The Centers for Disease Control and Prevention estimates that about 1 in 68 U.S. children has autism spectrum disorder, according to findings published March 27 in the agency’s Morbidity and Mortality Weekly Report. This is a 30% increase from CDC’s estimate of 1 in 88 children, using 2008 data.
The findings also show that autism spectrum disorder (ASD) continues to be more prevalent in boys than in girls: 1 in 42 boys had ASD in the latest report, compared with 1 in 189 girls (MMWR Surveill. Summ. 2014 March 27;63:1-21).
The increased prevalence could be attributed to improved clinician identification of autism, a growing number of autistic children with average to above-average intellectual ability, or a combination, Dr. Coleen Boyle, director of CDC’s National Center on Birth Defects and Developmental Disabilities (NCBDDD), said in a teleconference.
Dr. Coleen Boyle
CDC looked at 2010 data collected by its Autism and Developmental Disabilities Monitoring (ADDM) Network, which provides population-based estimates of ASD prevalence in children aged 8 years in 11 different sites in the United States, based on records from community sources that diagnose and provide services to children with developmental disabilities.
Of the 11 sites studied, 7 had information available on intellectual ability of at least 70% of children with ASD. Of the 3,604 children with available data, 31% were classified as having intellectual disability (IQ of 70 or below), 23% were considered borderline (IQ = 71-85), and 46% had IQ scores of greater than 85, considered average or above average intellectual ability.
"We recognize now that autism is a spectrum, no longer limited to the severely affected," added Dr. Marshalyn Yeargin-Allsopp, a pediatrician who is chief of the developmental disabilities branch of NCBDDD. "There are children with higher IQs being diagnosed, who may not even be receiving special education services, and the numbers may reflect that."
Non-Hispanic white children were 30% more likely to be identified with ASD than non-Hispanic black children, and were about 50% more likely to have ASD than Hispanic children.
Dr. Boyle stressed the importance of early screening and identification of ASD in children (ASD can be diagnosed by the time a child reaches age 2 years), and urged parents to take action if a child shows any signs of developmental delays.
"Community leaders, health professionals, educators, and childcare providers should use these data to ensure children with autism spectrum disorder are identified as early as possible and connected to the services they need," Dr. Boyle said at the teleconference.
To help promote early intervention in ASD, CDC will be launching an awareness initiative called "Birth to Five, Watch Me Thrive," which aims to provide parents, teachers, and community members with information and resources about developmental milestones and screening for autism.
"Most children with autism are not diagnosed until after age 4 years," she said. "CDC will continue to promote early identification and research. The earlier a child is identified and connected with services, the better."
CDC cited several limitations to the report. First, the surveillance sites were not selected to be representative of the entire United States. Second, population denominators used for this report were based on the 2010 decennial census, and comparisons with previous ADDM findings should be interpreted with caution, as ADDM reports from nondecennial surveillance years are likely influenced by greater error in the population denominators used for those previous surveillance years, which were based on post census estimates. Third, three of the nine sites with access to review children’s education records did not receive permission to do so in all school districts within the site’s overall surveillance area. Fourth, findings that address intellectual ability might not be generalizable to all ADDM sites. Finally, race and ethnicity are presented in very broad terms and should not be interpreted as generalizable to all persons within those categories.
The ADDM Network is funded by CDC. No other disclosures were reported.