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March 30, 2012

CDC Releases New Report on Autism Prevalence in U.S.

Researchers at the Johns Hopkins Bloomberg School of Public Health contributed to a new Centers for Disease Control and Prevention (CDC) report that estimates the prevalence of Autism Spectrum Disorders (ASD) as affecting 1 in 88 U.S. children overall, and 1 in 54 boys. 

This is the third such report by the CDC’s Autism and Developmental Disabilities Monitoring Network (ADDM), which has used the same surveillance methods for more than a decade.  Previous ADDM reports estimated the rate of ASDs at 1 in 110 children in the 2009 report that looked at data from 2006, and 1 in 150 children in the 2007 report, which covered data from 2002.  The current prevalence estimate, which analyzed data from 2008, represents a 78 percent increase since 2002, and a 23 percent increase since 2006.

ASDs include diagnoses of autistic disorder, Asperger disorder, and Pervasive Developmental Disorder-Not Otherwise Specified (PDD-NOS).  ASDs encompass a wide spectrum of conditions, all of which affect communication, social and behavioral skills.  The causes of these developmental disorders are not completely understood, although studies show that both environment and genetics play an important and complex role. There is no known cure for ASDs, but studies have shown that behavioral interventions, particularly those begun early in a child’s life, can greatly improve learning and skills.

The latest CDC report, “Prevalence of Autism Spectrum Disorders – Autism and Developmental Disabilities Monitoring Network, 14 Sites, United States, 2008,” provides autism prevalence estimates from different areas of the United States, including Maryland.  The purpose of the report is to provide high-quality data on the extent and distribution of ASDs in the U.S. population, to promote better planning for health and educational services, and to inform the further development of research on the causes, progression, and treatments.

“We continue observing increases in prevalence since the inception of the project in 2000,” said Li-Ching Lee, PhD, a psychiatric epidemiologist with the Bloomberg School"s Departments of Epidemiology and Mental Health and the principal investigator for the prevalence project’s Maryland site.  “In Maryland, we found 27 percent of children with ASDs were never diagnosed by professionals. So, we know there are more children out there and we may see the increase continue in coming years.”

The new report, which focuses on 8-year-olds because that is an age where most children with ASD have been identified, shows that the number of those affected varies widely among the 14 participating states, with Utah having the the highest overall rate (1 in 47) and Alabama the lowest (1 in 210).  Across all sites, nearly five times as many boys as girls are affected.  Additionally, growing numbers of minority children are being diagnosed, with a 91 percent increase among black non-Hispanic children and a 110 percent increase for Hispanic children.  Researchers say better screening and diagnosis may contribute to those increases among minority children.

The overall rate in Maryland is 1 in 80 children;  1 in 49 boys and 1 in 256 girls.  In Maryland, the prevalence has increased 85 percent from 2002 to 2008. The increase was 41 percent between 2004 and 2008, and 35 percent between 2006 and 2008.

The data were gathered through collaboration with the Maryland State Department of Education and participating schools in Anne Arundel, Baltimore, Carroll, Cecil, Harford and Howard counties, as well as clinical sources such as Kennedy Krieger Institute, Mt. Washington Pediatric Hospital, and University of Maryland Medical System.

While the report focuses on the numbers, its authors acknowledge that the reasons for the increase are not completely understood and that more research is needed.  They note that the increase is likely due in part to a broadened definition of ASDs, greater awareness among the public and professionals, and the way children receive services in their local communities. “It’s very difficult, if not impossible, to tease these factors apart to quantify how much each of these factors contributed to the increase,” Dr. Lee said.

But whatever the cause, “This report paints a picture of the magnitude of the condition across our country and helps us understand how communities identify children with autism. One thing the data tell us with certainty – there are more children and families that need help,” said CDC Director Thomas Frieden, MD, MPH.

Researchers also identified the median age of ASD diagnosis, documented in records. In Maryland, that age was 5 years and 6 months, compared with 4 years, 6 months nationally.   Across all sites, children who have autistic disorder tend to be identified earlier, while those with Asperger Disorder tend to be diagnosed later.  Given the importance of early intervention, ADDM researchers carefully track at what age children receive an ASD diagnosis.

“Unfortunately, most children still are not diagnosed until after they reach age 4. We’ve heard from too many parents that they were concerned long before their child was diagnosed.  We are working hard to change that,” said Coleen Boyle, PhD, MSHyg, director of CDC’s National Center on Birth Defects and Developmental Disabilities.

To see the full report:  http://www.cdc.gov/mmwr/preview/mmwrhtml/ss6103a1.htm?s_cid=ss6103a1_w

To the Community Report with state statistics: http://www.cdc.gov/ncbddd/autism/documents/ADDM-2012-Community-Report.pdf

Media contact for Johns Hopkins Bloomberg School of Public Health: Natalie Wood-Wright at 410-614-6029 or nwoodwri@jhsph.edu