CHICAGO (AP) - A study in South Korea suggests about 1 in 38 children have traits of autism, higher than a previous U.S. estimate of 1 in 100.
By casting a wider net and looking closely at mainstream children, the researchers expected to find a higher rate of autism characteristics. But they were surprised at how high the rate was.
Autism often goes undiagnosed, study authors say
They don't think South Korea has more children with autism than the United States, but instead that autism often goes undiagnosed in many nations. U.S. estimates are based on education and medical records, not the more time-consuming survey conducted in South Korea.
"Our study does not suggest that Koreans have more autism than any other place in the world. Our study does suggest that method that you use to count autism makes a whole lot of difference," said Roy Grinker, senior author of the study and an anthropologist at George Washington University.
Michael Robinson was one of those undiagnosed children. He was 18 months old when his mother Marjorie first noticed unusual behavior.
"I called his name, he didn't turn around. I'd have to call his name again and again," she said. She feared Michael might be autistic.
"He'd open and close doors for hours. He would just open and close them, (there was) nothing I could do to get him to stop," she described.
She said doctors pushed off her suspicion. "I was blatantly told by two or three doctors that he does not have autism."
Robinson said she and her husband started intense treatment before her son was finally diagnosed at three years old. Six years later, he is in a regular school class, has friends and sleepover, Robinson said.
Still, she believes an earlier diagnosis would have helped.
"I think we need to get a better handle on the prevalence," she said.
Undiagnosed children often had mild impairments, study found
Two-thirds of the children with autism traits in the study were in the mainstream school population, hadn't been diagnosed before and weren't getting any special services. Many of those undiagnosed children likely have mild social impairments, rather than more severe autism.
"It doesn't mean all of a sudden there are more new children with (autism spectrum disorders)," said co-author Dr. Young-Shin Kim of the Yale Child Study Center. "They have been there all along, but were not counted in previous prevalence studies."
It's not clear whether the children need special services or not, other experts said.
"I'm sure some of these children probably could benefit from intervention, but I don't think we could make a statement that all would benefit from intervention," said Dr. Marshalyn Yeargin-Allsopp, chief of the Centers for Disease Control and Prevention's developmental disabilities branch.
The CDC wasn't involved in the new study, although another federal agency, the National Institute of Mental Health, provided some funding. The group, Autism Speaks, which advocates for more aggressive autism screening, also helped pay for the study. Autism Speaks had no role in the study's design.
The research, published Monday in the American Journal of Psychiatry, attempted to screen all 55,000 schoolchildren, ages 7 to 12, in a district of Goyang City, near Seoul.
Questionnaire and additional testing to diagnose autism traits
However, only about two-thirds of mainstream children participated. About 63 percent of their parents filled out a survey. The researchers acknowledged that parents of affected children might be more likely to fill out the survey.
The questionnaire used is a recognized screening tool for high-functioning autism such as Asperger's syndrome. It asks such questions as whether the child "stands out as different" in a number of ways, including lacking empathy, lacking best friends and being bullied by other children.
From there, some of the children who screened positive were tested further. Very few of the children actually completed the entire diagnosis process. But the researchers say they still were able to use the findings to estimate that about 2.6 percent of the population had some autism traits - compared to the U.S. estimateof 1 percent.
The ambitious study took five years to complete. The U.S. government's approach is quicker and allows more ongoing results, Yeargin-Allsopp said.
"Community providers, researchers and others are interested in prevalence of autism on a frequent basis," Yeargin-Allsopp said. "This is not possible if you're doing a screening of an entire population" as was attempted by the South Korean researchers.
Other funders of the study were Children's Brain Research Foundation and the George Washington University Institute for Ethnographic Research.