Prevalence of autism spectrum disorder among children aged 8 years

Rates of autism spectrum disorder (ASD) have risen slightly in the United States, which may be because of to improved detection among minority populations, the US Centers for Disease Control and Prevention (CDC) said today.

According to the latest estimates, 1 in 59 children aged 8 years (16.8 per 1000) were diagnosed with ASD in 2014, up from 1 in 68 (14.6 per 1000) in 2012.

The latest estimates appear in the April 27 issue of the Morbidity and Mortality Weekly Report.

They stem from the CDC's Autism and Developmental Disabilities Monitoring (ADDM) Network, a tracking system that provides estimates of the prevalence and characteristics of ASD among 8-year-old children in 11 communities in Arizona, Arkansas, Colorado, Georgia, Maryland, Minnesota, Missouri, New Jersey, North Carolina, Tennessee, and Wisconsin. The latest estimates are based on data from a total population of 325,483 children aged 8 years, which represents 8% of the total US population of 8-year-olds.

Some of the uptick in ASD prevalence could be due to improved identification in minority populations, the CDC said. Although the disorder is still more likely to be identified in white children, autism prevalence among black and Hispanic children is "approaching that of white children," Stuart Shapira, MD, PhD, associate director for science at the CDC's National Center on Birth Defects and Developmental Disabilities, said in a news release.

"The higher number of black and Hispanic children now being identified with autism could be due to more effective outreach in minority communities and increased efforts to have all children screened for autism so they can get the services they need," Shapira said.

In the latest estimates, ASD prevalence was fourfold higher in boys than girls (26.6 vs 6.6 per 1000).

Among nine ADDM sites with sufficient data on intellectual ability, 31% of children with ASD were classified as having intellectual disability (IQ ≤70), 25% were in the borderline range (IQ 71–85), and 44% had IQ scores in the average to above average range (IQ >85).

Overall ASD prevalence varied widely among the 11 communities, ranging from 13.1 per 1000 in Arkansas to 29.3 per 1000 in New Jersey. Some of the regional differences in ASD prevalence estimates among the 11 communities could be due to differences in how ASD is diagnosed and documented, the CDC said.

Because ADDM sites do not provide a representative sample of the entire United States, these prevalence data can't be generalized to all US children aged 8 years, the CDC said. However, on the basis of these estimates, "the need for behavioral, educational, residential, and occupational services remains high, as does the need for increased research on both genetic and nongenetic risk factors for ASD," write Jon Baio, EdS, from the National Center on Birth Defects and Developmental Disabilities at the CDC, and colleagues.

A top priority remains identifying children with ASD at a younger age and referring them to early intervention. According to the CDC, fewer than half of the children identified in the ADDM Network were diagnosed by the time they were 4 years old. And although for 85% of children with ASD, concerns about development were noted in their health records by age 3 years, only 42% received a developmental evaluation by that age. This lag between first concern and first evaluation may cause delays in children receiving services.

Parents can track their child's development and act early if there is a concern. Healthcare providers can acknowledge and help parents act on those concerns. And those who work with or on behalf of children can join forces to ensure that all children with autism get identified and connected to the services they need as early as possible," Shapira said in the release.

The CDC's Learn the Signs. Act Early program provides parents, childcare professionals, and healthcare providers free resources, in English and Spanish, for monitoring children's development. The program offers parent-friendly, research-based milestone checklists for children as young as 2 months of age. The program also offers information about what to do if there is a developmental concern and whom to contact for assistance.

The next report from the ADDM Network will add data for children who were 8 years old in 2016. It will provide a clearer picture of whether ASD prevalence is changing and whether improvements are being made in early identification of autism.

https://www.medscape.com/viewarticle/895763

Baio J, Wiggins L, Christensen DL, Maenner MJ, Daniels J, Warren Z, Kurzius-Spencer M, Zahorodny W, Robinson Rosenberg C, White T, Durkin MS, Imm P, Nikolaou L, Yeargin-Allsopp M, Lee LC, Harrington R, Lopez M, Fitzgerald RT, Hewitt A, Pettygrove S, Constantino JN, Vehorn A, Shenouda J, Hall-Lande J, Van Naarden Braun K, Dowling NF. Prevalence of Autism Spectrum Disorder Among Children Aged 8 Years - Autism and Developmental Disabilities Monitoring Network, 11 Sites, United States, 2014. MMWR Surveill Summ. 2018 Apr 27;67(6):1-23.

Abstract

PROBLEM/CONDITION:

Autism spectrum disorder (ASD).

PERIOD COVERED:

2014.

DESCRIPTION OF SYSTEM:

The Autism and Developmental Disabilities Monitoring (ADDM) Network is an active surveillance system that provides estimates of the prevalence of autism spectrum disorder (ASD) among children aged 8 years whose parents or guardians reside within 11 ADDM sites in the United States (Arizona, Arkansas, Colorado, Georgia, Maryland, Minnesota, Missouri, New Jersey, North Carolina, Tennessee, and Wisconsin). ADDM surveillance is conducted in two phases. The first phase involves review and abstraction of comprehensive evaluations that were completed by professional service providers in the community. Staff completing record review and abstraction receive extensive training and supervision and are evaluated according to strict reliability standards to certify effective initial training, identify ongoing training needs, and ensure adherence to the prescribed methodology. Record review and abstraction occurs in a variety of data sources ranging from general pediatric health clinics to specialized programs serving children with developmental disabilities. In addition, most of the ADDM sites also review records for children who have received special education services in public schools. In the second phase of the study, all abstracted information is reviewed systematically by experienced clinicians to determine ASD case status. A child is considered to meet the surveillance case definition for ASD if he or she displays behaviors, as described on one or more comprehensive evaluations completed by community-based professional providers, consistent with the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, Text Revision (DSM-IV-TR) diagnostic criteria for autistic disorder; pervasive developmental disorder-not otherwise specified (PDD-NOS, including atypical autism); or Asperger disorder. This report provides updated ASD prevalence estimates for children aged 8 years during the 2014 surveillance year, on the basis of DSM-IV-TR criteria, and describes characteristics of the population of children with ASD. In 2013, the American Psychiatric Association published the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5), which made considerable changes to ASD diagnostic criteria. The change in ASD diagnostic criteria might influence ADDM ASD prevalence estimates; therefore, most (85%) of the records used to determine prevalence estimates based on DSM-IV-TR criteria underwent additional review under a newly operationalized surveillance case definition for ASD consistent with the DSM-5 diagnostic criteria. Children meeting this new surveillance case definition could qualify on the basis of one or both of the following criteria, as documented in abstracted comprehensive evaluations: 1) behaviors consistent with the DSM-5 diagnostic features; and/or 2) an ASD diagnosis, whether based on DSM-IV-TR or DSM-5 diagnostic criteria. Stratified comparisons of the number of children meeting either of these two case definitions also are reported.

RESULTS:

For 2014, the overall prevalence of ASD among the 11 ADDM sites was 16.8 per 1,000 (one in 59) children aged 8 years. Overall ASD prevalence estimates varied among sites, from 13.1-29.3 per 1,000 children aged 8 years. ASD prevalence estimates also varied by sex and race/ethnicity. Males were four times more likely than females to be identified with ASD. Prevalence estimates were higher for non-Hispanic white (henceforth, white) children compared with non-Hispanic black (henceforth, black) children, and both groups were more likely to be identified with ASD compared with Hispanic children. Among the nine sites with sufficient data on intellectual ability, 31% of children with ASD were classified in the range of intellectual disability (intelligence quotient [IQ] <70), 25% were in the borderline range (IQ 71-85), and 44% had IQ scores in the average to above average range (i.e., IQ >85). The distribution of intellectual ability varied by sex and race/ethnicity. Although mention of developmental concerns by age 36 months was documented for 85% of children with ASD, only 42% had a comprehensive evaluation on record by age 36 months. The median age of earliest known ASD diagnosis was 52 months and did not differ significantly by sex or race/ethnicity. For the targeted comparison of DSM-IV-TR and DSM-5 results, the number and characteristics of children meeting the newly operationalized DSM-5 case definition for ASD were similar to those meeting the DSM-IV-TR case definition, with DSM-IV-TR case counts exceeding DSM-5 counts by less than 5% and approximately 86% overlap between the two case definitions (kappa = 0.85).

INTERPRETATION:

Findings from the ADDM Network, on the basis of 2014 data reported from 11 sites, provide updated population-based estimates of the prevalence of ASD among children aged 8 years in multiple communities in the United States. The overall ASD prevalence estimate of 16.8 per 1,000 children aged 8 years in 2014 is higher than previously reported estimates from the ADDM Network. Because the ADDM sites do not provide a representative sample of the entire United States, the combined prevalence estimates presented in this report cannot be generalized to all children aged 8 years in the United States. Consistent with reports from previous ADDM surveillance years, findings from 2014 were marked by variation in ASD prevalence when stratified by geographic area, sex, and level of intellectual ability. Differences in prevalence estimates between black and white children have diminished in most sites, but remained notable for Hispanic children. For 2014, results from application of the DSM-IV-TR and DSM-5 case definitions were similar, overall and when stratified by sex, race/ethnicity, DSM-IV-TR diagnostic subtype, or level of intellectual ability.

PUBLIC HEALTH ACTION:

Beginning with surveillance year 2016, the DSM-5 case definition will serve as the basis for ADDM estimates of ASD prevalence in future surveillance reports. Although the DSM-IV-TR case definition will eventually be phased out, it will be applied in a limited geographic area to offer additional data for comparison. Future analyses will examine trends in the continued use of DSM-IV-TR diagnoses, such as autistic disorder, PDD-NOS, and Asperger disorder in health and education records, documentation of symptoms consistent with DSM-5 terminology, and how these trends might influence estimates of ASD prevalence over time. The latest findings from the ADDM Network provide evidence that the prevalence of ASD is higher than previously reported estimates and continues to vary among certain racial/ethnic groups and communities. With prevalence of ASD ranging from 13.1 to 29.3 per 1,000 children aged 8 years in different communities throughout the United States, the need for behavioral, educational, residential, and occupational services remains high, as does the need for increased research on both genetic and nongenetic risk factors for ASD.