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CDC Report on Autism Suggests Changes to Survey Questions Impacts Reported Cases of Autism

First Posted: Nov 16, 2015 04:25 PM EST
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Between 2013 and 2014, the prevalence of autism doubled for young people in the U.S., but plunged for U.S. Hispanic youth. The shift in rates could be attributed to changes in environmental factors, pharmaceuticals or advances in research, or it could simply be attributed to changes to survey questions, affecting estimations of developmental disabilities.

Behavioral and developmental disabilities tend to be characterized by complications related to the brain or senses, and involve genetic disorders that impact multiple body systems, behavior and cognition. The Centers for Disease Control and Prevention published findings Nov. 13, indicating the prevalence of autism has doubled over the past three years. The parent survey, which led to the study's results, examined study-based estimates of the lifetime prevalence of autism, intellectual disability and other developmental disabilities. Researchers randomly selected families to be answer detail questions on functional limitations, health conditions and health care utilization. Parents were also asked if they'd ever had their children assessed by a health professional, or if they'd been told their children had developmental disabilities.

The primary objective of the report was to evaluate if changes to National Health Interview Survey (NHIS) questions on development issues impacted estimations of developmental disabilities in the U.S. in 2014. The greatest challenges to estimating prevalence include changes to definition and labeling, as well as co-occurring conditions that could to be prescribed to a number of developmental disabilities.

Between 1997 and 2010, professionals and parents consulted a 10-condition checklist to identify autism in children. From 2011 to 2013, the checklist continued to be used but wording was changed. For example, "autism" was changed to "autism/autism spectrum disorder. In 2014, the autism spectrum disorder (ASD) survey item became an independent question. Questions were revised to match terms included in the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, Text Revision. Estimates on intellectual delay and developmental delay were also examined. Additionally, functional limitations (ex. vision, walking, remembering) and receipt of selected services (ex. early intervention services, receiving special education) were examined.

According to the report, autism rates increased among U.S. children. In 2014, the estimated autism spectrum disorder prevalence rate was 2.24 percent (1 in 45), spiking since 2013, when the average was 1.25 percent (1 in 80). At the same time, development delays have decreased significantly (4.84 percent compared to 3.57 percent). Also, intelligence delays also dipped, though slightly (1.27 percent compared to 1.10 percent). For Hispanic youth, autism prevalence dropped (20.3 percent in 2013 and 16.1 percent in 2014).

The report shared the characteristic of children with autism, which remained the same before and after the survey changed. Overwhelmingly, children with autism tend to be male. In 2011-2013, 81.7 percent of autistic children were male, and 75 percent were male in 2014. In 2011-2013, 58.9 percent of autistic children were non-Hispanic white; and in 2014, 59.9 percent were non-Hispanic white. Also, in 2014 autistic children are more likely to live in large metropolitan areas (54.7), have two parents (68 percent), and have at least one parent with more than a high school level education (54.7). There has been a significant decrease in the number of autistic children who were also diagnosed with other developmental delays. However, there was no change in the likelihood of autistic children also having ADHD, intellectual delays or a learning disability.

For nearly 20 years, the CDC has been tracking autism prevalence and supports the Autism and Developmental Disabilities Monitoring (ADDM) Network. The report concludes with the assertion that changes to ordering and working of developmental disability questions led to changes to parent-reported prevalence of ASD. A report published by the CDC in 2014 offers that prevalence in the U.S. is estimated at 1 in 68 births.

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