By Carla K. Johnson
About 1 in 100 children has an autism disorder — higher than a previous U.S. estimate of 1 in 150, two new government studies indicate.
Greater awareness, broader definitions, and spotting autism in younger children may explain some of the increase, federal health officials said.
"The concern here is that buried in these numbers is a true increase," said Dr. Thomas Insel, director of the National Institute of Mental Health. "We're going to have to think very hard about what we're going to do for the 1 in 100."
Figuring out how many children have autism is extremely difficult because diagnosis is based on a child's behavior, said Dr. Susan E. Levy of the Children's Hospital of Philadelphia and a member of the American Academy of Pediatrics subcommittee on autism.
"With diabetes, you can get a blood test," Levy said. "As of yet, there's no consistent biologic marker we can use to make the diagnosis of autism."
The new estimate would mean about 673,000 American children have autism. Previous estimates were about 560,000.
One of the studies stems from the 2007 National Survey of Children's Health. The results were released Monday, and published in October's Pediatrics.
In that study, based on telephone surveys, parents reported about 1 in 91 children, ages 3 to 17, had autism, including milder forms such as Asperger's syndrome.
The findings are based on the results of a national telephone survey of more than 78,000 parents of children ages 3 to 17. The survey dealt with many health issues and included two questions on autism.
Parents were asked whether a doctor or other healthcare provider had ever told them that their child had autism, Asperger's syndrome, pervasive developmental disorder, or other autism spectrum disorder.
If parents said yes, they were asked whether their child has autism or an autism spectrum disorder now. "Yes" to both questions was counted as a child with an autism disorder.
The survey questions were flawed, said autism researcher Irva Hertz-Picciotto of the University of California, Davis. A broad definition, read to some parents who asked for clarification, didn't include "repetitive behaviors," Hertz-Picciotto said. And parents weren't asked about a professional diagnosis in the second question.
"The wording and definition invited much broader interpretation," Hertz-Picciotto said, and researchers didn't check what parents said against medical records.
In another finding, nearly 40 percent of the children ever diagnosed with autism disorders didn't have autism now, the parents reported. That rate is much higher than autism recovery researchers had found previously.
Outside experts said they doubt it reflects a true rate of recoveries. Autism could have been suspected and later ruled out for some of the children, the authors wrote.
One of the new study's authors was supported in part by a grant from Autism Speaks. The others work for federal agencies.
"Autism is a highly prevalent disorder," said Geraldine Dawson, chief science officer of the advocacy group Autism Speaks. "We're looking at a major public health challenge."
