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Determining and Monitoring Autism Prevalence in San Diego

The CDC’s Autism and Developmental Disabilities Monitoring Network

The Autism and Developmental Disabilities Monitoring (ADDM) Network is a collaborative network of programs funded by the Centers for Disease Control and Prevention (CDC) to estimate and track the number and characteristics of children with Autism Spectrum Disorder (ASD) and other developmental disabilities living in different areas of the United States. In order to provide accurate, population-based estimates of prevalence, ADDM Network sites work with community sources to review health and education records of children living within the geographic area of a participating site during the years under consideration.

Over the last 20 years, the CDC has funded ADDM Network sites in 17 different states. California is the most recent award site. Based out of the University of California San Diego’s Autism Center of Excellence, the CA site will be focusing on prevalence estimates in San Diego County.
Other current participating sites include:
  • University of ArizonaADDM Network Sites
  • University of Wisconsin System
  • Johns Hopkins University
  • University of Minnesota
  • Rutgers, The State University of New Jersey
  • University of Arkansas System
  • University of Utah
  • Vanderbilt University Medical Center
  • Washington University in St. Louis
Karen Pierce, PhD, is the principle investigator of the CA site.

What We’ve Found

On March 26, 2020, the CDC released the most recent national prevalence reports for children aged 4 and 8 years. These reports were based on data from 2016. Sites from eleven different states participated in the 2016 review of 8 year olds: Arkansas, Arizona, Colorado, Georgia, Maryland, Minnesota, Missouri, New Jersey, North Carolina, Tennessee, and Wisconsin. Review of 4 year olds in 2016 was completed by sites in Arizona, Colorado, Missouri, New Jersey, North Carolina, and Wisconsin.
Prevalence Estimates Over TimeThe 2020 report determined an overall ASD prevalence rate for eight year olds to be 1 in 54 (1.85%) and ranged from 1.31% to 3.1%. This prevalence rate continues the upward trend in ASD prevalence as demonstrated in prior reports. ASD was 4.3 times as prevalent among boys as girls. ASD occurs among all racial, ethnic, and socioeconomic groups. For the first time, ADDM found no overall difference in the number of black children identified with ASD compared to white children. However, the number of Hispanic children identified with ASD is still lower compared to white or black children The median age of first diagnosis—the age by which half of the children had their first professional diagnosis—was 51 months (range 38 to 57 months). However, the median age of first comprehensive evaluation—the age by which half of the children had a professional evaluation— was 40 months (range 29 to 46 months). Forty four percent of children had their first evaluation by 36 months of age (Healthy People 2020 goal is 47%).
For those children aged 4 years, the 2020 report determined an overall ASD prevalence rate to be 1 in 64 (1.56%). ASD was 3.5 times as prevalent among boys as girls. The median age of first comprehensive evaluation for the 4 years olds was 26 months, and the median age for first ASD diagnosis was 33 months. Eighty four percent of the 4 year olds had their first evaluation before 36 months of age.

Comparing Data Across Sources

The ADDM Network is not alone in the effort to understand how many families are impacted by ASD. Other programs, including the National Survey of Children’s Health (NSCH), the National Health Interview Survey (NHIS), the Centers for Medicare and Medicaid Services (CMS), and the US Department of Education (USDE), to name a few, are all working to determine ASD prevalence. Because each program collects data in a different way, the prevalence estimates vary across the different programs. For example, the US Department of Education reports on the number of children who receive special education and related services under the primary disability category for ASD, while CMS data is based on Medicaid billing codes, and both the NSCH and NHIS are based on parent/caregiver report of a professional diagnosis. The ADDM Network, however, utilizes a comprehensive, multiple source, records-based population surveillance system. Each site works with local health, education, and early intervention providers to determine the number of children with ASD in their community and to understand the characteristics of those children in order to better understand what it means to have an Autism Spectrum Disorder. 
The ADDM Network maintains a data visualization tool that can be used to examine, not only the ADDM data, but also data from the other organizations working on prevalence data. Prevalence rates from each organization vary considerably due to how and from whom they collect data.

Would You Like to Learn More?

To learn more about the CDC’s Learn the Signs, Act Early campaign visit:
Andrea Grzybowski


​Contact Andrea Grzybowski, MS, our CDC ADDM Project Manager, if you or your organization would like more information on how you can be a part of this important work.


Office Phone: 858-534-6910