Autism in 8-Year-Olds, 2016: One in 54 Children Across 11 U.S. Communities

In 2016, CDC's Autism and Developmental Disabilities Monitoring (ADDM) Network found autism spectrum disorder (ASD) in 18.5 per 1,000 children aged 8 — one in 54 — across 11 communities in the United States. That was about 10% higher than the network's 2014 estimate (16.8, one in 59), and about 2.8 times its first estimates from 2000 and 2002 (6.7, one in 150).

ASD is a developmental disability marked by lasting difficulties with social interaction and by restricted, repetitive behaviors, interests or activities.

How the network counts

The ADDM Network has reported ASD prevalence every even-numbered year since 2000, building on CDC tracking that began in metropolitan Atlanta in 1996. For 2016 it followed children born in 2008 whose parents or guardians lived in its sites:

1. Staff review records from medical, education and service providers — autism clinics, intervention providers and schools — and compile every evaluation (including IQ tests) of any child whose records mention ASD.
2. Experienced clinicians review each child's de-identified record and decide whether it meets a case definition based on the DSM-5.

Not every site could see school records, and the sites aren't nationally representative.

Prevalence by site

Autism prevalence by site and IQ. Image from CDC's report

New Jersey's rate was higher than every other site's. The two lowest, Colorado and Missouri, had limited or no access to education records. Of five sites that covered the same areas with the same case definition in 2014 and 2016, Maryland and Tennessee held steady while Arkansas, New Jersey and Wisconsin rose.

Boys and girls; race and ethnicity

• Boys: 29.7 per 1,000; girls: 6.9 — a ratio of 4.3 to 1, ranging from 3.4 to 4.7 across sites.
• White (18.5), Black (18.3) and Asian/Pacific Islander (17.9) children had nearly identical rates.
• Hispanic children were identified less often (15.4).

For the first time since the network began, there was no significant difference in overall ASD prevalence between Black and white children — a narrowing that may signal earlier, more equitable identification. Earlier ADDM reports found higher ASD rates in better-off groups and neighborhoods, suggesting ASD may be spotted more readily where families have good access to services.

Intellectual disability

Among children with ASD whose IQ information was available:

Intellectual disability ranged from 25% (New Jersey) to 42% (Georgia). It was more common in girls than boys, and in Black (47%) and Hispanic (36%) children than white children (27%).

Evaluation and diagnosis

Early treatment and services are linked to better outcomes, so timing matters.

Black children with ASD were more likely to have an intellectual disability — and children with one were more likely to be evaluated early — yet Black children were still less likely than white children to be evaluated by age 3. Among children with intellectual disability, Black children were diagnosed at a median 48 months, against 42 for white children.

How early autism was diagnosed at each site. Image from CDC's report

The median age at diagnosis has barely moved in ADDM's history, but the authors warn it can hide progress: if a community starts diagnosing children it once missed at older ages, the median goes up. Cumulative incidence — the share diagnosed by a given age — may show gains better. New Jersey diagnosed more children by age 3 than any other site, though its median age matched the network's. By age 8, 13.2 per 1,000 children had an ASD diagnosis.

Other ways of counting

The network's count beside the community's own. Image from CDC's report

Counting every child with an ASD diagnosis, school autism classification or ASD billing code gave 17.2 per 1,000 — about 7% lower than the network's 18.5, with sites in a similar order.

CDC's autism data site compares state figures from ADDM, the NSCH, Medicaid and special education. Most ADDM sites came in below the survey estimates — which may point to children still unidentified there.

What's next

The authors call for timely, accessible developmental assessments, educational supports and services, and for study of the community barriers that delay evaluation — comparing places that identify ASD early with those that don't. CDC's "Learn the Signs. Act Early." program works through Act Early Ambassadors to improve early identification. Later ADDM years (2018, 2020) will track 4- and 8-year-olds in 11 states, and five sites are following children identified at 8 to age 16.

Limits

• The count depends on records: sites without school records may miss children — especially Black or Hispanic children — served for ASD only at school, and incomplete records could undercount ASD.
• Sites are chosen competitively and aren't nationally representative.
• Network coverage has changed over time, which makes trends harder to read.

Sources

Based on Matthew J. Maenner, Kelly A. Shaw, Jon Baio and colleagues, "Prevalence of Autism Spectrum Disorder Among Children Aged 8 Years — Autism and Developmental Disabilities Monitoring Network, 11 Sites, United States, 2016," MMWR Surveillance Summaries, volume 69, Centers for Disease Control and Prevention, as corrected by a later erratum; a work of the United States government in the public domain. The report puts intellectual disability among girls with ASD at both 39% and 40%, so no figure for girls is given here.