How Has Autism Prevalence Changed Over Time?
Joan Lipuscek
While combing through the Centers for Disease Control and Prevention's (CDC) Data & Statistics site for Autism Spectrum Disorder, we came across an interesting data table with a list of historical prevalence studies for autism among children and teens from around the globe.
The following visualization provides a summary of average prevalence rates of autism for children and teens through the decades starting in the 1960's. There has been a sharp increase in the rise of autism in children and teens as reported through these various international studies since the 1980's. For the most recent studies conducted since 2011, the average rate of prevalence of autism among children and teens is about 1%.
After clicking on a specific decade or switching to the second tab labeled "Autism by Study", we have graphed the prevalence rates of all autism studies listed in the table since 1966. (Please set your browser to allow third party cookies if you receive an error while trying to explore the data.)
OBSERVATIONS
We observe that the 1999 study of Swedish children, "Brief report: Autism and Asperger Syndrome in Seven-Year-Old Children: A Total Population Study" by Kadesjo et al. published in the Journal of Autism and Developmental Disorders, Vol. 29, No. 4, 1999 was particularly prescient. Despite discovering the highest rate of prevalence of any study on our list at the time of publication, prevalence rates from other countries began to drift higher throughout the 2000's.
To date, the South Korean study, "Prevalence of Autism Spectrum Disorders in a Total Population Sample" by Kim et al. published in the American Journal of Psychiatry, 2013 has found the highest prevalence rate of autism among children and teens of any study on our list at 2.6% or 1 in 38.
The most recent U.S. study on our list, "Changes in Prevalence of Parent-reported Autism Spectrum Disorder in School-aged U.S. Children: 2007 to 2011–2012" by Blumberg et al. reported the highest U.S. prevalence rate of autism among children and teens to date at 2.0%.
Although not included in the CDC's list of autism studies that we worked from, the more recent "Estimated Prevalence of Autism and Other Developmental Disabilities Following Questionnaire Changes in the 2014 National Health Interview Survey" by Zablotsky et al. confirmed this higher rate in the U.S. with a finding of a 2.2% prevalence rate among children and teens.
It is generally agreed that at least part of the increase in autism is due to a broader definition of the disorder and greater efforts in diagnosis. However, the CDC has not ruled out the possibility that the overall number of children and teens with autism has been increasing in the past two decades. To answer this question, the CDC is currently working on the Study to Explore Early Development (SEED) to help better identify the factors that put children at risk for autism and other developmental disabilities.