Is Autism an Epidemic? What’s Behind the Numbers

The numbers are sobering: More than 3.5 million Americans are living with autism spectrum disorder (ASD), and its prevalence increased by a staggering 119 percent from 2000 to 2010, according to the Centers for Disease Control and Prevention (CDC).

The CDC says one in 68 children is now identified as being on the spectrum. For boys the prevalence of autism is 1 in 42, while for females the number decreases significantly to 1 in 189.

The idea of an autism epidemic has been around for many years. Some in the autism community believe it is indeed rampant. However, a closer look at the numbers and the factors at work reveal a more nuanced reality.

One answer to the rising numbers is pretty straightforward: Many of those now identified as being on the spectrum were actually there all along. It’s just that these individuals were previously overlooked, because they were either never diagnosed or they were misdiagnosed.

Heightened awareness in the medical community and the general public, has led to more babies and children being identified and older individuals, like teens and adults, to be belatedly diagnosed with ASD.

For babies and toddlers, earlier and better identification can be traced to The American Academy of Pediatrics which recommended in 2006 that screening all children for autism take place during routine pediatrician visits at 18 and 24 months of age.

This change opened the door to several diagnostic improvements:

  • Toddlers and children with mild symptoms, who might not have been identified previously, are now being diagnosed as on the autism spectrum
  • Clarification of autism criteria in the DSM-5 has led to better diagnosis on the part of clinicians – for example, children who are autistic may previously have been identified as having another disorder
  • The criteria for screening have also been broadened in newer editions of the DSM, causing more children to undergo screening.

These tweaks and changes in identification of ASD, “caused a drop in the number of parents who reported that their child has developmental delays, and a rise in the number reporting autism,” wrote Nicholette Zeliadt in “Spectrum Magazine.”

Paul Shattuck, PhD and autism researcher at Washington University in St. Louis, Missouri, calls these changes, “diagnostic substitution.”

In a school setting, Shattuck points out, “A kid labeled autistic today could have been labeled mentally retarded 10 years ago at the same school.”

Education, awareness, and better diagnostics can lead to significant changes.

One example is prostate cancer, which experienced a diagnosis increase of 100 percent from the years 1986 to 1992. This dramatic jump coincided, and was largely attributed to, an aggressive awareness campaign about the prostate cancer-screening program based on the Prostate Specific Antigen (PSA) test, which had been approved by the FDA in 1986.

“The take-away message,” said Glen Elliott, chief psychiatrist and medical director of Children’s Health Council in Palo Alto, CA, “is that at least a significant amount of the perceived increase of autism spectrum disorders is due to changes in criteria we use to make the diagnosis and the increased awareness about autism spectrum disorders that has led both to earlier diagnoses and greater likelihood of detection.”

And, there are other factors linked to an increase in the ASD numbers

  • Premature birth is a known autism risk factor, and more premature infants are surviving in greater numbers
  • Older parents, especially fathers, are another risk factor – and fertility advances have made it possible for many older adults to have biological children
  • The most recent CDC estimate of autism prevalence is based on the fourth edition of the DSM. Future estimates will be based on DSM-5, which contains different criteria about autism, and this may actually show lower autism rates
  • The way in which autism statistics are tabulated and analyzed may leave room for interpretation.

This last point is related to how the CDC determines autism rates in the U.S. Many assume that a nationwide sampling is conducted, but this is not the case.

Instead, every two years, CDC researchers collect the health and school records for eight-year-old children who reside in preselected counties located in 11 states across the U.S. Age eight is selected because children are enrolled in school, schools have had time to assess them, and they have undergone routine health screenings.

Trained clinicians then scan records for any autism traits – such as repetitive behavior and social issues—to determine if a child meets the criteria.

It’s important to point out four factors in the CDC evaluation process:

  • Children can be identified with ASD but no medical diagnosis is necessary
  • Kids who are home-schooled or reside in isolated locales are not incorporated into the survey
  • After the local records are screened, the results are extrapolated to the entire state
  • While this approach takes a real-time “snapshot” of children in a specific geographic area, it is also important to point out these children may not be fully representative of all children in the state.

Additionally, the CDC numbers show the rate of autism varies significantly from state to state. For example, autism prevalence in Colorado is 1 in 93 children as compared to the state of New Jersey where it is 1 in 41.

Eric Fombonne, professor of psychiatry at Oregon Health and Science in Portland, notes it is unlikely autism rates naturally vary that much between states. Instead, Fombonne theorizes the difference probably reflects varying levels of autism awareness and of services offered in those states.

The importance of both awareness and services is noted in a 2013 study that identified autistic children are “clustered” where resources for diagnosis and treatment were greater. In other words, where there’s better access to medical care, the autism rate is higher.

Research into the rise in autism rates is lacking in the U.S., but there have been studies in other parts of the world.

In Denmark, for example, a study of the health records of all children born between 1980 and 1991 – more than 667,000 – found that almost two thirds of the increase in autism can be traced to diagnosis and tracking. The research results, published in JAMA Pediatrics, concludes the “increase is likely more about previously-unidentified autistic individuals getting an autism diagnosis than more individuals actually developing autism.”

Another study, available on the National Institutes of Health (NIH) website is a 2011 study in South Korea, which found an autism prevalence of 1 in 38, or about 2.6 percent of the Korean population. This figure is considerably higher than our numbers in the U.S.

Still, for many here in the U.S. the autism numbers are still a concern.

Craig Newschaffer, PhD chairman and professor of the department of epidemiology and biostatistics at Drexel University School of Public Health in Philadelphia is an exception as he thinks the numbers actually help put autism into perspective. For many decades, “We thought autism was a very rare occurrence, and it’s clear that it’s not,” he said.

Many questions remain and the increase and autism cannot be fully interpreted and explained. Unfortunately for those living with the disorder and their families, there is not a tidy, neat, conclusive answer to some very important questions.

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