autism prevalence Archives - Keep Kids Healthy

A new report on autism prevalence rates isn’t generating many headlines.

Why?

“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.

Unlike Dr. Bob and some others, they were simply trying to not mislead people into thinking that the change from 2.24 to 2.76% meant something that it did not.

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:

The National Health Interview Survey question about autism.

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

We hear stories about the rise in autism and the autism epidemic all of the time.

Autism prevalence rates have been steady at 1 in 68 since 2010.

Every few years, the CDC had been releasing a new report which showed a higher prevalence of autism in the United States, including:

1 in 150 children in 2000
1 in 150 children in 2002
1 in 125 children in 2004
1 in 110 children in 2006
1 in 88 children in 2008
1 in 68 children in 2010
1 in 68 children in 2012

Looking at those numbers, it is easy to see most people think that the rate of autism is rising.

And if the rate of autism is rising, then there must be a cause.

Thinking about it like that, it becomes easy to see why vaccines became the scapegoat for causing autism, especially after Andrew Wakefield told everyone that it “is my feeling, that the, the risk of this particular syndrome developing is related to the combined vaccine, the MMR…”

The Myth of an Autism Epidemic

Many experts don’t think that there is an autism epidemic though.

“…the numbers of people born with autism aren’t necessarily increasing dramatically. It’s just that we’re getting better and better at counting them.”

Emily Willingham

There are several different explanations for the apparent rise in the number of children being diagnosed with autism, including:

better recognition among health care providers
better recognition among parents
diagnostic substitution – children were once diagnosed with other conditions, such as mental retardation and learning disabilities
broadening of the criteria used to diagnose autism, including changes in DSM criteria, which went from labeling children with autism as having childhood schizophrenia (1952) and including just three essential features of infantile autism (1980) to adding PDD-NOS (1987) and more subtypes and symptoms to the autism diagnosis category in DSM-IV (1994).
social influences, including that more parents may have wanted to seek help when more resources become available and because they may have become more accepting of the possibility that their child had autism, leading them to seek a diagnosis and services. For example, before 1975 and the Education for All Handicapped Children Act, children with disabilities were excluded from school. And then in 1990, the Individuals with Disabilities Education Act (IDEA) included autism as a separate disability, making it a little easier to get services.

All together, these explanations help explain what has been confirmed by numerous studies, that the true prevalence of autism hasn’t changed over time.

What To Know About The Autism Epidemic Myth

There is no autism epidemic.

There are adults and older people with autism. Did you know that the the first meeting of the National Society of Autistic Children was held in 1965?
The idea that the ‘autism epidemic’ is a myth is not new – experts have been talking about it for over 10 years, which makes you wonder why some people still push the idea. An idea that hurts autistic families.
A 2015 study concluded that “Changes in reporting practices can account for most (60%) of the increase in the observed prevalence of ASDs in children born from 1980 through 1991 in Denmark. Hence, the study supports the argument that the apparent increase in ASDs in recent years is in large part attributable to changes in reporting practices.”
Autism is thought to be genetically based.

Some folks, especially those in the anti-vaccine movement, don’t want to believe that there is no autism epidemic though.

“If there is no autism epidemic, if there is a “stable incidence” of autism over recent decades, then this alone is powerful evidence against the vaccine hypothesis – and in fact removes the primary piece of evidence for a vaccine-autism connection.”

Steven Novella on The Increase in Autism Diagnoses: Two Hypotheses

After all, if there is no autism epidemic, then they can’t blame vaccines for be causing an autism epidemic…

Tag: autism prevalence