This study examined changes in the administrative prevalence of autism spectrum disorders (ASD) in Utah children from 2002 to 2008 by record source (school and health), age (four, six, and eight), and special education classification. Prevalence increased 100% with 1 in 77 children aged eight identified with ASD by 2008. Across study years and age groups rates were higher when health and school data were combined with a greater proportion of cases ascertained from health. The proportion of children with both a health ASD diagnosis and a special education autism classification did not significantly change. Most children with an ASD health diagnosis did not have an autism special education classification. Findings highlight the growing health and educational impact of ASD.
Pinborough-Zimmerman and colleagues looked at de-identified medical and education records in Utah’s three most populous counties – Davis, Salt Lake, and Utah counties. They looked for specific diagnostic codes in medical records that indicated a child had been referred to a health care provider for ASD. In education records, they looked at whether a child had been classified with autism by a team of educational specialists.
The researchers discovered that ASD prevalence steadily increased throughout the study period, but varied with the age group studied. Prevalence was lower in younger children, suggesting that continued efforts to improve earlier diagnosis and treatment are needed. Prevalence rates also varied depending on the record used. Prevalence rates based on health records alone were significantly higher than those based on education records alone. The highest prevalence rate was found when health and education sources were used together.
"After all this work we still don’t know what the true prevalence of autism is in Utah," said Judith Pinborough-Zimmerman, the study’s lead author and research assistant professor in the University of Utah’s Department of Psychiatry. "We are only capturing kids that have a previous diagnosis. There may be many children and adults who have autism and still haven’t been diagnosed."
Utah’s rate appears to be higher than the national average: The latest national figures are from 2006 and show the rate among 8-year-olds was 1 in 111. The national figures are expected to be updated by the summer.
It’s unclear why Utah’s numbers have doubled: A change in the diagnostic criteria, increased awareness and better diagnostic tools may have contributed to the rise.
But that doesn’t fully explain the increase, said Jocelyn Taylor, one of the study authors and an autism education specialist at the Utah State Office of Education.
"As I interview teachers, I have veterans, teachers who have been teaching 20 or 30 years who say they’ve never seen anything quite like this," Taylor said. "While there may be better recognition of autism, there seems to be more autism."