Progress and Disparities in Early Identification of Autism Spectrum Disorder: Autism and Developmental Disabilities Monitoring Network, 2002-2016

Abstract

Objective: Early identification can improve outcomes for children with autism spectrum disorder (ASD). We sought to assess changes in early ASD identification over time and by co-occurring intellectual disability (ID) and race/ethnicity.

Method: Using data for 2002-2016 from a biennial population-based ASD surveillance program among 8-year-old children in the United States, we defined identification as a child's earliest recorded ASD diagnosis or special education eligibility. Unidentified children had characteristics meeting the ASD surveillance case definition but no recorded identification by age 8 years. We calculated median age at identification among identified children, median age at identification including unidentified children, and cumulative incidence of identification by age 48 months.

Results: ASD identification by age 48 months was 4 times (95% CI: 3.6-4.3) as likely in 2016 as in 2002, with the largest increases among children without ID. Median age at ASD identification among identified children decreased 3 months during this time. Children of every race/ethnicity were more likely to be identified over time. There were racial disparities stratified by ID: in 2016, Black and Hispanic children without ID were less likely to be identified with ASD than were White children (both groups risk ratio: 0.7; 95% CI: 0.5-0.8), but Black children were 1.5 times (95% CI: 1.3-1.9) as likely as White children to be identified with ASD and ID.

Conclusion: Substantial progress has been made to identify more children with ASD early, despite minimal decrease in median age at diagnosis. Considerable disparities remain in early ASD identification by race/ethnicity and co-occurring intellectual disability.

Keywords: autism spectrum disorder; epidemiology; health status disparities; intellectual disability.

FIGURE 1

Early Identification of Autism Spectrum Disorder (ASD) Using 3 Metrics Note: In the first panel, the gray line indicates the age in months at which 50% of children with recorded autism spectrum disorder (ASD) diagnosis or special education eligibility were identified (median among identified children). In the second panel, the line indicates the age in months at which 50% of children with and without recorded ASD were identified (median including unidentified children). In the third panel, the line indicates cumulative incidence of ASD identified by age 48 months per 1,000 children. Data are from the Autism and Developmental Disabilities Monitoring Network from 2002–2016.

FIGURE 2

Cumulative Incidence of Early-Identified Autism Spectrum Disorder (ASD) Identification by Site Note: Cumulative incidence is by age 48 months per 1,000 children. Limited to 9 sites that participated in the Autism and Developmental Disabilities Monitoring Network each surveillance year from 2008–2016.

FIGURE 3

Three Metrics of Early Identification of Autism Spectrum Disorder (ASD) by Presence of Co-occurring Intellectual Disability (ID) Note: Limited to sites with IQ data in Autism and Developmental Disabilities Monitoring Network surveillance reports from 2002–2016; excludes children with unknown ID case status. The first panel shows the median among identified children, which is the age in months at which 50% of children with recorded ASD diagnosis or special education eligibility were identified. The second panel shows the median including unidentified children, which is the age in months at which 50% of children with and without recorded ASD were identified. The third panel shows cumulative incidence of ASD identified by age 48 months per 1,000 children.

FIGURE 4

Difference in Autism Spectrum Disorder (ASD) Incidence in 2016 Compared to 2002 for Each Month of Age and by Co-occurring Intellectual Disability (ID) Note: Limited to sites with IQ data in Autism and Developmental Disabilities Monitoring Network surveillance reports; excludes children with unknown ID case status.

FIGURE 5

Cumulative Incidence of Early-Identified Autism Spectrum Disorder (ASD) by Race/Ethnicity and Co-occurring Intellectual Disability (ID) in 2002 and 2016 Note: Cumulative incidence is by age 48 months per 1,000 children. Limited to sites with IQ data in Autism and Developmental Disabilities Monitoring Network surveillance reports; excludes children with unknown ID case status.