At-a-Glance

CDC data from 2018 estimated that 1 in 44 eight-year-old children in the U.S. have a diagnosis of autism.

Background: Every two years, the Autism and Developmental Disabilities Monitoring (ADDM) Network estimates how prevalent autism is among children who are 4- and 8-years-old. Through this monitoring program, the Centers for Disease Control and Prevention (CDC) can evaluate how well early identification programs are functioning, how these programs are being used by different groups of people, and whether there are demographic changes in the population of individuals identified with ASD. Over time, the ADDM Network has reported decreasing prevalence differences between groups, suggesting more equitable identification (e.g., similar rates of autism detected among Black and White children), but other disparities remain. This study focuses on the ADDM Network's monitoring of 8-year-old children.

Methods & Findings: In 2018, the ADDM Network had sites in 11 states. The data from these sites was used to estimate the local autism prevalence of children born in 2010. These sites found that 1 in 44 children who were 8 years of age had documented autism (meaning they either received formal diagnosis, were eligible for school services, or their medical records were coded for autism). Boys were more than 4 times as likely to have an ASD diagnosis than girls. Rates of autism were similar among White, Black, Hispanic, and Asian/Pacific Islander children. Not enough data were available to determine the prevalence of autism among American Indian/Alaskan Native children. Thirty-five percent of children identified with autism were also documented as having an intellectual disability. Black autistic children were more likely to be classified as having an intellectual disability than White autistic children. Nearly half (47%) of children with documented autism had been evaluated by 3 years of age, and the median age at earliest diagnosis was 50 months. Autistic children who had intellectual disability were diagnosed earlier than autistic children without intellectual disability. Findings from some-but not all-states suggested that children from lower-income neighborhoods were more likely to have documented autism than children from higher-income areas.

Implications: These findings indicate an overall higher prevalence of autism than was reported in previous years, suggesting an overall improvement in identification. The findings also suggest, however, that disparities in access to autism identification services continue among certain groups, in addition to geographic differences in prevalence. For example, while overall rates of autism across all ADDM sites is similar, in certain states, autism in Hispanic children is evaluated and identified less frequently than in other children. Some recorded disparities (e.g., the high rate of intellectual disability among autistic Black children) suggest a need for increased research into how race and other demographic factors intersect with autism diagnosis and characteristics. Increased work is needed to reduce disparities in identification of and support for children with autism.

At-a-Glance

CDC data from 2018 estimate that 1 in 59 four-year-old children in the U.S. have a diagnosis of autism and that children are being identified earlier.

Background: Every two years, the CDC's Autism and Developmental Disabilities Monitoring (ADDM) Network estimates how prevalent autism is among children who are 4- and 8-years-old. This network also monitors the earliest age these children were first documented as or suspected of having autism. By comparing children of different ages, this program can track historical trends, including potential improvements in early identification of autism. In addition, this approach allows the CDC to determine whether access to autism-related evaluation and care is similar among different demographic groups. This study focuses on the ADDM Network's monitoring of 4-year-old children.

Methods & Findings: In 2018, the ADDM Network had sites in 11 states. The data from these sites was used to estimate the local autism prevalence in children born in 2014. Four-year-old boys were almost 3.5 times more likely to be documented as having autism than girls. Asian/Pacific Islander children were the most likely to have autism, followed by Hispanic, Black, White, and American Indian/Alaskan Native children. Children living in lower-income areas were also more likely to have autism. Approximately half of children identified with autism were also classified as having intellectual disability. Children whose records contained a qualified professional's statement indicating a possibility of autism but were not formally diagnosed were less likely to have a documented intellectual disability. Intellectual disability was higher among Black autistic children than among White, Asian/Pacific Islander, and Hispanic autistic children, all of whom had similar rates. Approximately 72% of children with a formal ASD diagnosis had their first evaluation by age 36 months. The prevalence was similar among boys and girls and by racial and ethnic groups but did vary by site. Early identification improved relative to the previous year of analysis in 2016. Moreover, compared to children born in 2010, children born in 2014 were 1.5 times more likely to be diagnosed with autism by 4 years of age. In addition, this study finds that for the first time, ASD prevalence was higher among Asian/Pacific Islander, Hispanic, and Black children than among White children.

Implications: Given the increased likelihood of early evaluation among children born in 2014 relative to those born in 2010, it appears that early autism identification is improving over time. This was found to be particularly true among populations that historically were less likely to receive appropriate evaluation, such as low-income and non-White groups. The year 2018 was also the first time in which enough data were recorded for Asian/Pacific Islander and American Indian/Alaskan Native children to be included in the analyses. In addition, identification rates increased among Asian/Pacific Islander, Black, and Hispanic children and children from families with lower income. However, autistic children with intellectual disability were more likely to be identified than autistic children without intellectual disability, particularly among Black children. Additionally, the differences in prevalence of autism in four-year-old children compared to eight-year-old children suggest that many children are identified with autism later than four years of age. Therefore, more work is needed to provide timely and equitable access to early autism identification services.