The Prevalence of Autism in the World: An Umbrella Review and Meta-Analysis

Background A general perception is that ASD occurs equitably across demographic groups and there is no biological basis for a difference in prevalence between different ethnicities. A delayed pattern of diagnosis may be present in BME populations, but little information is available about variations in prevalence by ethnicity. Factors that seem to influence ethnic variability across studies include the case ascertainment approach, immigration status and access to care. A literature review examined the prevalence of childhood Autism Spectrum Disorder (ASD) in Black and Minority Ethnic (BME) populations. Our hypothesis was that the prevalence of childhood ASD in BME populations would be decreased compared to their White counterparts. Methods A computer-assisted search identified articles about the prevalence of childhood ASD in ethnic minorities. 7 search terms for ASD were linked with ‘OR’. Ethnicity search terms linked with ‘OR’ were: Ethnic group*, Minority group*, Black and ethnic minorit*, BME. The above two were linked with ‘prevalence’ by ‘AND’. Results We found 8 studies. ASD was assessed using DSM IV criteria. Methods of ascertaining ethnic groupings varied: in the US authors compared White vs Black, Hispanic and Asian ethnicity. In Israel, authors compared Jewish vs Arab and in the Netherlands, white Dutch vs minority European (English/French) vs non-European (Turkish/Moroccan). All studies showed a decreased prevalence of childhood ASD in ethnic minority populations. Possible reasons for this disparity included a cultural understanding of neurodevelopmental disorders, primary language spoken at home, maternal education, the severity of ASD and professional bias. Conclusions The prevalence of childhood ASD in BME populations is lower compared to their White counterparts. It is influenced by cultural values, with the diagnosis not being recognised in minority groups. This influences the wellbeing of children with ASD from already disadvantaged BME populations. Therefore, there is a need to provide education and better care

See related article on page 672 The prevalence and sociodemographic characteristics of children with autism spectrum disorders (ASD) remain an important public concern. Although reports of the prevalence of ASD vary widely,1 it is generally accepted that the prevalence is higher today than in the past and there have been recent reports of prevalence estimates as high as 2.7% of children.2 In countries where special education services are available, determining the prevalence of developmental disabilities, including ASD, from multiple sources is enhanced by the ability to identify children from education records. Prevalence estimates using this methodology have yielded estimates that are similar across sites and are higher when education records are included in addition to health records.3 Williams et al. describe the prevalence and characteristics of 11-year-old children with ASD in the UK in 2003 using a large representative sample of children who have been followed since birth in the Avon Longitudinal Study of Parents and Children (ALSPAC).4 ALSPAC offers a unique advantage: the ability to examine both health and education records in order to identify children with ASD. In the study, ICD-10 coded diagnoses for ASD were used to identify children with a developmental delay; a study diagnosis of ASD was then based on findings from a multidisciplinary assessment, as reviewed by an experienced clinician. A second independent source of cases for the study was from the PLASC (education) dataset, which included records of children in special schools; ASD as a primary or secondary concern was used to identify cases for the study. Almost all of the children in the study (94%) were found to have a statement of special educational needs, but because of privacy concerns, there was no way to link the health and education records in order to get a composite record for each child. But, no matter how complete the ascertainment of cases appears to be from multiple sources, some children might be missed because of under ascertainment of children with milder disabilities. Yet, in this study, the small percentage of children with childhood autism who had intellectual disability (mental retardation; 14.7%) or epilepsy (10.3%), suggests that more severely affected children may have been under ascertained. From ALSPAC, the overall prevalence of children receiving special education services for autism was 61.9 per 10 000 children, about 10 per 10 000 higher than the prevalence obtained from health sources using the ICD-10 diagnostic code for ASD, and consistent with results from other recent population studies.3 It has been documented that casting a wider net, e.g. applying behavioral criteria consistent with ASD from the records of children with other relevant clinical diagnoses, as well as those receiving special education services other than for ‘autism’, will yield more children who meet surveillance criteria for ASD. Data from a large multisite surveillance program in the US found that the prevalence of ASD among children who were ‘previously classified’ (i.e. had a diagnosis of ASD and/or received special education services for ‘autism’) was approximately 1.1 to 3.2 per 1000 children lower compared with the prevalence of ASD casting the wider net.3 The median age of diagnosis was available only from health records, and was 44.9 months (range 37–88mo), comparable to that of 8-year-old children (range 49–66mo) in the US.3 The male: female ratio of 6.8:1 with a trend toward females being more severely affected and the sociodemographic findings related to ethnicity, maternal education, and maternal age were not new findings. However, specific sociodemographic risk factors for ASD have been found to differ according to whether identification of the children with ASD was from education records or from health records. Overall, the findings from this study tell us once again that ASD is a common disorder of childhood and confirms that including education records as part of a multiple source ascertainment strategy yields a higher prevalence of ASD than if only health records are used. The results from ALSPAC indicate that, at a minimum, approximately 60 per 10 000 children in the UK have ASD and, based on several potential sources of under ascertainment of cases, the true prevalence of ASD in this community is likely to be even higher.

Autism spectrum disorder (ASD) is a complex neurodevelopmental disorder. Previous surveys have reported a steady increase in ASD prevalence in US children over the past decades. Several behavioral therapies and medications have been developed to treat the symptoms of ASD; however, little is known about the current status of treatment usage for children diagnosed as having ASD. To estimate the prevalence and treatment patterns of ASD among US children using nationally representative data. This study used data from the 2016 National Survey of Children's Health, a nationwide, population-based, cross-sectional survey. We included 43 032 children aged 3 to 17 years. Data were collected through questionnaires completed by a parent or guardian. Data were analyzed from February 2018 to March 2018. Outcome variables included ASD diagnosed by a physician or health professional and the use of behavioral treatment or medication treatment among children with ASD. Of the 43 032 included participants, 22 072 (51.3%) were male, and the mean (SD) age was 10.7 (4.4) years. The weighted prevalence of ever-diagnosed ASD and current ASD were 2.79% (95% CI, 2.46-3.12) and 2.50% (95% CI, 2.21-2.79), respectively. The state-level prevalence of ever-diagnosed ASD varied from 1.54% (95% CI, 0.60-2.48) in Texas to 4.88% (95% CI, 2.72-7.05) in Florida. Nationally, about 70% of children with current ASD (70.5%; 95% CI, 65.1-75.8) were treated; 43.3% (95% CI, 37.4-49.2) received behavioral treatment only, 6.9% (95% CI, 3.7-10.1) received medication treatment only, and 20.3% (95% CI, 16.5-24.1) received both behavioral and medication treatments. The remaining 29.5% (95% CI, 24.2-34.9) of children with current ASD did not receive either behavioral or medication treatment. This study showed that the prevalence of ASD in the United States was relatively high, and it varied substantially across US states. Almost 30% of US children with ASD did not receive behavioral or medication treatment, which calls for a critical need to understand and address the barriers for those children to receive appropriate treatments.

Estimates of the prevalence of intellectual disability or autism spectrum disorder (ASD) may vary depending on the methodology, geographical location, and sources of ascertainment. The National Disability Insurance Scheme (NDIS) in Australia was introduced progressively from 2016 to provide individualized funding for eligible people with a significant and permanent disability. Its recent inclusion as a source of ascertainment in the population-based Intellectual Disability Exploring Answers (IDEA) database in Western Australia has allowed comparisons of the prevalence of intellectual disability and ASD before and after its introduction. Prevalence of intellectual disability in 2020 was 22.5 per 1,000 (/1,000) live births compared with previous estimates in 2010 of 17/1,000, and for ASD, the estimate was 20.7/1,000 in 2020 compared with 5.1 /1,000 in 2010. Whilst the prevalence of ASD in Aboriginal individuals was about two-thirds that of non-Aboriginals, there was an increased prevalence of ASD in Aboriginal children under 10 years compared with non-Aboriginal children. The concurrent relaxation of ASD diagnostic practice standards in Western Australia associated with the administration of access to the NDIS and the release of the National Guidelines empowering single diagnosticians to determine the appropriateness of engaging additional diagnosticians to form a multidisciplinary team on ASD diagnosis, appear to be important factors associated with the increase in ASD diagnoses both with and without intellectual disability.

Autism spectrum disorder (ASD) prevalence estimates have varied by region. In this study, ASD prevalence, based on active case finding from multiple sources, was determined at the county and school district levels in the New Jersey metropolitan area. Among children born in 2008, residing in a four-county area and enrolled in public school in 2016, ASD prevalence was estimated to be 36 per 1000, but was significantly higher in one region-54 per 1000 and greater than 70 per 1000, in multiple school districts. Significant variation in ASD prevalence by race/ethnicity, socioeconomic status (SES), and school district size was identified. Highest prevalence was in mid-SES communities, contrary to expectation. Prevalence among Hispanic children was lower than expected, indicating a disparity in identification. Comprehensive surveillance should provide estimates at the county and town levels to appreciate ASD trends, identify disparities in detection or treatment, and explore factors influencing change in prevalence. LAY SUMMARY: We found autism prevalence to be 3.6% in New Jersey overall, but higher in one region (5.4%) and in multiple areas approaching 7.0%. We identified significant variation in autism spectrum disorder (ASD) prevalence by race/ethnicity, socioeconomic status (SES) and school district size. Mapping prevalence in smaller, well-specified, regions may be useful to better understand the true scope of ASD, disparities in ASD detection and the factors impacting ASD prevalence estimation.

Autism spectrum disorder (ASD) prevalence has increased markedly across high-income countries, including Norway, yet environmental drivers remain poorly understood. We hypothesized that historical lead exposure may inversely associate with ASD risk and potentially suppress the effects of vehicle emissions associated with urbanicity. We conducted a county-level ecological study using ASD prevalence data from the Norwegian Patient Register for children aged 6-12 years (born 1999-2005). Mean dental lead concentrations, measured in deciduous teeth collected between 1990 and 1994 (n = 2,746), served as a proxy for early-life lead exposure. Population density in 2002 was used as a proxy for vehicle emissions associated with urbanicity. ADHD and cerebral palsy (CP) were included as negative controls. Associations with log-transformed ASD prevalence were assessed using multivariable linear regression. Sensitivity analyses examined a later birth cohort and excluded an outlier county. Dental lead levels were inversely associated with ASD prevalence (p < 0.01), while population density was not significantly associated until adjusted for lead exposure (p = 0.08 and p < 0.05 with outlier excluded), consistent with a suppressor effect or negative confounding. No associations were observed for ADHD or CP. In sensitivity analyses, lead remained inversely associated with ASD only in multivariable models, while population density became a significant predictor. Higher historical lead exposure was associated with lower ASD prevalence in Norway. Declining lead exposure may have unmasked the neurodevelopmental effects of vehicle emissions. These findings support further investigation into metal interactions and highlight the complexity of environmental influences on ASD risk.

There are conflicting prevalence estimates of autism spectrum disorders (ASDs) in mainland China (China thereafter). This study is a comprehensive meta-analysis of the pooled prevalence of ASDs in the general population in China. Study investigators independently conducted a systematic literature search of the following databases: PubMed, EMBASE, PsycINFO, China National Knowledge Infrastructure, Chinese biomedical literature service system, and Wan Fang. Studies reporting prevalence of ASDs and autism in Chinese population were identified and analysed using the Comprehensive Meta-Analysis program with the random effects model. Forty-four studies were included in the meta-analysis comprising 2,337,321 subjects of whom 46.66 % were females. The mean age of subjects ranged from 1.6 to 8 years. Based on diagnostic criteria the pooled prevalence of ASDs was 39.23 per 10,000 (95% CI: 28.44-50.03 per 10,000, I2=89.2%); specifically, the prevalence of autism was 10.18 per 10,000 (95% CI: 8.46-11.89 per 10,000, I2=92.5%). Subgroup analyses revealed significant difference in the prevalence of ASDs between genders (72.77 per 10,000 in males vs. 16.45 per 10,000 in females). In conclusion, the prevalence of ASDs and autism in China was found generally lower than those reported in other countries. Further studies are needed to clarify the variation in prevalence.

The prevalence of autism spectrum disorder (ASD) among children and adolescents seem to be high in countries around the world, and it's worth understanding the latest prevalence and trends of ASD in children and adolescents. The purpose of this study was to examine the latest prevalence and decade trend of ASD among individuals aged 3-17years in the United States. A total of 13,198 individuals aged 3-17years were included. Annual data were examined from the National Health Interview Survey (2021-2022). Weighted prevalence for each of the selected developmental disabilities were calculated. This cross-sectional study estimated the weighted prevalence of autism spectrum disorder were 3.05, 3.79, and 3.42% among individuals aged 3-17years in the US in 2021, 2022, and the 2-year overall, respectively. We also observed a decade-long upward trend even after adjusting for demographic characteristics (P for trend < .05). The results of this study showed that the prevalence of ASD among children and adolescents aged 3-17years in the United States remained high and has increased over the past decade. The further investigation is necessary to evaluate potential modifiable risk factors and causes of ASD.

Purpose: Regularly analyzing the prevalence of autism spectrum disorder (ASD) is im-portant to inform policies and strategies for proper management. The present study aimed to estimate trends in ASD prevalence according to age and time in Korean chil-dren.Methods: We monitored the annual prevalence of ASD in children aged 2 to 18 years based on information from Statistics Korea and the Korean National Health Insurance Service. We estimated changes in prevalence between 2011 and 2021 after stratifying participants into three age groups. Furthermore, we analyzed the prevalence of ASD by birth year. Results: The highest level of prevalence appeared in children aged 6 years, and thereaf-ter, it declined with age. The prevalence of ASD in children aged 2 to 18 years in-creased from 0.05% in 2011 to 0.12% in 2021. During the same time, the prevalence in preschool children (2 to 5 years) remarkably increased from 0.04% in 2011 to 0.12% in 2021, while the prevalence in adolescents (13 to 18 years) increased from 0.05% in 2011 to 0.09% in 2021. The prevalence of ASD notably increased during the coronavirus dis-ease 2019 (COVID-19) pandemic (2020 to 2021). Among children born between 2011 and 2015, the prevalence of ASD was higher for children with recent birth years, espe-cially during the COVID-19 pandemic. Conclusion: The overall ASD prevalence in children and adolescents in Korea seems to be increasing, especially in preschool children during the COVID-19 pandemic. Early and more effective interventions are necessary for Korean children.

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Background/objectives: The prevalence of autistic spectrum disorder has been increasing rapidly in the world population and the cause of this increase is unknown. Autistic spectrum disorder is an important cause of social, communication and specific learning difficulties in children. Assortative mating may increase the genetic burden leading to manifestation of polygenic diseases affecting mental health in the offspring. Correlation of scores in the social responsiveness scale (SRS), which is used to quantify autistic spectrum disorder features, between spouses, has been used as indicator of phenotypic assortative mating. We investigated whether assortative mating is involved in increased severity of autism spectrum disorder in the offspring. Methods: All studies reporting on investigation of assortative mating in relationship to autistic spectrum disorder were included. Information sources were PubMed, EMBASE and the Cochrane Library. Results were synthesized by entering correlation analyses of results of the SRS conducted in spouses in a meta-analysis. A sub-group analysis was performed comparing spouses with offspring with diagnosed autistic spectrum disorder to spouses without. Prevalence of autistic spectrum disorders in children in countries with and without predominant assortative mating was compared. Results: A total of 14 investigations of assortative mating including 9914 spouse pairs were included. In total, 8 studies (4641 spouse pairs) reported intra-class correlation (ICC) or Spearman's correlation coefficients between spouses' SRS scores. There was a significant correlation of SRS scores in studies using ICC or Spearman's correlation with a pooled coefficient = 0.37. Spouse pairs (n = 401) with offspring diagnosed with autistic spectrum disorder had a pooled ICC coefficient which was 0.278 (95% CI 0.08 to 0.46), significantly lower than spouse pairs without (n = 1525): 0.40 (95% CI 0.35 to 0.46). Higher scores in SRS of both spouses were associated with higher scores and more autism diagnoses in offspring. Pooled prevalence of autistic spectrum disorder in children in countries where assortative mating is most common was 63.1 per 10,000 of population and in countries without it was significantly lower with 14.1 per 10,000 of population. Conclusions: There is evidence of assortative mating according to social responsiveness scale score which correlates significantly in spouse pairs with and without children with autistic spectrum disorder. In countries where assortative mating is predominant, a higher prevalence of autism spectrum disorder in children is found compared to countries without.

Early identification of children with autism spectrum disorder (ASD) facilitates timely access to intervention services. Yet, few population-based data exist on ASD identification among preschool-aged children. The authors aimed to describe ASD prevalence and characteristics among 4-year-old children in 5 of 11 sites participating in the 2010 Autism and Developmental Disabilities Monitoring Network. Children with ASD were identified through screening of health and education records for ASD indicators, data abstraction and compilation for each child, and clinician review of records. ASD prevalence estimates, ages at first evaluation and ASD diagnosis, cognitive test scores, and demographics were compared for 4-year-old children and 8-year-old children living in the same areas. Among 58,467 children in these 5 sites, 4-year-old ASD prevalence was 13.4 per 1000, which was 30% lower than 8-year-old ASD prevalence. Prevalence of ASD without cognitive impairment was 40% lower among 4-year-olds compared with 8-year-olds, but prevalence of ASD with cognitive impairment was 20% higher among 4-year-olds compared with 8-year-olds. Among 4-year-olds with ASD, female and non-Hispanic white children were more likely to receive their first comprehensive evaluation by age 36 months compared with male and non-Hispanic black children, respectively. Among children diagnosed with ASD by age 48 months, median age at first comprehensive evaluation was 27 months for 4-year-olds compared with 32 months for 8-year-olds. Population-based ASD surveillance among 4-year-old children provides valuable information about the early identification of children with ASD and suggests progression toward lowering the age of first ASD evaluation within participating Autism and Developmental Disabilities Monitoring communities.

Background: It is reported that there is increasing prevalence of autism spectrum disorder (ASD) in the world. Early recognition, diagnosis and intervention are known to be vital to improve the prognosis in children with ASD. In China, little research has been conducted on the knowledge of autism prevalence by child healthcare workers, or their attitude towards the traditional Chinese medical treatment of childhood ASD. Objectives: This study assessed the knowledge of autism prevalence and attitudes towards traditional Chinese medical treatment among child healthcare workers in grassroots health organizations in China. Methods: A total of 265 child healthcare workers were randomly selected in Chongqing, China. A socio-demographic questionnaire was administered to assess knowledge about autism prevalence as well as the attitudes towards the traditional Chinese medical treatment of childhood ASD. The correlations between socio-demographic variables and knowledge of childhood ASD were examined using univariate and multivariate analyses. Results: Out of 12 possible scores of knowledge about autism, mean score was 7.3 ± 2.19. Knowledge about childhood ASD was statistically associated with the education level, geographic region, the area of specialty and level of work experience with ASD. 38% of participants believed that ASD could be treated by traditional Chinese medicine. 79% of participants did not agree that the prevalence of childhood ASD in China was approximately 1%. Conclusions: The scores among child healthcare workers reflect deficits in knowledge about ASD. Therefore, education about childhood ASD is needed. Further studies on the effects of traditional Chinese medical treatment and a relatively accurate prevalence of ASD in China are needed.

The primary goal of our study is to assess the national US prevalence of autism spectrum disorder (ASD), along with its socio-demographic characteristics, severity, and co-occurring medical and psychiatric disorders, using data from the 2020-2021 National Survey of Children's Health (NSCH). We analyzed 2020-2021 NSCH data to estimate the prevalence of ever-diagnosed and current ASD among 79,182 children and adolescents (3-17 years). Univariate and multivariate regression models were used to examine associations between medical and psychiatric co-morbidities, socio-demographic factors, and ASD severity. Adolescents (11-17 years) and males were more likely to have ASD, with males comprising 78.7% of the ASD group. The mean age of the sample was 10.1 ± 4.6 years, and 3.2% had an ASD diagnosis. Children from lower-income households and those with caregivers who completed only a high school education were more likely to have ASD. Nearly 96.4% of children with ASD had at least one co-morbid condition. The most common neuropsychiatric co-morbidities were developmental delay (64%), behavioral and conduct problems (57.8%), and anxiety disorder (45.7%), while the most common medical conditions were allergies (32.4%), genetic disorders (26.2%), and asthma (12.6%). Gender disparities in ASD presentation were evident that females with ASD were more likely to experience vision problems, cerebral palsy, epilepsy, depression, and intellectual disability but had lower odds of ADHD and anxiety problems. Greater ASD severity was linked to higher odds of intellectual disability (OR: 5.8, p < 0.001), developmental delay (OR: 5.0, p < 0.001), epilepsy, Down syndrome (OR: 3.4, p < 0.001), vision problems (OR: 2.5, p < 0.001), and genetic disorders (OR: 2.3, p < 0.001). This study provides updated prevalence estimates of ASD and highlights the high burden of co-morbidities, emphasizing the need for comprehensive, multidisciplinary approaches in ASD management. Additionally, our findings emphasize gender differences in ASD presentation, which should be considered in future research and clinical practice to ensure more tailored diagnostic and intervention strategies.

Accurate estimation of annual changes in autism spectrum disorders (ASD) prevalence is critical for planning the expansion of diagnostic, education, and intervention services at an adequate rate. Previous studies from Israel have reported that ASD prevalence among 8-year-old children has increased from estimates of 0.3% in 2008 to 0.65% in 2015 and 1.3% in 2018. Here, we analyzed data acquired from the National Insurance Institute of Israeli (NII), a governmental organization that approves and monitors all ASD children who receive welfare services in Israel, and Clalit Health Services (CHS), the largest Health Maintenance Organization in Israel that provides health services to ~52% of the population. Data from both sources included annual data files from 2017 to 2021 containing the number of ASD cases per year of birth for 1-17-year-old children. This allowed us to estimate annual ASD prevalence among 3.5 million children born between 2000 and 2020 in Israel. Both data sources revealed a nearly two-fold increase in ASD prevalence among 1-17-year-old children from 2017 to 2021. Estimated prevalence rates differed across age groups with 2-3-year-old (day-care) children increasing from 0.27% to 1.19% (>4 fold change), 4-6-year-old (pre-school) children increasing from 0.8% to 1.83%, and 8-year-old children increasing from 0.82% to 1.56% in NII data. These results demonstrate that autism prevalence continues to increase in Israel with a shift towards diagnosis at earlier ages. These findings highlight the challenge facing health and education service providers in meeting the needs of a rapidly growing autism population.