A new government survey of parents indicates that 1 in 50 school-age children have autism spectrum disorder (ASD). This is significantly higher than the official government estimate of 1 in 88 American children. It also supports research suggesting that many affected children are being missed by the surveillance methods the Centers for Disease Control (CDC) uses to produce its official estimate.
The CDC’s 1 in 88 estimate of autism prevalence is based on medical and school records of 8-year-old children at monitoring sites across the country. As such, it misses children who are not receiving medical or special education services related to autism. The new 1 in 50 estimate comes from a 2011-2012 telephone survey that asked nearly 100,000 parents across the country a range of health-related questions about children ages 6 to 17.
"This number does not replace the official 1 in 88 estimate, but does suggest that it may be a significant underestimate of autism prevalence in the U.S.," says Autism Speaks Associated Director of Public Health Research Michael Rosanoff, M.P.H. “One in fifty, or 2 percent, is much closer to what we’ve seen from research that involves directly screening children in the community.”
Rosanoff refers to a 2011 report, funded by Autism Speaks, which directly screened for autism among schoolchildren in South Korea. It found a prevalence of 1 in 38, or 2.64 percent. Autism Speaks and the CDC are now collaborating on a similar direct screening study in South Carolina. (Read more about the South Korea study here and the South Carolina study here.)
Among the new survey’s surprising findings was that many children were being diagnosed with autism after age 7. That's 5 years or more after autism can be reliably diagnosed. “Many kids appear to be flying under the radar and may be in regular classrooms,” Rosanoff says. “It is possible that these children are struggling in areas of life and school, and could benefit from access to appropriate services.”
In addition, children with milder symptoms are the most likely to be affected by upcoming changes to the diagnostic definition of autism, slated to take effect in May. These new DSM-5 criteria will collapse the previously separate subtypes of autism into a unifying diagnosis of autism spectrum disorder (ASD). Preliminary research suggests that the DSM-5 definition will reliably capture most children with autism. However, it may miss some on the milder end of the spectrum. As a science and advocacy organization, Autism Speaks is taking a proactive role in monitoring the diagnostic changes to ensure that all children who need autism-related services receive them.
The full report, “Changes in Prevalence of Parent-Reported Autism Spectrum Disorder in School-Aged Children: 2007 to 2011-2012” is available here.
For more perspective on what these findings mean for the autism community, read this letter from Autism Speaks President Liz Feld and this blog by Autism Speaks board member and autism self-advocate John Elder Robison.