Summary: 1 in 22 children in California is diagnosed with autism, a new study reports. The number is higher than previous estimates in December which stated 1 in 44 children were on the autism spectrum. Earlier diagnosis and extensive early services may account for the higher number of children diagnosed with ASD in California.
A new report from the Centers for Disease Control and Prevention (CDC) shows the rates and demographics of children with autism spectrum disorder (ASD) are changing in the United States.
In the latest analysis, 1 in 36 8-year-old children (2.8%) have been identified as having ASD. This figure is higher than the previous estimate published in December 2021, which found a prevalence of 1 in 44 (2.3%) children, and considerably higher than the CDC’s first autism prevalence report published in 2007 noting a prevalence of 1 in 150 (0.7%).
Prevalence estimates also differed across the 11 data collection sites, ranging from 1 in 43 children (2.3%) in Maryland, to 1 in 22 (4.5%) in California. A second report examined 4-year-old children in the same 11 communities and found similarly high rates of autism (2.2%) in the network overall, and 4.6% in California in particular.
The findings were published on March 23, 2023 in the CDC’s Morbidity and Mortality Weekly Report (MMWR) Surveillance Summaries. All data were collected in 2020 by the Autism and Developmental Disabilities Monitoring (ADDM) Network, a program funded by the CDC to better understand the number and characteristics of children with ASD in the United States.
The network surveys 8-year-old and 4-year-old children in 11 communities across Arizona, Arkansas, California, Georgia, Maryland, Minnesota, Missouri, New Jersey, Tennessee, Utah and Wisconsin. The California ADDM site is based at UC San Diego and reports on ASD within San Diego County.
Early Identification in California
In addition to the overall prevalence of ASD, the ADDM Network also tracks the age of first autism diagnosis. The median age of first autism diagnosis for 8-year-olds across the entire network was 49 months, or just over 4 years. However, in California, the age of first diagnosis was much lower at 36 months, or 3 years.
“California is unique because of the intense focus on early detection and extensive early services,” said study co-author Karen Pierce, PhD, professor at UC San Diego School of Medicine, co-director of the UC San Diego Autism Center of Excellence and principal investigator of the ADDM California site.
“Some children in San Diego are diagnosed with autism by their second birthday and connected to services quickly thereafter. This is great news because the sooner they can be connected to services and support, the more likely they are to thrive in school and in later life.”
Racial and Ethnic Disparities
In contrast to all previous CDC reports, wherein white children were identified with ASD more often than non-white children, this is the first year that overall rates of ASD were consistently higher among Black (2.9%), Hispanic (3.2%) and Asian or Pacific Islander (3.3%) children compared to white (2.4%) children. This was also found in California where there were no differences found between racial and ethnic groups in California 8- and 4-year-olds.
“This first-of-a-kind finding is exciting because it suggests a movement towards equity in services for all children on the spectrum,” said Pierce.
Narrowing the Gender Gap
Historically, boys have been diagnosed with autism 4 to 5 times more often than girls. The latest report finds this gap is narrowing, as more girls have been identified with ASD than in years past, and the ratio between boys and girls has decreased in the ADDM Network overall.
Specifically, boys are now identified 3.8 and 3.1 times more often for the 8- and 4-year-old cohorts, respectively. This is also the first ADDM Network report in which the prevalence of ASD among girls has exceeded 1%. This trend of increasing identification of females with ASD was also found in California.
While ADDM is not a representative sample of the entire United States, the report provides significant insight into rates of diagnosis across the country, and highlights the importance of community access to early identification services.
For those seeking more information on ASD diagnoses, the CDC’s “Learn the Signs. Act Early” program provides free resources in English, Spanish and other languages to monitor children’s development starting at 2 months of age.
Their Milestone Tracker Mobile app can also help parents and caregivers track their child’s development and share the information with their healthcare providers.
About this autism research news
Author: Nicole Mlynaryk
Contact: Nicole Mlynaryk – UCSD
Image: The image is in the public domain
Original Research: Open access.
“Prevalence and Characteristics of Autism Spectrum Disorder Among Children Aged 8 Years — Autism and Developmental Disabilities Monitoring Network, 11 Sites, United States, 2020” by Karen Pierce et al. MMWR Morbidity and Mortality Weekly Report
“Early Identification of Autism Spectrum Disorder Among Children Aged 4 Years — Autism and Developmental Disabilities Monitoring Network, 11 Sites, United States, 2020” by Karen Pierce et al. MMWR Morbidity and Mortality Weekly Report
Prevalence and Characteristics of Autism Spectrum Disorder Among Children Aged 8 Years — Autism and Developmental Disabilities Monitoring Network, 11 Sites, United States, 2020
Problem/Condition: Autism spectrum disorder (ASD).
Period Covered: 2020.
Description of System: The Autism and Developmental Disabilities Monitoring (ADDM) Network is an active surveillance program that provides estimates of the prevalence of ASD among children aged 8 years. In 2020, there were 11 ADDM Network sites across the United States (Arizona, Arkansas, California, Georgia, Maryland, Minnesota, Missouri, New Jersey, Tennessee, Utah, and Wisconsin). To ascertain ASD among children aged 8 years, ADDM Network staff review and abstract developmental evaluations and records from community medical and educational service providers. A child met the case definition if their record documented 1) an ASD diagnostic statement in an evaluation, 2) a classification of ASD in special education, or 3) an ASD International Classification of Diseases (ICD) code.
Results: For 2020, across all 11 ADDM sites, ASD prevalence per 1,000 children aged 8 years ranged from 23.1 in Maryland to 44.9 in California. The overall ASD prevalence was 27.6 per 1,000 (one in 36) children aged 8 years and was 3.8 times as prevalent among boys as among girls (43.0 versus 11.4). Overall, ASD prevalence was lower among non-Hispanic White children (24.3) and children of two or more races (22.9) than among non-Hispanic Black or African American (Black), Hispanic, and non-Hispanic Asian or Pacific Islander (A/PI) children (29.3, 31.6, and 33.4 respectively). ASD prevalence among non-Hispanic American Indian or Alaska Native (AI/AN) children (26.5) was similar to that of other racial and ethnic groups. ASD prevalence was associated with lower household income at three sites, with no association at the other sites.
Across sites, the ASD prevalence per 1,000 children aged 8 years based exclusively on documented ASD diagnostic statements was 20.6 (range = 17.1 in Wisconsin to 35.4 in California). Of the 6,245 children who met the ASD case definition, 74.7% had a documented diagnostic statement of ASD, 65.2% had a documented ASD special education classification, 71.6% had a documented ASD ICD code, and 37.4% had all three types of ASD indicators. The median age of earliest known ASD diagnosis was 49 months and ranged from 36 months in California to 59 months in Minnesota.
Among the 4,165 (66.7%) children with ASD with information on cognitive ability, 37.9% were classified as having an intellectual disability. Intellectual disability was present among 50.8% of Black, 41.5% of A/PI, 37.8% of two or more races, 34.9% of Hispanic, 34.8% of AI/AN, and 31.8% of White children with ASD. Overall, children with intellectual disability had earlier median ages of ASD diagnosis (43 months) than those without intellectual disability (53 months).
Interpretation: For 2020, one in 36 children aged 8 years (approximately 4% of boys and 1% of girls) was estimated to have ASD. These estimates are higher than previous ADDM Network estimates during 2000–2018. For the first time among children aged 8 years, the prevalence of ASD was lower among White children than among other racial and ethnic groups, reversing the direction of racial and ethnic differences in ASD prevalence observed in the past. Black children with ASD were still more likely than White children with ASD to have a co-occurring intellectual disability.
Public Health Action: The continued increase among children identified with ASD, particularly among non-White children and girls, highlights the need for enhanced infrastructure to provide equitable diagnostic, treatment, and support services for all children with ASD. Similar to previous reporting periods, findings varied considerably across network sites, indicating the need for additional research to understand the nature of such differences and potentially apply successful identification strategies across states.
Early Identification of Autism Spectrum Disorder Among Children Aged 4 Years — Autism and Developmental Disabilities Monitoring Network, 11 Sites, United States, 2020
Problem/Condition: Autism spectrum disorder (ASD).
Period Covered: 2020.
Description of System: The Autism and Developmental Disabilities Monitoring Network is an active surveillance program that estimates prevalence and characteristics of ASD and monitors timing of ASD identification among children aged 4 and 8 years. In 2020, a total of 11 sites (located in Arizona, Arkansas, California, Georgia, Maryland, Minnesota, Missouri, New Jersey, Tennessee, Utah, and Wisconsin) conducted surveillance of ASD among children aged 4 and 8 years and suspected ASD among children aged 4 years. Surveillance included children who lived in the surveillance area at any time during 2020. Children were classified as having ASD if they ever received 1) an ASD diagnostic statement in an evaluation, 2) a special education classification of autism (eligibility), or 3) an ASD International Classification of Diseases (ICD) code (revisions 9 or 10). Children aged 4 years were classified as having suspected ASD if they did not meet the case definition for ASD but had a documented qualified professional’s statement indicating a suspicion of ASD. This report focuses on children aged 4 years in 2020 compared with children aged 8 years in 2020.
Results: For 2020, ASD prevalence among children aged 4 years varied across sites, from 12.7 per 1,000 children in Utah to 46.4 in California. The overall prevalence was 21.5 and was higher among boys than girls at every site. Compared with non-Hispanic White children, ASD prevalence was 1.8 times as high among Hispanic, 1.6 times as high among non-Hispanic Black, 1.4 times as high among Asian or Pacific Islander, and 1.2 times as high among multiracial children. Among the 58.3% of children aged 4 years with ASD and information on intellectual ability, 48.5% had an IQ score of ≤70 on their most recent IQ test or an examiner’s statement of intellectual disability. Among children with a documented developmental evaluation, 78.0% were evaluated by age 36 months. Children aged 4 years had a higher cumulative incidence of ASD diagnosis or eligibility by age 48 months compared with children aged 8 years at all sites; risk ratios ranged from 1.3 in New Jersey and Utah to 2.0 in Tennessee.
In the 6 months before the March 2020 COVID-19 pandemic declaration by the World Health Organization, there were 1,593 more evaluations and 1.89 more ASD identifications per 1,000 children aged 4 years than children aged 8 years received 4 years earlier. After the COVID-19 pandemic declaration, this pattern reversed: in the 6 months after pandemic onset, there were 217 fewer evaluations and 0.26 fewer identifications per 1,000 children aged 4 years than children aged 8 years received 4 years earlier. Patterns of evaluation and identification varied among sites, but there was not recovery to pre-COVID-19 pandemic levels by the end of 2020 at most sites or overall. For 2020, prevalence of suspected ASD ranged from 0.5 (California) to 10.4 (Arkansas) per 1,000 children aged 4 years, with an increase from 2018 at five sites (Arizona, Arkansas, Maryland, New Jersey, and Utah). Demographic and cognitive characteristics of children aged 4 years with suspected ASD were similar to children aged 4 years with ASD.
Interpretation: A wide range of prevalence of ASD by age 4 years was observed, suggesting differences in early ASD identification practices among communities. At all sites, cumulative incidence of ASD by age 48 months among children aged 4 years was higher compared with children aged 8 years in 2020, indicating improvements in early identification of ASD. Higher numbers of evaluations and rates of identification were evident among children aged 4 years until the COVID-19 pandemic onset in 2020. Sustained lower levels of ASD evaluations and identification seen at a majority of sites after the pandemic onset could indicate disruptions in typical practices in evaluations and identification for health service providers and schools through the end of 2020. Sites with more recovery could indicate successful strategies to mitigate service interruption, such as pivoting to telehealth approaches for evaluation.
Public Health Action: From 2016 through February of 2020, ASD evaluation and identification among the cohort of children aged 4 years was outpacing ASD evaluation and identification 4 years earlier (from 2012 until March 2016) among the cohort of children aged 8 years in 2020 . From 2016 to March 2020, ASD evaluation and identification among the cohort of children aged 4 years was outpacing that among children aged 8 years in 2020 from 2012 until March 2016. The disruptions in evaluation that coincided with the start of the COVID-19 pandemic and the increase in prevalence of suspected ASD in 2020 could have led to delays in ASD identification and interventions. Communities could evaluate the impact of these disruptions as children in affected cohorts age and consider strategies to mitigate service disruptions caused by future public health emergencies.