Socioeconomic inequality in the prevalence of autism spectrum disorder: evidence from a U.S. cross-sectional study

Prevalence and incidence of autism spectrum disorder in an Israeli population

The prevalence of autism spectrum disorders has been steadily rising. In most parts of the world, rates as high as 1 % are reported, including in the United States. In Israel, previously reported prevalence rates have been in the 0.2 % range, and were based on parental reporting of diagnosis. In this study, records from one of the largest Israeli Health Maintenance organizations were used to calculate both incidence and prevalence of autism spectrum disorder (ASD) in Israel. Israeli prevalence of ASD was calculated at 0.48 % for 1-12 years olds and 0.65 % for 8 year old children in 2010, higher than previous Israeli reports, but still lower than prevalence estimates for the US. Incidence calculations ranged from 0.65 to 0.84 per 1,000 children for children 1-12 year olds. Reasons for these differences are suggested and discussed.

Are children born after assisted reproductive technology at increased risk of autism spectrum disorders? A systematic review

STUDY QUESTION

Are children born after assisted reproductive technology (ART) at increased risk of autism spectrum disorders (ASD)?

SUMMARY ANSWER

There is no evidence that ART significantly increases the risk of ASD in the offspring.

WHAT IS KNOWN ALREADY

A few systematic reviews have explored the correlation between assisted conception and ASD with inconclusive results, partly due to the heterogeneity of diagnostic criteria and methodology in the different studies.

STUDY DESIGN, SIZE, DURATION

Systematic review of 7 observational studies (2 cohort and 5 case-control) encompassing 9216 subjects diagnosed with ASD published since 2000.

MATERIALS, SETTING, METHODS

Literature searches were conducted to retrieve observational studies on the risk of ASD in ART population. Databases searched included PubMed, EMBASE and PsycINFO. In order to obtain more consistent results, we only included the studies in which (i) subjects with either infantile autism or ASD could be identified according to international classification systems and (ii) the diagnosis was obtained from hospital records. Seven studies matched the inclusion criteria.

MAIN RESULTS AND THE ROLE OF CHANCE

Four out of seven studies, including the two with the best quality scores, did not show an association between ART and ASD. The two papers supporting an increased risk of autism following ART had the lowest quality scores, due to major methodological limitations. Only one paper showed a protective role of ART.

LIMITATIONS, REASONS FOR CAUTION

In spite of the strict inclusion criteria applied as to the diagnosis of ASD, the papers selected are heterogeneous in many aspects including study design, definitions of ART, data source and analysed confounders.

WIDER IMPLICATIONS OF THE FINDINGS

At present, there is no evidence that ART is significantly associated with ASD and hence that current health policies should be modified. The divergent results of some of the studies suggest that further prospective, large and high-quality studies are still needed.

STUDY FUNDING/COMPETING INTEREST(S)

This work was supported, in part, by the Italian Ministry of Health and by Tuscany Region. The authors have no competing interests to declare.

TRIAL REGISTRATION NUMBER

N/A.

Autism in Glasgow: cumulative incidence and the effects of referral age, deprivation and geographical location

BACKGROUND

Referrals to the Greater Glasgow Community Autism Team (CAT) made before the child's sixth birthday were analysed to obtain an estimation of the proportion of children in Greater Glasgow with childhood autism and investigate whether there were any variations in diagnosis rates, or in age at referral and diagnosis, depending on deprivation or geographical location.

METHODS

An analysis was made of the database recording referrals to Greater Glasgow CAT, between 2004 and 2007 inclusive, of children referred by age 6 years, comprising 584 cases. Cumulative incidence was calculated for childhood autism. Ages at referral and diagnosis were also analysed.

RESULTS

For this subset of children, there were 246 diagnosed cases of childhood autism, a cumulative incidence from 2004 until 2007 of 11.1 per year per 10,000 children aged 0-6 years. Of children with an eventual diagnosis of autism by age 6, 72% were referred by the age of 4 years. Deprivation was found to have an association with referral and diagnostic rates, with higher rates seen in the most deprived. There was geographical variation in the cumulative incidence of autism.

CONCLUSION

Given that the populations were not known to differ in any manner that would lead to a true variation, the geographical variation in the cumulative incidence of autism in children up to 6 years in Greater Glasgow observed in this study is likely to represent differences in the care pathway between areas. Such differences may also explain the observed association with deprivation. Reasons for the variation are being explored.

Health utility assessment using EQ-5D among caregivers of children with autism

OBJECTIVES

Health utility of caregivers of children with autism was assessed by using the EuroQol five-dimensional (EQ-5D) questionnaire. Utility scores of autism caregivers were compared with norms for the general adult US population. Predictors of health utility were identified.

METHODS

A cross-sectional online survey design was used. Caregivers registered with the Interactive Autism Network were approached for participation in the online survey. Three hundred and sixteen usable responses were received. Health utility among caregivers was calculated and compared with the US population norms by using Student's t test. Problems in EQ-5D questionnaire domains and utility scores were analyzed by study characteristics by using Kruskal-Wallis analysis of variance. Factors predicting health utility were identified by using ordinary least square regression.

RESULTS

Roughly 94% of the caregivers who participated in the study were females. As compared to their counterparts in the general US population, caregivers who were aged 18 to 44 years and were females had lower utility scores (P < 0.001). Significant differences in utility scores were observed among caregivers. When compared to males, females had lower health utility. Caregivers of lower socioeconomic status had lower utility scores and reported more problems in EQ-5D questionnaire domains than did those from higher socioeconomic status. Caregiver burden was inversely correlated with health utility. Caregiver physical and mental health status, objective strain, education, and relationship with the care recipient were found to significantly predict health utility (adjusted R(2) ~57%).

CONCLUSIONS

Autism caregivers had lower health utility than did the general adult US population. There is an immediate need to address health concerns among this growing population.

The prevalence of neurodevelopmental disorders in children prenatally exposed to antiepileptic drugs

The aim of this study was to compare the prevalence of diagnosed neurodevelopmental disorders in children exposed, in utero, to different antiepileptic drug treatments. A prospective cohort of women with epilepsy and a control group of women without epilepsy were recruited from antenatal clinics. The children of this cohort were followed longitudinally until 6 years of age (n=415). Diagnosis of a neurodevelopmental disorder was made independently of the research team. Multiple logistic regression analysis revealed an increase in risk of neurodevelopmental disorders in children exposed to monotherapy sodium valproate (VPA) (6/50, 12.0%; aOR 6.05, 95%CI 1.65 to 24.53, p=0.007) and in those exposed to polytherapy with sodium VPA (3/20, 15.0%; aOR 9.97, 95% CI 1.82 to 49.40, p=0.005) compared with control children (4/214; 1.87%). Autistic spectrum disorder was the most frequent diagnosis. No significant increase was found among children exposed to carbamazepine (1/50) or lamotrigine (2/30). An accumulation of evidence demonstrates that the risks associated with prenatal sodium VPA exposure include an increased prevalence of neurodevelopmental disorders. Whether such disorders are discrete or represent the severe end of a continuum of altered neurodevelopmental functioning requires further investigation. Replication and extension of this research is required to investigate the mechanism(s) underpinning the relationship. Finally, the increased likelihood of neurodevelopmental disorders should be communicated to women for whom sodium VPA is a treatment option.

Translational animal models of autism and neurodevelopmental disorders

Autism is a neurodevelopmental disorder whose diagnosis is based on three behavioral criteria: unusual reciprocal social interactions, deficits in communication, and stereotyped repetitive behaviors with restricted interests. A large number of de novo single gene mutations and chromosomal deletions are associated with autism spectrum disorders. Based on the strong genetic evidence, mice with targeted mutations in homologous genes have been generated as translational research tools. Mouse models of autism have revealed behavioral and biological outcomes of mutations in risk genes. The field is now poised to employ the most robust phenotypes in the most replicable mouse models for preclinical screening of novel therapeutics.

Frequency and pattern of documented diagnostic features and the age of autism identification

OBJECTIVE

The DSM-IV-TR specifies 12 behavioral features that can occur in hundreds of possible combinations to meet diagnostic criteria for autism spectrum disorder (ASD). This paper describes the frequency and variability with which the 12 behavioral features are documented in a population-based cohort of 8-year-old children under surveillance for ASD, and examines whether documentation of certain features, alone or in combination with other features, is associated with earlier age of community identification of ASD.

METHOD

Statistical analysis of behavioral features documented for a population-based sample of 2,757 children, 8 years old, with ASD in 11 geographically-defined areas in the US participating in the Autism and Developmental Disabilities Monitoring Network in 2006.

RESULTS

The median age at ASD identification was inversely associated with the number of documented behavioral features, decreasing from 8.2 years for children with only seven behavioral features to 3.8 years for children with all 12. Documented impairments in nonverbal communication, pretend play, inflexible routines, and repetitive motor behaviors were associated with earlier identification, whereas impairments in peer relations, conversational ability, and idiosyncratic speech were associated with later identification.

CONCLUSIONS

The age dependence of some of the behavioral features leading to an autism diagnosis, as well as the inverse association between age at identification and number of behavioral features documented, have implications for efforts to improve early identification. Progress in achieving early identification and provision of services for children with autism may be limited for those with fewer ASD behavioral features, as well as features likely to be detected at later ages.

The Study to Explore Early Development (SEED): a multisite epidemiologic study of autism by the Centers for Autism and Developmental Disabilities Research and Epidemiology (CADDRE) network

The Study to Explore Early Development (SEED), a multisite investigation addressing knowledge gaps in autism phenotype and etiology, aims to: (1) characterize the autism behavioral phenotype and associated developmental, medical, and behavioral conditions and (2) investigate genetic and environmental risks with emphasis on immunologic, hormonal, gastrointestinal, and sociodemographic characteristics. SEED uses a case-control design with population-based ascertainment of children aged 2-5 years with an autism spectrum disorder (ASD) and children in two control groups-one from the general population and one with non-ASD developmental problems. Data from parent-completed questionnaires, interviews, clinical evaluations, biospecimen sampling, and medical record abstraction focus on the prenatal and early postnatal periods. SEED is a valuable resource for testing hypotheses regarding ASD characteristics and causes.

Ambient air pollution and autism in Los Angeles county, California

BACKGROUND

The prevalence of autistic disorder (AD), a serious developmental condition, has risen dramatically over the past two decades, but high-quality population-based research addressing etiology is limited.

OBJECTIVES

We studied the influence of exposures to traffic-related air pollution during pregnancy on the development of autism using data from air monitoring stations and a land use regression (LUR) model to estimate exposures.

METHODS

Children of mothers who gave birth in Los Angeles, California, who were diagnosed with a primary AD diagnosis at 3-5 years of age during 1998-2009 were identified through the California Department of Developmental Services and linked to 1995-2006 California birth certificates. For 7,603 children with autism and 10 controls per case matched by sex, birth year, and minimum gestational age, birth addresses were mapped and linked to the nearest air monitoring station and a LUR model. We used conditional logistic regression, adjusting for maternal and perinatal characteristics including indicators of SES.

RESULTS

Per interquartile range (IQR) increase, we estimated a 12-15% relative increase in odds of autism for ozone [odds ratio (OR) = 1.12, 95% CI: 1.06, 1.19; per 11.54-ppb increase] and particulate matter ≤ 2.5 µm (OR = 1.15; 95% CI: 1.06, 1.24; per 4.68-μg/m3 increase) when mutually adjusting for both pollutants. Furthermore, we estimated 3-9% relative increases in odds per IQR increase for LUR-based nitric oxide and nitrogen dioxide exposure estimates. LUR-based associations were strongest for children of mothers with less than a high school education.

CONCLUSION

Measured and estimated exposures from ambient pollutant monitors and LUR model suggest associations between autism and prenatal air pollution exposure, mostly related to traffic sources.

Differences in autism symptoms between minority and non-minority toddlers

Little is known about whether early symptom presentation differs in toddlers with ASD from ethnic minority versus non-minority backgrounds. Within a treatment study for toddlers with ASD, we compared 19 minority to 65 Caucasian children and their parents on variables obtained from the Mullen Scales of Early Learning, Autism Diagnostic Observation Schedule, and Communication and Symbolic Behavior Scales Caregiver Questionnaire. The majority of parents were from the upper classes irrespective of ethnic membership. Minority children had lower scores in language, communication, and gross motor than non-minority children. Findings indicate that subtle communication delays may be undetected or presumed unremarkable by parents of minority toddlers, and that more significant delays are needed to prompt the search for intervention services.

Developmental and autism screening through 2-1-1: reaching underserved families

BACKGROUND

Developmental disorders, including autism spectrum disorders (ASDs), are increasing in prevalence. Early identification is necessary for early intervention, which is critical for reducing challenges and lifetime costs, especially for ASDs. Because not all children have equal access to developmental and autism screening through primary care settings, nontraditional methods are needed to reach underserved populations.

PURPOSE

In this proof-of-concept study, the 2-1-1 Los Angeles County Developmental Screening Project (2-1-1 LA Project) provided developmental and autism screening by telephone in a population of low-income and racially and ethnically diverse children.

METHODS

Aggregate data were reviewed for 2845 children who were screened for developmental delays using the Parents' Evaluation of Developmental Status (PEDS) instrument and/or autism using the Modified Checklist for Autism in Toddlers (M-CHAT) instrument between September 1, 2009, and October 31, 2011.

RESULTS

Data analysis was conducted December 2011 through February 2012. A majority of children (56%) screened with the PEDS had a moderate to high risk of developmental delays, including 28.2% classified as high-risk, which indicates need for further evaluation. Among 1605 children screened with the M-CHAT, 21.2% had an elevated risk of ASDs. Follow-up care coordination was provided for 2625 children to facilitate completion of referrals for diagnostic evaluation, early childhood education, and other developmental or behavioral needs.

CONCLUSIONS

The project's approach enhanced access to screenings and referral uptake in a population of children that may have difficulty accessing primary care. Findings suggest the potential of nontraditional developmental screening models.

What the DSM-5 portends for research, diagnosis, and treatment of autism spectrum disorders

In May 2013 the APA will release DSM-5, which will restructure the diagnostic classification for autism spectrum disorders (ASDs) into a single category. The proposed changes in DSM-5 aim to better reflect the current state of research by consistently identifying the core features in social/communication and restrictive and repetitive behaviors that are specific to ASDs. This review describes the empirical and theoretical bases of research in the nosology of ASDs, given the impending shift in DSM-5 diagnostic criteria. General issues in diagnosis and prevalence are described, with differences between DSM-IV and DSM-5 highlighted. To address concerns about the application of the proposed DSM-5 criteria, the current literature assessing the sensitivity and specificity of the proposed DSM-5 criteria is reviewed. Last, we discuss the implications of the changes in DSM-5 for the treatment of ASDs and recommend areas for future research.

Increasing autism prevalence in metropolitan New Jersey

High baseline autism spectrum disorder prevalence estimates in New Jersey led to a follow-up surveillance. The objectives were to determine autism spectrum disorder prevalence in the year 2006 in New Jersey and to identify changes in the prevalence of autism spectrum disorder or in the characteristics of the children with autism spectrum disorder, between 2002 and 2006. The cohorts included 30,570 children, born in 1998 and 28,936 children, born in 1994, residing in Hudson, Union, and Ocean counties, New Jersey. Point prevalence estimates by sex, ethnicity, autism spectrum disorder subtype, and previous autism spectrum disorder diagnosis were determined. For 2006, a total of 533 children with autism spectrum disorder were identified, consistent with prevalence of 17.4 per 1000 (95% confidence interval = 15.9–18.9), indicating a significant increase in the autism spectrum disorder prevalence (p < 0.001), between 2002 (10.6 per 1000) and 2006. The rise in autism spectrum disorder was broad, affecting major demographic groups and subtypes. Boys with autism spectrum disorder outnumbered girls by nearly 5:1. Autism spectrum disorder prevalence was higher among White children than children of other ethnicities. Additional studies are needed to specify the influence of better awareness of autism spectrum disorder prevalence estimates and to identify possible autism spectrum disorder risk factors. More resources are necessary to address the needs of individuals affected by autism spectrum disorder.

Evaluating Changes in the Prevalence of the Autism Spectrum Disorders (ASDs)

Autism spectrum disorders (ASDs) are estimated to occur among about one percent of children in the United States. This estimate is in line with estimates from other industrialized countries. However, the identified prevalence of ASDs has increased significantly in a short time period based on data from multiple studies including the U.S. Centers for Disease Control and Prevention's (CDC) Autism and Developmental Disabilities Monitoring (ADDM) Network. Whether increases in ASD prevalence are partly attributable to a true increase in the risk of developing ASD or solely to changes in community awareness and identification patterns is not known. It is clear that more children are identified with an ASD now than in the past and the impact on individuals, families, and communities is significant. However, disentangling the many potential reasons for ASD prevalence increases has been challenging. Understanding the relative contribution of multiple factors such as variation in study methods, changes in diagnostic and community identification, and potential changes in risk factors is an important priority for the ADDM Network and for CDC. This article summarizes the discussion from a workshop that was co-sponsored by CDC and Autism Speaks as a forum for sharing knowledge and opinions of a diverse range of stakeholders about changes in ASD prevalence. Panelists discussed recommendations for building on existing infrastructure and developing new initiatives to better understand ASD trends. The information, research, and opinions shared during this workshop add to the knowledge base about ASD prevalence in an effort to stimulate further work to understand the multiple reasons behind increasing ASD prevalence.

The spatial distribution of known predictors of autism spectrum disorders impacts geographic variability in prevalence in central North Carolina

BACKGROUND

The causes of autism spectrum disorders (ASD) remain largely unknown and widely debated; however, evidence increasingly points to the importance of environmental exposures. A growing number of studies use geographic variability in ASD prevalence or exposure patterns to investigate the association between environmental factors and ASD. However, differences in the geographic distribution of established risk and predictive factors for ASD, such as maternal education or age, can interfere with investigations of ASD etiology. We evaluated geographic variability in the prevalence of ASD in central North Carolina and the impact of spatial confounding by known risk and predictive factors.

METHODS

Children meeting a standardized case definition for ASD at 8 years of age were identified through records-based surveillance for 8 counties biennially from 2002 to 2008 (n=532). Vital records were used to identify the underlying cohort (15% random sample of children born in the same years as children with an ASD, n=11,034), and to obtain birth addresses. We used generalized additive models (GAMs) to estimate the prevalence of ASD across the region by smoothing latitude and longitude. GAMs, unlike methods used in previous spatial analyses of ASD, allow for extensive adjustment of individual-level risk factors (e.g. maternal age and education) when evaluating spatial variability of disease prevalence.

RESULTS

Unadjusted maps revealed geographic variation in surveillance-recognized ASD. Children born in certain regions of the study area were up to 1.27 times as likely to be recognized as having ASD compared to children born in the study area as a whole (prevalence ratio (PR) range across the study area 0.57-1.27; global P=0.003). However, geographic gradients of ASD prevalence were attenuated after adjusting for spatial confounders (adjusted PR range 0.72-1.12 across the study area; global P=0.052).

CONCLUSIONS

In these data, spatial variation of ASD in central NC can be explained largely by factors impacting diagnosis, such as maternal education, emphasizing the importance of adjusting for differences in the geographic distribution of known individual-level predictors in spatial analyses of ASD. These results underscore the critical importance of accounting for such factors in studies of environmental exposures that vary across regions.

An ecological study on childhood autism

BACKGROUND AND METHODS

Idiopathic autism, suspected to be caused by exposure of genetically susceptible individuals to unknown environmental triggers, has increased dramatically in the past 25 years. The objectives of our study were to determine, using a linear regression model, whether the county prevalence of autism in the Pacific Northwest of the United States was associated with the source of drinking water for that county and whether this relationship was dependent on the level of environmental pollutants and meteorological factors in the county.

RESULTS

We found the previously reported relationship between precipitation and autism in a county was dependent on the amount of drinking water derived from surface sources in the county. We also found a positive association between the EPA's risk of neurological disease and autism, but this relationship was only present in warm areas.

CONCLUSIONS

Our study provides evidence for the hypothesis that environmental factors are associated with autism and that meteorological factors play a role in this relationship.

Concerns and considerations among caregivers of a child with autism in Qatar

BACKGROUND

Autism impacts the lives of the family looking after a child with the condition in different ways, and forces family members to modify their daily lives to suit their reality. To our knowledge, no previous research investigated concern and considerations of parents/caregivers of children with autism in Qatar or the Arabic speaking Middle Eastern region.

METHODS

Caregivers of a child who was between the age of 3 to 17 years old at the time of the study and who was diagnosed with ASD (Autistic Group or AG) were recruited from the two main developmental pediatric and children rehabilitation clinics in Qatar. The control group (non-autism group, or NAG) was represented by caregivers of a non-autistic child between the age of 3 to 17 years old at the time of the study and who were visiting a family clinic of a primary health care facility for routine medical check-up. Data collected from both groups included related to the child (e.g. the child's date of birth, his/her relation to the caregiver, number of siblings, number of hours of sleep in a day, number of hours spent watching television or videos prior to age 3, time spent indoors prior to age 3, absenteeism from school, and use of a nanny to care for the child) and to the caregiver (education level, profession, level of consanguinity using the phylogram method). In addition to these questions, caregivers in the AG were asked specific questions around maternal concern and considerations in respect to the future of their children and the specialized services they receive.

RESULTS

Children in the autism group spent more time indoors, watching television, or sleeping than children in the non-autism group. Only around 40% of caregivers in the autism group said they would encourage their child to get married and become a parent when s/he grows up. A number of caregivers of children with autism frequently utilize specialized rehabilitation services; others did express their needs for these services and made comments about having to wait a long time before they were provided with some of the services. Religious faith helped caregivers in accepting having a child with autism. General health-related quality of life did not differ significantly between the caregivers of the two groups, although mental health was consistently poorer in the autism group of caregivers.

CONCLUSIONS

The study draws attention to the concerns of the families of children with autism and their expectations about the future of their children. The findings can be used by policy makers in planning services to support these families in Qatar.

Perinatal stress, brain inflammation and risk of autism-review and proposal

BACKGROUND

Autism Spectrum Disorders (ASD) are neurodevelopmental disorders characterized by varying deficits in social interactions, communication, and learning, as well as stereotypic behaviors. Despite the significant increase in ASD, there are few if any clues for its pathogenesis, hampering early detection or treatment. Premature babies are also more vulnerable to infections and inflammation leading to neurodevelopmental problems and higher risk of developing ASD. Many autism "susceptibility" genes have been identified, but "environmental" factors appear to play a significant role. Increasing evidence suggests that there are different ASD endophenotypes.

DISCUSSION

We review relevant literature suggesting in utero inflammation can lead to preterm labor, while insufficient development of the gut-blood-brain barriers could permit exposure to potential neurotoxins. This risk apparently may increase in parents with "allergic" or autoimmune problems during gestation, or if they had been exposed to stressors. The presence of circulating auto-antibodies against fetal brain proteins in mothers is associated with higher risk of autism and suggests disruption of the blood-brain-barrier (BBB). A number of papers have reported increased brain expression or cerebrospinal fluid (CSF) levels of pro-inflammatory cytokines, especially TNF, which is preformed in mast cells. Recent evidence also indicates increased serum levels of the pro-inflammatory mast cell trigger neurotensin (NT), and of extracellular mitochondrial DNA (mtDNA), which is immunogenic. Gene mutations of phosphatase and tensin homolog (PTEN), the negative regulator of the mammalian target of rapamycin (mTOR), have been linked to higher risk of autism, but also to increased proliferation and function of mast cells.

SUMMARY

Premature birth and susceptibility genes may make infants more vulnerable to allergic, environmental, infectious, or stress-related triggers that could stimulate mast cell release of pro-inflammatory and neurotoxic molecules, thus contributing to brain inflammation and ASD pathogenesis, at least in an endophenotype of ASD patients.

Maternal smoking during pregnancy and the prevalence of autism spectrum disorders, using data from the autism and developmental disabilities monitoring network

BACKGROUND

Reported associations between gestational tobacco exposure and autism spectrum disorders (ASDs) have been inconsistent.

OBJECTIVE

We estimated the association between maternal smoking during pregnancy and ASDs among children 8 years of age.

METHODS

This population-based case-cohort study included 633,989 children, identified using publicly available birth certificate data, born in 1992, 1994, 1996, and 1998 from parts of 11 U.S. states subsequently under ASD surveillance. Of these children, 3,315 were identified as having an ASD by the active, records-based surveillance of the Autism and Developmental Disabilities Monitoring Network. We estimated prevalence ratios (PRs) of maternal smoking from birth certificate report and ASDs using logistic regression, adjusting for maternal education, race/ethnicity, marital status, and maternal age; separately examining higher- and lower-functioning case subgroups; and correcting for assumed under-ascertainment of autism by level of maternal education.

RESULTS

About 13% of the source population and 11% of children with an ASD had a report of maternal smoking in pregnancy: adjusted PR (95% confidence interval) of 0.90 (0.80, 1.01). The association for the case subgroup autistic disorder (1,310 cases) was similar: 0.88 (0.72, 1.08), whereas that for ASD not otherwise specified (ASD-NOS) (375 cases) was positive, albeit including the null: 1.26 (0.91, 1.75). Unadjusted associations corrected for assumed under-ascertainment were 1.06 (0.98, 1.14) for all ASDs, 1.12 (0.97, 1.30) for autistic disorder, and 1.63 (1.30, 2.04) for ASD-NOS.

CONCLUSIONS

After accounting for the potential of under-ascertainment bias, we found a null association between maternal smoking in pregnancy and ASDs, generally. The possibility of an association with a higher-functioning ASD subgroup was suggested, and warrants further study.

Hospitalization burden among individuals with autism

The objective of this study was to assess the inpatient care burden among individuals with autism using the 2007 Health Care Utilization Project Nationwide Inpatient Sample [HCUP-NIS]). There were ~26,000 hospitalizations among individuals with autism in 2007, with an overall rate of 65.6/100,000 admissions. Rates of hospitalizations were the highest among individuals with autism aged 10-20 years, males, having household income >$63,000, and with private insurance, respectively. In terms of hospital characteristics, rates were the highest in hospitals in large urban areas, located in the Northeast region, and with teaching status, respectively. Individuals with autism had significantly higher LOS (6.5 vs. 4.2; p < 0.0001) and total charges ($24,862 vs. $23,225; p < 0.0001) as compared to those without autism.

Parental socioeconomic status and risk of offspring autism spectrum disorders in a Swedish population-based study

OBJECTIVE

Epidemiological studies in the United States consistently find autism spectrum disorders (ASD) to be overrepresented in high socioeconomic status (SES) families. These findings starkly contrast with SES gradients of many health conditions, and may result from SES inequalities in access to services. We hypothesized that prenatal measures of low, not high, parental SES would be associated with an increased risk of offspring ASD, once biases in case ascertainment are minimized.

METHOD

We tested this hypothesis in a population-based study in Sweden, a country that has free universal healthcare, routine screening for developmental problems, and thorough protocols for diagnoses of ASD. In a case-control study nested in a total population cohort of children aged 0 to 17 years living in Stockholm County between 2001 and 2007 (N = 589,114), we matched ASD cases (n = 4,709) by age and sex to 10 randomly selected controls. We retrieved parental SES measures collected at time of birth by record linkage.

RESULTS

Children of families with lower income, and of parents with manual occupations (OR = 1.4, 95% CI = 1.3-1.6) were at higher risk of ASD. No important relationships with parental education were observed. These associations were present after accounting for parental ages, migration status, parity, psychiatric service use, maternal smoking during pregnancy, and birth characteristics; and regardless of comorbid intellectual disability.

CONCLUSIONS

Lower, not higher, socioeconomic status was associated with an increased risk of ASD. Studies finding the opposite may be underestimating the burden of ASD in lower SES groups.

Autistische Störungen – State-of-the-Art und neuere Entwicklungen

Der vorliegende Überblicksartikel baut auf dem «State-of-the-Art»-Vortrag zu tiefgreifenden Entwicklungsstörungen bei der 32. Jahrestagung der Deutschen Gesellschaft für Kinder- und Jugendpsychiatrie, Psychosomatik und Psychotherapie (DGKJP) im März 2011 in Essen auf und fasst die neuesten Erkenntnisse bezüglich epidemiologischer Studien (Komorbidität, Risikofaktoren), Frühdiagnose, Klassifikation und evidenzbasierter Therapieverfahren im Bereich medikamentöser Therapie sowie Autismus-spezifischer Frühförderung und Verhaltenstherapie zusammen. In allen diesen Bereichen hat die Forschung in den letzten Jahren zu einem besseren Verständnis und zu einer effektiveren Therapie von Autism Spectrum Disorders beigetragen.

Prevalence of autism spectrum disorders in Hispanic and non-Hispanic white children

OBJECTIVE

The number of individuals diagnosed with autism spectrum disorders (ASDs) continues to increase in the United States and other developed countries; however, ASD is diagnosed less commonly in Hispanic than in non-Hispanic white individuals. This report analyzes differences in ASD prevalence between Hispanic and non-Hispanic whites in a large, population-based sample of 8-year-old children, and explores how prevalence has changed over time.

METHODS

Population-based surveillance of ASD was conducted on 142 717 8-year-old children. Evaluation of clinical and educational records resulted in 1212 children meeting the case definition criteria in 4 study years between 2000 and 2006.

RESULTS

ASD prevalence in Hispanic children was lower than in non-Hispanic white children (P < .005) for all study years. More Hispanic than non-Hispanic white children met the case definition for intellectual disability (P < .05) in study years 2004 and 2006. Prevalence of ASD diagnosis increased in both groups; the Hispanic prevalence almost tripled, from 2.7 per 1000 in 2000 to 7.9 per 1000 in 2006. A comparison of prevalence ratios found that Hispanic and non-Hispanic white ASD prevalence became significantly more similar from 2000 to 2006 (χ(2) = 124.89, P < .001).

CONCLUSIONS

The ASD prevalence for Hispanic individuals in this population-based sample is substantially higher than previously reported. Nonetheless, Hispanic children continue to have a significantly lower ASD prevalence in comparison with non-Hispanic whites. The prevalence of ASD is increasing in both populations, and results indicate that the gap in prevalence between groups is decreasing.

Ageing in people with autistic spectrum disorder

BACKGROUND

Although autism in children and in adults attracts attention with respect to clinical and research needs, autism in the older individuals has not been considered to any degree. We review the evidence for urgently addressing the question of ageing in people with autistic spectrum disorder (ASD), focusing on those with disability.

METHODS

Perspectives are reviewed in relation to demographics, experiences of relatives or carers, anticipated residential care needs, requirement for specifically designed cognitive assessment tools and importance of initiating new brain ageing research initiatives in this area.

RESULTS

With escalating numbers of ASD individuals with disability reaching old age, provision of care is the paramount issue that is only beginning to be addressed in a few European communities and in the USA. How ageing affects cognition in such individuals as they reach an age no longer consistent with parental care is unknown, lacking any published evidence, and there is a clear need to design cognitive and behavioural assessment tools appropriate to ageing in ASD individuals with disability, as was the case with respect to dementia as a whole. Although there is a growing body of evidence on pathological, imaging, neuropharmacological and other key brain abnormalities in ASD, these are, to date, confined to children and young (only rarely to middle aged) adults.

CONCLUSIONS

The need for new initiatives in research into ageing in ASD is urgent. Apart from a growing care crisis, the prospect of understanding brain ageing in this population may bring potential rewards beyond immediate clinical need given the precedent of Down syndrome.

Participation in social activities among adolescents with an autism spectrum disorder

Background

Little is known about patterns of participation in social activities among adolescents with an autism spectrum disorder (ASD). The objectives were to report nationally representative (U.S.) estimates of participation in social activities among adolescents with an ASD, to compare these estimates to other groups of adolescents with disabilities, and examine correlates of limited social participation.

Methods and Findings

We analyzed data from wave 1 of the National Longitudinal Transition Study 2, a large cohort study of adolescents enrolled in special education. Three comparison groups included adolescents with learning disabilities, mental retardation, and speech/language impairments. Adolescents with an ASD were significantly more likely never to see friends out of school (43.3%), never to get called by friends (54.4%), and never to be invited to social activities (50.4%) when compared with adolescents from all the other groups. Correlates of limited social participation included low family income and having impairments in conversational ability, social communication, and functional cognitive skills.

Conclusions

Compared with prior research, our study significantly expands inquiry in this area by broadening the range of social participation indicators examined, increasing the external validity of findings, focusing on the under-studied developmental stage of adolescence, and taking an ecological approach that included many potential correlates of social participation. There were notable differences in social participation by income, a dimension of social context seldom examined in research on ASDs.

Association between parental nativity and autism spectrum disorder among US-born non-Hispanic white and Hispanic children, 2007 National Survey of Children's Health

BACKGROUND

Limited studies suggest the prevalence of autism spectrum disorders (ASD) varies by whether maternal and child birth country are discordant.

OBJECTIVE/HYPOTHESIS

We explored associations between ASD and maternal and paternal nativity in a sample of US-born non-Hispanic white (NHW, n = 37,265) and US-born Hispanic (n = 4,690) children in the 2007 National Survey of Children's Health (NSCH).

METHODS

We assessed ASD prevalence within race-ethnicity and parental nativity subgroups. Prevalence ratios (aPR), comparing each group to NHW children with 2 US-born parents, were adjusted for child age, sex, and receipt of care in a medical home. Estimates were weighted to reflect US noninstitutionalized children. Standard errors were adjusted to account for the complex sample design.

RESULTS

In NHW children with 2 US-born parents, ASD prevalence was 1.19%; estimates were similar for NHW children with a foreign-born mother or father. There was a striking heterogeneity between Hispanic children with 2 US-born versus 2 foreign-born parents (ASD prevalence 2.39% versus 0.31%, p = .05). Even after adjustment, PRs comparing ASD prevalence in Hispanic versus NHW children were vastly different for Hispanic subgroups, suggesting a substantially lower prevalence for Hispanic children with both parents foreign-born (aPR 0.2, 95% confidence interval 0.1-0.5) and a higher prevalence for Hispanic children with both parents US-born (aPR 2.0 [0.8-4.6]).

CONCLUSIONS

Previous studies comparing ASD prevalence between NHW and Hispanic children based on a composite Hispanic grouping without consideration of parental nativity likely missed important differences between these racial-ethnic groups. Continuing efforts toward improving early identification in Hispanic children are needed.

The association of autism diagnosis with socioeconomic status

Background: In 2007 the Centers for Disease Control and Prevention (CDC) reported a higher prevalence of autism spectrum disorder (ASD) in New Jersey, one of the wealthiest states in the United States, than in other surveillance regions.

Objective: To examine the association of socioeconomic status (SES) with ASD prevalence.

Methods: Information on eight-year-olds with ASD from four counties was abstracted from school and medical records. US Census 2000 provided population and median household income data.

Results: 586 children with ASD were identified: autism prevalence was 10.2/1000, higher in boys than girls (16 vs. 4/1000); higher in white and Asian non-Hispanics than in black non-Hispanics and Hispanics (12.5, 14.0, 9.0, and 8.5/1000, respectively); and higher (17.2/1000 (95% CI 14.0–21.1)) in tracts with median income >US$90,000 than in tracts with median income ≤US$30,000 (7.1 (95% CI 5.7–8.9)). Number of professional evaluations was higher, and age at diagnosis younger, in higher income tracts ( p < .001), but both measures spanned a wide overlapping range in all SES levels. In multivariable models race/ethnicity did not predict ASD, but the prevalence ratio was 2.2 (95% CI 1.5–3.1) when comparing highest with lowest income tracts.

Conclusions: In the US state of New Jersey, ASD prevalence is higher in wealthier census tracts, perhaps due to differential access to pediatric and developmental services.

Autism spectrum disorders: toward a gendered embodiment model

One of the most consistent observations in the epidemiology of autism spectrum disorders (ASD) is the preponderance of male cases. A few hypotheses have been put forth which attempt to explain this divergence in terms of sex-linked biology, with limited success. Feminist epidemiologists suggest the importance of investigating specific mechanisms for male-female differences in health outcomes, which may include sex-linked biology and/or gender relations, as well as complex biosocial interactions. Neither domain has been systematically investigated for autism, and the possible role of gender has been particularly neglected. In this article, we posit hypotheses about how social processes based on perception of persons as male or female, particularly patterns of social and physical interaction in early development, may affect the observed occurrence and diagnosis of ASD. We gesture toward an embodiment model, incorporating hypotheses about initial biological vulnerabilities to autism--which may or may not be differentially distributed in relation to sex biology--and their interactions with gender relations, which are demonstrably different for male and female infants. Toward building such a model, we first review the epidemiology of ASD with an eye toward male-female differences, then present a theory of gender as a "pervasive developmental environment" with relevance for the excess burden of autism among males. Finally, we suggest research strategies to further investigate this issue.

Socioeconomic Status and the Increased Prevalence of Autism in California

The prevalence of autism has increased precipitously-roughly 10-fold in the past 40 years-yet no one knows exactly what caused this dramatic rise. Using a large and representative dataset that spans the California birth cohorts from 1992 through 2000, we examine individual and community resources associated with the likelihood of an autism diagnosis over time. This allows us to identify key social factors that have contributed to increased autism prevalence. While individual-level factors, such as birth weight and parental education, have had a fairly constant effect on likelihood of diagnosis over time, we find that community-level resources drive increased prevalence. This study suggests that neighborhoods dynamically interact with the people living in them in different ways at different times to shape health outcomes. By treating neighborhoods as dynamic, we can better understand the changing socioeconomic gradient of autism and the increase in prevalence.

Autism and intellectual disability are differentially related to sociodemographic background at birth

BACKGROUND

Research findings investigating the sociodemographics of autism spectrum disorder (ASD) have been inconsistent and rarely considered the presence of intellectual disability (ID).

METHODS

We used population data on Western Australian singletons born from 1984 to 1999 (n = 398,353) to examine the sociodemographic characteristics of children diagnosed with ASD with or without ID, or ID without ASD compared with non-affected children.

RESULTS

The profiles for the four categories examined, mild-moderate ID, severe ID, ASD without ID and ASD with ID varied considerably and we often identified a gradient effect where the risk factors for mild-moderate ID and ASD without ID were at opposite extremes while those for ASD with ID were intermediary. This was demonstrated clearly with increased odds of ASD without ID amongst older mothers aged 35 years and over (odds ratio (OR) = 1.69 [CI: 1.18, 2.43]), first born infants (OR = 2.78; [CI: 1.67, 4.54]), male infants (OR = 6.57 [CI: 4.87, 8.87]) and increasing socioeconomic advantage. In contrast, mild-moderate ID was associated with younger mothers aged less than 20 years (OR = 1.88 [CI: 1.57, 2.25]), paternal age greater than 40 years (OR = 1.59 [CI: 1.36, 1.86]), Australian-born and Aboriginal mothers (OR = 1.60 [CI: 1.41, 1.82]), increasing birth order and increasing social disadvantage (OR = 2.56 [CI: 2.27, 2.97]). Mothers of infants residing in regional or remote areas had consistently lower risk of ASD or ID and may be linked to reduced access to services or under-ascertainment rather than a protective effect of location.

CONCLUSIONS

The different risk profiles observed between groups may be related to aetiological differences or ascertainment factors or both. Untangling these pathways is challenging but an urgent public health priority in view of the supposed autism epidemic.