Prevalence and Characteristics of Autism Spectrum Disorder Among Children Aged 8 Years — Autism and Developmental Disabilities Monitoring Network, 11 Sites, United States, 2018

Problem/Condition: Autism spectrum disorder (ASD).Period Covered: 2018.Description of System: The Autism and Developmental Disabilities Monitoring (ADDM) Network conducts active surveillanceof ASD. This report focuses on the prevalence and characteristics of ASD among children aged 8 years in 2018 whose parents orguardians lived in 11 ADDM Network sites in 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 staffreview and abstract developmental evaluations and records from community medical and educational service providers. In 2018,children met the case definition if their records documented 1) an ASD diagnostic statement in an evaluation (diagnosis), 2) a specialeducation classification of ASD (eligibility), or 3) an ASD International Classification of Diseases (ICD) code.Results: For 2018, across all 11 ADDM sites, ASD prevalence per 1,000 children aged 8 years ranged from 16.5 in Missouri to38.9 in California. The overall ASD prevalence was 23.0 per 1,000 (one in 44) children aged 8 years, and ASD was 4.2 timesas prevalent among boys as among girls. Overall ASD prevalence was similar across racial and ethnic groups, except AmericanIndian/Alaska Native children had higher ASD prevalence than non-Hispanic White (White) children (29.0 versus 21.2 per 1,000children aged 8 years). At multiple sites, Hispanic children had lower ASD prevalence than White children (Arizona, Arkansas,Georgia, and Utah), and non-Hispanic Black (Black) children (Georgia and Minnesota). The associations between ASD prevalenceand neighborhood-level median household income varied by site. Among the 5,058 children who met the ASD case definition,75.8% had a diagnostic statement of ASD in an evaluation, 18.8% had an ASD special education classification or eligibility andno ASD diagnostic statement, and 5.4% had an ASD ICD code only. ASD prevalence per 1,000 children aged 8 years that wasbased exclusively on documented ASD diagnostic statements was 17.4 overall (range: 11.2 in Maryland to 29.9 in California).The median age of earliest known ASD diagnosis ranged from 36 months in California to 63 months in Minnesota.Among the 3,007 children with ASD and data on cognitive ability, 35.2% were classified as having an intelligence quotient (IQ)score ≤70. The percentages of children with ASD with IQ scores ≤70 were 49.8%, 33.1%, and 29.7% among Black, Hispanic,and White children, respectively. Overall, children with ASD and IQ scores ≤70 had earlier median ages of ASD diagnosis thanchildren with ASD and IQ scores >70 (44 versus 53 months).Interpretation: In 2018, one in 44 children aged 8 years was estimated to have ASD, and prevalence and median age of identificationvaried widely across sites. Whereas overall ASD prevalence was similar by race and ethnicity, at certain sites Hispanic children wereless likely to be identified as having ASD than White or Blackchildren. The higher proportion of Black children comparedwith White and Hispanic children classified as having intellectualdisability was consistent with previous findings.Public Health Action: The variability in ASD prevalence and community ASD identification practices among children with different racial, ethnic, and geographical characteristics highlights the importance of research into the causes of that variabilityand strategies to provide equitable access to developmental evaluations and services. These findings also underscore the need forenhanced infrastructure for diagnostic, treatment, and support services to meet the needs of all children.