Prevalence of Autism Spectrum Disorder Among Children Aged 8 Years - Autism and Developmental Disabilities Monitoring Network, 11 Sites, United States, 2016

Abstract

Problem/condition: Autism spectrum disorder (ASD).

Period covered: 2016.

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 whose parents or guardians live in 11 ADDM Network sites in the United States (Arizona, Arkansas, Colorado, Georgia, Maryland, Minnesota, Missouri, New Jersey, North Carolina, Tennessee, and Wisconsin). Surveillance is conducted in two phases. The first phase involves review and abstraction of comprehensive evaluations that were completed by medical and educational service providers in the community. In the second phase, experienced clinicians who systematically review all abstracted information determine ASD case status. The case definition is based on ASD criteria described in the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition.

Results: For 2016, across all 11 sites, ASD prevalence was 18.5 per 1,000 (one in 54) children aged 8 years, and ASD was 4.3 times as prevalent among boys as among girls. ASD prevalence varied by site, ranging from 13.1 (Colorado) to 31.4 (New Jersey). Prevalence estimates were approximately identical for non-Hispanic white (white), non-Hispanic black (black), and Asian/Pacific Islander children (18.5, 18.3, and 17.9, respectively) but lower for Hispanic children (15.4). Among children with ASD for whom data on intellectual or cognitive functioning were available, 33% were classified as having intellectual disability (intelligence quotient [IQ] ≤70); this percentage was higher among girls than boys (39% versus 32%) and among black and Hispanic than white children (47%, 36%, and 27%, respectively) [corrected]. Black children with ASD were less likely to have a first evaluation by age 36 months than were white children with ASD (40% versus 45%). The overall median age at earliest known ASD diagnosis (51 months) was similar by sex and racial and ethnic groups; however, black children with IQ ≤70 had a later median age at ASD diagnosis than white children with IQ ≤70 (48 months versus 42 months).

Interpretation: The prevalence of ASD varied considerably across sites and was higher than previous estimates since 2014. Although no overall difference in ASD prevalence between black and white children aged 8 years was observed, the disparities for black children persisted in early evaluation and diagnosis of ASD. Hispanic children also continue to be identified as having ASD less frequently than white or black children.

Public health action: These findings highlight the variability in the evaluation and detection of ASD across communities and between sociodemographic groups. Continued efforts are needed for early and equitable identification of ASD and timely enrollment in services.

FIGURE 1

Prevalence* of autism spectrum disorder among children aged 8 years, by most recent intelligence quotient score and site — Autism and Developmental Disabilities Monitoring Network, 10 sites,^† United States, 2016 Abbreviations: ADDM = Autism and Developmental Disabilities Monitoring Network; IQ = intelligence quotient. * Per 1,000 children aged 8 years. ^† Missouri is not included because it did not collect IQ information on at least 60% of children with ASD. The total numbers of children with ASD, by site: n = 537 (Colorado), n = 606 (Arkansas), n = 405 (Tennessee), n = 282 (Arizona), n = 579 (Wisconsin), n = 456 (Georgia), n = 192 (Maryland), n = 313 (Minnesota), n = 489 (North Carolina), and n = 1,036 (New Jersey).

FIGURE 2

Cumulative incidence* of autism spectrum disorder diagnoses,^† by age and site — Autism and Developmental Disabilities Monitoring Network, 11 sites, United States, 2016 Abbreviations: ADDM = Autism and Developmental Disabilities Monitoring Network; ASD = autism spectrum disorder; ICD = International Classification of Diseases. * Per 1,000 children aged 8 years. ^† These data only include the portion of ADDM Network ASD cases with a documented diagnostic statement of ASD in the record. Children counted as ADDM Network cases without a documented ASD diagnosis (i.e., does not consider special education classifications or ICD codes) are not included.

FIGURE 3

Comparison of autism spectrum disorder prevalence*^,† on the basis of Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition, criteria and community-identified^§ autism spectrum disorder prevalence, by site and overall — Autism and Developmental Disabilities Monitoring Network, 11 sites, United States, 2016 Abbreviations: ADDM = Autism and Developmental Disabilities Monitoring Network; ASD = autism spectrum disorder; DSM-5 = Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition; ICD = International Classification of Diseases. * Per 1,000 children aged 8 years. ^† The dots represent prevalence estimates and the vertical lines bounded by bars represent the corresponding 95% confidence intervals. ^§ Children are considered to be identified as having ASD by the community if they have an autism diagnosis stated in an evaluation, have been determined to meet autism eligibility in special education, or have been assigned an autism ICD code. Missouri, Colorado, and Wisconsin had limited access to information from educational records.