

RESULTS

In our cohort of 1444 children, latent class analysis identified 4 subclasses: (1) Normal: few deficits (n=1135, 78.6%); (2) Language and Cognitive deficits: primarily language, cognitive, and motor deficits (n=96, 6.6%); (3) Behavioral deficits: primarily behavioral deficits, (n=151, 10.5%); and (4) Severe deficits: deficits in all neuropsychological domains (n=62, 4.3%). Language and cognitive deficit group children were more likely to have exposure before age 3 (adjusted odds ratio [aOR], 2.11; 95% confidence interval [CI], 1.17-3.81), whereas a difference in exposure was not found between Behavioral or Severe deficit children (aOR, 1.00; 95% CI, 0.58-1.73, and aOR, 0.85; 95% CI, 0.34-2.15, respectively) and Normal children.

CONCLUSIONS

Our results suggest that in evaluating children exposed to surgery and anesthesia at an early age, the phenotype of interest may be children with deficits primarily in language and cognition, and not children with broad neurodevelopmental delay or primarily behavioral deficits.

Prenatal methylmercury exposure and language delay at three years of age in the Norwegian Mother and Child Cohort Study

Prenatal methylmercury (MeHg) exposure and its possible neurodevelopmental effects in susceptible children are of concern. Studies of MeHg exposure and negative health outcomes have shown conflicting results and it has been suggested that co-exposure to other contaminants and/or nutrients in fish may confound the effect of MeHg. Our objective was to examine the association between prenatal exposure to MeHg and language and communication development at three years, adjusting for intake of fish, n-3 long chain polyunsaturated fatty acids (n-3 LCPUFAs) and co-exposure to dioxins and dioxin like polychlorinated biphenyls (dl-PCBs). We used data from the Norwegian Mother and Child Cohort Study (MoBa) collected between 2002 and 2008. The study sample consisted of 46,750 mother-child pairs. MeHg exposure was calculated from reported fish intake during pregnancy by a FFQ in mid-pregnancy. Children's language and communication skills were measured by maternal report on the Dale and Bishop grammar rating and the Ages and Stages communication scale (ASQ). We estimated odds ratios (OR) and 95% confidence intervals (CI) using logistic regressions. Median MeHg exposure was 1.3μg/day, corresponding to 0.14μg/kgbw/week. An exposure level above the 90th percentile (>2.6μg/day, >0.29μg/kgbw/week) was defined as the high MeHg exposure. Results indicated an association between high MeHg exposure and unintelligible speech with an adjusted OR 2.22 (1.31, 3.72). High MeHg exposure was also associated with weaker communication skills adjusted OR 1.33 (1.03, 1.70). Additional adjustment for fish intake strengthened the associations, while adjusting for PCBs and n-3 LCPUFA from diet or from supplements had minor impact. In conclusion, significant associations were found between prenatal MeHg exposure above the 90th percentile and delayed language and communication skills in a generally low exposed population.

Prenatal chemical exposures and child language development

The goal of this review is to summarize the evidence that prenatal and/or early postnatal exposure to certain chemicals, both manmade (insulating materials, flame retardants, pesticides) and naturally occurring (e.g., lead, mercury), may be associated with delays or impairments in language development. We focus primarily on a subset of more extensively studied chemicals-polychlorinated biphenyls (PCBs), lead, and methyl mercury-for which a reasonable body of literature on neurodevelopmental outcomes is available. We also briefly summarize the smaller body of evidence for other chemicals including polybrominated diphenyl ether flame retardants (PBDEs) and organophosphate pesticides. Very few studies have used specific assessments of language development and function. Therefore, we included discussion of aspects of cognitive development such as overall intellectual functioning and verbal abilities that rely on language, as well as aspects of cognition such as verbal and auditory working memory that are critical underpinnings of language development. A high percentage of prospective birth cohort studies of PCBs, lead, and mercury have reported exposure-related reductions in overall IQ and/or verbal IQ that persist into middle or late childhood. Given these findings, it is important that clinicians and researchers in communication sciences and disorders are aware of the potential for environmental chemicals to impact language development.

LEARNING OUTCOMES

The goal of this review is to summarize the evidence that prenatal and/or early postnatal exposure to certain chemicals may be associated with delays or impairments in language development. Readers will gain an understanding of the literature suggesting that early exposure to polychlorinated biphenyls (PCBs), lead, and mercury may be associated with decrements in cognitive domains that depend on language or are critical for language development. We also briefly summarize the smaller body of evidence regarding polybrominated diphenyl ether flame retardants (PBDEs) and organophosphate pesticides. Very few studies of exposure to these chemicals have used specific assessments of language development; thus, further investigation is needed before changes in clinical practice can be suggested.

Milestone achievement and neurodevelopment of rural Amazonian toddlers (12 to 24 months) with different methylmercury and ethylmercury exposure

Neurological outcomes (Gesell development schedules [GDS]), age of walking, and age of talking were studied in 299 toddlers (12 to 24 mo) in relation to environmental (fish consumption and tin mining) exposure. Exposure to fish methylmercury (MeHg) consumption and iatrogenic ethylmercury (EtHg) in Thimerosal-containing vaccines (TCV) was quantified in toddlers from two rural villages (n = 91, Itapuã; n = 218, Bom Futuro) respectively populated by fishers and cassiterite miners. Median total hair Hg (HHg) concentrations of infants from Itapuã (3.5 μg/g) were significantly higher than those of infants from Bom Futuro (2.2 μg/g). Median EtHg exposure from TCV was also significantly higher in toddlers from Itapuã (137.5 μg) than in those from Bom Futuro (112.5 μg). There were no significant differences between groups for any of the Gesell schedules; however, there were proportionally more compromised toddlers (GDS < 70) in Itapuã than Bom Futuro. Median age of talking was not statistically different but median age of walking was significantly higher in Bom Futuro. In toddlers from both villages, of fishers and miners, HHg concentrations were significantly correlated with family fish consumption. A logistic regression model was applied to all infants after classification into two groups: above or below the median Gesell schedules. Overall, there was no distinctive pattern of neurodevelopment associated with either HHg or EtHg exposure; however, nutritional status was significantly associated with GDS. In conclusion, milestone achievement was delayed in toddlers from tin-ore mining communities. Despite significantly higher exposure to both forms of organic Hg (MeHg from maternal fish consumption, and EtHg from TCV) in toddlers from the fishing village, significant differences were seen only among the proportions of most severely affected toddlers (GDS < 70).

Deviant ERP response to spoken non-words among adolescents exposed to cocaine in utero

Concern for the impact of prenatal cocaine exposure (PCE) on human language development is based on observations of impaired performance on assessments of language skills in these children relative to non-exposed children. We investigated the effects of PCE on speech processing ability using event-related potentials (ERPs) among a sample of adolescents followed prospectively since birth. This study presents findings regarding cortical functioning in 107 prenatally cocaine-exposed (PCE) and 46 non-drug-exposed (NDE) 13-year-old adolescents. PCE and NDE groups differed in processing of auditorily presented non-words at very early sensory/phonemic processing components (N1/P2), in somewhat higher-level phonological processing components (N2), and in late high-level linguistic/memory components (P600). These findings suggest that children with PCE have atypical neural responses to spoken language stimuli during low-level phonological processing and at a later stage of processing of spoken stimuli.

Valproic acid: long-term effects on children exposed in utero

(1) Numerous follow-up studies of pregnancies in women with epilepsy show that valproic acid is more teratogenic than other antiepileptics. The risk of malformations increases with doses above 1000 mg/day; (2) Malformations associated with valproic acid include neural tube defects in 1-2% of exposed children, as well as urogenital, craniofacial and digital abnormalities. Cardiac disorders and limb defects have also been reported; (3) Convergent results of several cohort studies show that exposure to valproic acid in utero has detrimental effects on intelligence, language and behavior, which appear in school-age children; (4) In practice, the use of valproic acid should be avoided throughout pregnancy, as well as by women of childbearing age not using effective contraception. If a woman is planning pregnancy, the choice of valproic acid should be reassessed with the patient. If valproic acid therapy is maintained, the minimum effective daily dose should be determined and folic acid supplementation initiated.

Estimating the neurocognitive effects of an early intervention program for children with prenatal alcohol exposure

BACKGROUND

Animal studies suggest that early intervention in pups exposed heavily to ethanol in utero can mitigate their neurocognitive damage. No human studies on this promising mechanism exists.

METHODS

Breaking the Cycle is an early intervention program for drug-and alcohol addicted mothers and their young children. We compared BSID-III scores between infants heavily exposed to ethanol and a group exposed only to drugs of abuse, mainly cocaine. Both groups benefited from all aspects of our early intervention program.

RESULTS

The two groups did not differ in any aspect of the BSID-III. These data are in contradistinction to the damage seen in heavily ethanol- exposed infants not benefiting from early intervention.

CONCLUSIONS

This pilot suggests that early intervention may mitigate some of the well described damages caused by heavy in utero alcohol exposure.

Cognitive development and low-level lead exposure in poly-drug exposed children

The impact of early postnatal lead exposure measured at age 4 on children's IQ and academic achievement at and 11 years of age was examined. The sample consisted of 278 inner-city, primarily African American children who were polydrug exposed prenatally. Regression analyses indicated a linear effect of lead exposure on outcomes and no moderating effects of polydrug exposure. An IQ loss of about 4.1-5.4 Full Scale IQ points was estimated for each 10 microg/dL increase in blood lead level at ages 4, 9, and 11 years as a function of blood lead level at age 4. Decrements in scores on tests of non-verbal reasoning were consistently associated with higher lead levels at age 4, while verbal decrements became apparent only at age 11. Lower reading summary scores at 9 and 11 years were consistently associated with higher lead exposure, while decrements in mathematics were not apparent until 11 years. Subgroup analyses on children with blood lead levels <10 microg/dL showed detrimental lead effects even at the 5 microg/dL level, providing additional evidence of adverse effects occurring at blood lead levels below the current 10 microg/dL public health blood lead action level.

Neonatal nicotine exposure impairs nicotinic enhancement of central auditory processing and auditory learning in adult rats

Children of women who smoke cigarettes during pregnancy display cognitive deficits in the auditory-verbal domain. Clinical studies have implicated developmental exposure to nicotine, the main psychoactive ingredient of tobacco, as a probable cause of subsequent auditory deficits. To test for a causal link, we have developed an animal model to determine how neonatal nicotine exposure affects adult auditory function. In adult control rats, nicotine administered systemically (0.7 mg/kg, s.c.) enhanced the sensitivity to sound of neural responses recorded in primary auditory cortex. The effect was strongest in cortical layers 3 and 4, where there is a dense concentration of nicotinic acetylcholine receptors (nAChRs) that has been hypothesized to regulate thalamocortical inputs. In support of the hypothesis, microinjection into layer 4 of the nonspecific nAChR antagonist mecamylamine (10 microM) strongly reduced sound-evoked responses. In contrast to the effects of acute nicotine and mecamylamine in adult control animals, neither drug was as effective in adult animals that had been treated with 5 days of chronic nicotine exposure (CNE) shortly after birth. Neonatal CNE also impaired performance on an auditory-cued active avoidance task, while having little effect on basic auditory or motor functions. Thus, neonatal CNE impairs nicotinic regulation of cortical function, and auditory learning, in the adult. Our results provide evidence that developmental nicotine exposure is responsible for auditory-cognitive deficits in the offspring of women who smoke during pregnancy, and suggest a potential underlying mechanism, namely diminished function of cortical nAChRs.

Infant joint attention skill and preschool behavioral outcomes in at-risk children

This study examined whether infant joint attention (JA) skills predicted social behaviors in a sample of at-risk preschool children (n = 30) with a history of prenatal exposure to cocaine. JA behaviors were assessed with the Early Social and Communication Scales at 12, 15, and 18 months of age. Three classes of JA were measured: Initiating JA (IJA), Responding to JA (RJA), and Requests. Behavioral outcomes were measured at 36 months and included ratings of disruptive and withdrawn behaviors and social competence. JA behaviors were related to behavioral outcomes after controlling for language and cognitive ability. The functionally distinct uses of JA were differentially related to behavioral outcome. IJA negatively predicted disruptive behaviors, whereas Requests positively predicted disruptive behaviors. Infant RJA negatively predicted withdrawn behaviors and positively predicted social competence. These results are interpreted in the context of competing theories that attempt to explain variability in the expression of JA skills in the second year of life.

Epidemiology and etiology of autistic spectrum disorders difficult to determine

The epidemiology of the autistic spectrum disorders is changing. A clear increase in prevalence has been noted during the past 2 decades. What is less clear is the cause for this increase. Multiple factors appear to be responsible. The preponderance of evidence suggests most of the rise in incidence and prevalence is related to changes in diagnostic criteria and greater awareness on the part of both professionals and parents. Proposed theories of causation, which also seek to explain the increase in prevalence, have not been substantiated. Further research is needed to better determine the incidence and prevalence of these disorders and their etiologic factors.

Influence of prenatal cocaine exposure on early language development: longitudinal findings from four months to three years of age

The influence of prenatal cocaine exposure on children's language functioning was evaluated longitudinally at six time points from 4 months to 3 years of age. The Miami Prenatal Cocaine Study prospectively enrolled 476 full-term African-American infants at birth, categorized as cocaine-exposed (n = 253) or non-cocaine-exposed (n = 223) by maternal self-report and bioassays (maternal/infant urine, meconium). The Bayley Scales of Infant Development, scored using the Kent Scoring Adaptation for language, was administered at 4, 8, 12, 18, and 24 months. The Clinical Evaluation of Language Fundamentals-Preschool was administered at 3 years. In longitudinal analyses using Generalized Estimating Equations, cocaine-exposed children had lower overall language skills than non-cocaine-exposed children (D = -0.151; 95% CI = -0.269, -0.033; p =.012). Longitudinal findings remained stable after evaluation of potential confounding influences including other prenatal substance exposures and sociodemographic factors. Preliminary evidence also indicated possible mediation through an intermediary effect involving cocaine-associated deficits in fetal growth.

Longitudinal influence of prenatal cocaine exposure on child language functioning

The present study estimates the longitudinal effects of in utero cocaine exposure on language functioning at 3, 5 and 7 years of age in an urban sample of 443 full-term children (236 cocaine-exposed and 207 noncocaine-exposed) participating in the Miami Prenatal Cocaine Study. The sample was enrolled prospectively at birth, with documentation of prenatal drug exposure status through maternal interview and urine and meconium toxicology assays. Language functioning was measured at ages 3 and 5 years using the Clinical Evaluation of Language Fundamentals-Preschool (CELF-P) and at age 7 years using the Core Language Domain of the NEPSY: A Developmental Neuropsychological Assessment. Longitudinal Generalized Linear Model and Generalized Estimating Equations (GLM/GEE) analyses revealed an association between prenatal cocaine exposure and deficits in total language functioning after statistically controlling for child sex, visit age, prenatal exposure to alcohol, marijuana and tobacco and over 20 additional medical and sociodemographic covariates drawn from potentially confounding influences assessed at birth and follow-up visits (D=-0.17; 95% CI=-0.32, -0.03; P=.019). The link from prenatal cocaine exposure to later language deficits does not appear to be mediated by cocaine-associated deficits in birth weight, length or head circumference. Overall, the evidence tends to support an inference of a stable cocaine-specific effect on indicators of language functioning during early childhood through age 7 years.

Neurodevelopment of adopted children exposed in utero to cocaine: the Toronto Adoption Study

BACKGROUND

Published studies of children's neurodevelopment after in utero exposure to cocaine have not separated intrauterine from postnatal environmental effects as cocaine-using mothers cluster in low socioeconomic classes and have other risk factors.

METHODS

To overcome this limitation, a study was done to assess physical and neurodevelopmental characteristics of 52 children: 26 were adopted by parents who sought counselling in the Motherisk Program at the University of Toronto for prenatal cocaine exposure, and 26 were controls matched for maternal intelligence quotient (IQ), socioeconomic status and gestational age.

MAIN OUTCOME MEASURES

Head circumference, McCarthy General Cognitive Index (GCI) score, language performance and temperament tests.

RESULTS

The children in the study group had smaller head circumferences (34th versus 54th percentiles p = 0.009), lower McCarthy GCI scores (102.8 versus 114.2, p = 0.02), poorer receptive and expressive language performance on the Reynell test, and higher activity levels, less persistence and increased distractibility on temperament tests. On multivariate analysis, cocaine exposure was significantly (p = 0.001) associated with lower IQ and poorer language development independent of intrauterine growth retardation and other potential confounders.

INTERPRETATION

By controlling for postnatal environmental factors, this adoption study documents intrauterine developmental risks associated with cocaine exposure. Follow-up into school years is warranted to evaluate the extent of these effects.

Expressive language development of children exposed to cocaine prenatally: literature review and report of a prospective cohort study

It was hypothesized that prenatal exposure to cocaine and other substances would be related to delayed expressive language development. Speech and language data were available for 458 6-year olds (204 were exposed to cocaine). No significant univariate or multivariate differences by cocaine exposure group were observed. Classification and regression tree modeling was then used to identify language variable composites predictive of cocaine exposure status. Meaningful cut points for two language measures were identified and validated. Children with a type token ratio of less than 0.42 and with fewer than 97 word types were classified into a low language group. Low language children (n = 57) were more likely to be cocaine exposed (63.1%), with cocaine-exposed children 2.4 times more likely to be in the low language group compared with control children after adjustment for covariates. Prenatal cigarette, but not alcohol exposure, was also significantly related to expressive language delays.

Comparative study of the phonology of preschool children prenatally exposed to cocaine and multiple drugs and non-exposed children

Cocaine and multiple drug abuse among young adults has spawned research interest in fetal exposure and the sequela of that exposure during the formative developmental years. Previous study of the language development of exposed children has not specifically addressed phonological acquisition. In the present study, the speech of 25 children prenatally exposed to cocaine and multiple drugs was analyzed and compared to that of 25 children who were not prenatally exposed to determine if differences were evident in their phonological patterns. The children ranged in age from 22 months to 51 months. The number and type of phonological processes produced, number of utterances needed to produce a 50-word sample, number of unintelligible words produced, and Home Observation for Measurement of the Environment (HOME) scores were recorded and analyzed. The use of cocaine and multiple drugs during pregnancy was associated with an increase in the use of phonological processes.

The developmental implications of prenatal and/or postnatal crack cocaine exposure in preschool children: a preliminary report

Previous studies examining the development of prenatally cocaine-exposed children through 3 years of age have found no significant differences between exposed and control groups. This study explored the developmental correlates of prenatal and/or postnatal crack cocaine exposure in children between 4 and 6 years of age. Three groups were studied: Group 1, 18 prenatally-exposed children whose mothers continue to use crack; Group II, 28 children without prenatal exposure whose mothers presently use crack; and Group III, 28 children whose mothers never used crack. Mothers were street-recruited and were comparable in race and socioeconomic status. The three groups of children did not differ on neurological gross motor and expressive language measures. However, prenatally exposed children performed significantly worse than others on receptive language and visual motor drawing tests. Prenatal crack exposure predicted poor visual motor performance even after control for intrauterine alcohol and marijuana exposure, age, birth weight, and duration of maternal crack use.

History of in utero cocaine exposure in language-delayed children

To determine whether children with language delays are more likely to have been exposed to cocaine in utero than children with normal language development, a case-control study was undertaken. Based on routine office screening in our primary-care clinic over a 1-year period, we identified 29 consecutive children, aged 24 to 48 months, as language-delayed. They were compared with an approximate 2:1 match of children without language delay who had been seen in the clinic on the same days and who were of similar age. There was more reported cocaine use during pregnancy (six of 29, 21%) among the language-delayed children than among the controls (five of 71, 7%). This difference is statistically significant (P < 0.05, chi 2 = 3.92; odds ratio = 3.4 +/- 2.2). Discriminant analysis revealed that both cocaine and nicotine exposure were associated with delayed language development--with an unexpected negative, i.e., an antagonistic, protective, interactive effect (F[3,96] = 4.66, R2 = 12.7%, P < .005); neither gender nor caretaker contributed to language development in this sample. These results suggest that children with language delay detected in a clinical setting are more likely to have been exposed in utero to cocaine than children with normal language development. Prenatal cocaine exposure should be a risk factor in monitoring development in children.

Language and speech behaviors of children with undue lead absorption: a review of the literature

This article reviews the effects of chronic undue or low lead absorption on the speech and language behavior of children. While the effects of high-level lead poisoning have been documented, the effects of chronic low-lead absorption remain controversial. It is concluded that the evidence supports the presence of speech and language problems in some low-lead level children. The severity, duration, and specific nature of the problems, however, are not clear. Pertinent research issues are addressed.

Developmental language disability as a consequence of prenatal exposure to ethanol

Two pre-school-aged patients with a history of prenatal exposure to ethanol had abnormal head size and developmental delay. Both children were strikingly similar in physical appearance, behavior, and cognitive dysfunction. Facial features were typical of fetal alcohol syndrome. Head circumference greater than 97th percentile without hydrocephalus and no evidence of prenatal or postnatal growth failure were unusual for ethanol teratogenicity. Each child had a similar pattern of verbal and behavioral dysfunctions characterized by (1) marked hypervigilence, (2) distractability, and (3) cognitive confusion manifested as anxiety and behavioral disorganization. It is suggested that a history of prenatal exposure to ethanol associated with (1) large head circumference, (2) facial features of fetal alcohol syndrome, and (3) early developmental delay, particularly in language acquisition, and impaired modulation of attention and arousal may represent a possible new effect of alcohol teratogenicity.