One in 88 children in the United States is now diagnosed with an autism spectrum disorder that makes social interactions and communication more difficult, according to new estimates released Thursday by the federal Centers for Disease Control and Prevention.
Previously, the CDC estimated the prevalence of autism spectrum disorders at about 1 in 110 children.
The new numbers suggest the developmental disability is 23% more common than thought two years ago, and 78% more common than estimated six years ago. The new numbers are based on a 2008 snapshot from autism monitoring sites in 14 states, including Wisconsin.
The largest increases nationwide were among Hispanic and black children. It's unclear whether the increases reflect better awareness, leading to diagnosis and access to ser vices, or true increases in the prevalence of autism spectrum disorders.
In the 10 southeastern Wisconsin counties included in the CDC study, autism identification was estimated at 1 in 128 children, lower than the national average.
Wisconsin's numbers may be artificially low, according to the principal investigator for the state's data collection.
That's because the state Department of Public Instruction declined to make school records available for data analysis, said Maureen Durkin, a professor of population health sciences and pediatrics at the University of Wisconsin-Madison School of Medicine and Public Health, who has been working with the CDC autism monitoring network since 2002.
Children who are economically disadvantaged are more likely to be identified at school as having an autism spectrum disorder, Durkin said. Milwaukee County recorded about half the prevalence of autism as other southeastern Wisconsin counties in the study, which Durkin attributed to the lack of access to school records.
Four other states did not release school records for the CDC analysis, but the prevalence of autism wasn't consistently lower in those states, Durkin said.
"It's a much bigger problem than we had recognized," Durkin said. "Whether it's better detection or an actual increase in the number of children with autism spectrum disorders, it's there, and there's a need for more research and services."
Those with autism spectrum disorders handle information in their brain differently, and the disorders can range from mild to severe. The three types of autism spectrum disorders include "classic autism," Asperger's syndrome (usually milder than classic autism) and Pervasive Developmental Disorder -- Not Otherwise Specified (also called atypical autism).
Doctors are getting better at diagnosing autism, CDC director Thomas Frieden said in a teleconference with reporters on Thursday. Communities also are getting better at providing services for children with autism, he said.
"The increase in identification could entirely be a result of better detection," Frieden acknowledged.
More children with higher cognitive abilities also are being identified as having an autism spectrum disorder, said Coleen Boyle, director of the CDC's National Center on Birth Defects and Developmental Disabilities.
"But you study to see if there's another cause," Boyle said.
Seeking explanations
Nothing has changed in the definition of autism that would explain the increased prevalence, said Amy Vaughan Van Hecke, an assistant professor of psychology at Marquette University and director of the Marquette Autism Clinic and Project.
