A new report on autism prevalence rates isn’t generating many headlines.
“There was not a statistically significant change in the prevalence of children ever diagnosed with autism spectrum disorder from 2014 to 2016.”
Zablotsky et al on Estimated Prevalence of Children With Diagnosed Developmental Disabilities in the United States, 2014–2016
While the rate seemed to increase on paper, from 2.24 to 2.76%, it was not a statistically significant change. If it had been a statistically significant change, then you could think autism rates really were increasing and the report would have made headlines beyond anti-vaccine websites.
“By trying to say that there is no significant increase, is the government hoping to reassure people that autism isn’t a significant problem? That the rising number of children with autism isn’t something that anyone has to worry about? Are they trying to avoid a panic?”
Dr. Bob Sears
As most people likely understand, the term significant is used in the report as a statistical term.
When something is found to be statistically significant, then you can be fairly confident that it wasn’t caused by chance alone.
“Significance is a statistical term that tells how sure you are that a difference or relationship exists.”
What does “statistical significance” really mean?
So by stating that “there was not a statistically significant change in the prevalence of children ever diagnosed with autism spectrum disorder,” they were not “trying to avoid a panic.” There is no conspiracy.
Reports About Autism Rates
Another thing to keep in mind as you think about this report – there are multiple reports about autism prevalence rates that come out every few years.
The latest report uses National Health Interview Survey data that was collected by the National Center for Health Statistics.
Unlike the autism prevalence reports from the Autism and Developmental Disabilities Monitoring (ADDM) Network that we are used to, which reported a rate of 1 in 68 children in 2016, the NCHS reports:
rely on parent reports during a telephone survey – one of the questions that they are asked is if a health professional has ever told them that their child has autism, but that diagnosis is not confirmed by looking at medical or school records
- are prone to recall bias – parents might not accurately recall what doctors have told them in the past about their child
- have questions that have changed over the years, for example, when PDD was added in 2014, it was thought that it might have confused some parents who didn’t know that a pervasive developmental disorder is different than a developmental disorder
- look at lifetime prevalence
And not surprisingly, over the years, the NHIS has typically reported higher autism rates than the Autism and Developmental Disabilities Monitoring Network.
So what does this new report on autism prevalence mean?
It means the same thing that all of the other recent reports have been saying, that autism prevalence rates seem to be unchanged.
What to Know About Autism Rates
After increasing for several years, autism rates seem to be unchanged, but that hasn’t kept anti-vaccine folks from trying to get parents to panic about changes in prevalence rates that are not statistically significant.
More on Autism Rates
- How Common is Autism?
- CDC – Autism and Developmental Disabilities Monitoring (ADDM) Network
- MMWR – Prevalence and Characteristics of Autism Spectrum Disorder Among Children Aged 8 Years — Autism and Developmental Disabilities Monitoring Network, 11 Sites, United States, 2012 (2016 report)
- NCHS – Estimated Prevalence of Children With Diagnosed Developmental Disabilities in the United States, 2014–2016
- NCHS – Estimated Prevalence of Autism and Other Developmental Disabilities Following Questionnaire Changes in the 2014 National Health Interview Survey.
- NSCS – ASD Data on the Data Resource Center
- NSCS – Prevalence of Autism – 2011/12 National Survey of Children’s Health
- No, the autism “rate” in California did not go down after removing thimerosal from vaccines
- Why Were Cases Of Autism So Hard To Find Before The 1990s?
- No, the autism prevalence did not go down in Denmark after the removal of thimerosal
- Autism prevalence is reported to be 1 in 50, and the antivaccine movement goes wild…again
- U.S. Autism Rate Unchanged in New CDC Report
- Is the Rise In Autism Rates Real?
- Evidence against an “autism epidemic”
Last Updated on December 13, 2017 by Vincent Iannelli, MD