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Federal health authorities have significantly raised their estimate of the prevalence of autism in children, concluding in a new study of 8-year-olds that 1 in 88 has some form of the disorder and that its prevalence has risen nearly 80 percent over the last decade.
For the analysis, released Thursday, researchers scoured tens of thousands of health and special education records in 14 states, looking for an autism diagnosis or the symptoms that would add up to one. It is the latest in a series of studies by the Centers for Disease Control and Prevention showing autism rates climbing dramatically over the past decade. The previous estimate was 1 in 110.
The new figure, based on 2008 data, is sure to fuel debate over whether a growing environmental threat could be at work. But autism researchers around the country said the CDC data -- including striking geographic and racial variations in the rates and how they have changed -- suggest that rising awareness of the disorder, better detection and improved access to services can explain much of the surge, and perhaps all of it.
Some experts questioned the validity of relying on records to estimate the disorder's true prevalence. David Mandell, an autism expert at the University of Pennsylvania, said the CDC's numbers primarily reflect the degree to which the diagnosis and services have taken hold in different places and among different groups.
"As the diagnosis is associated with more and more services, this becomes a less and less rigorous way to determine the prevalence of autism," he said, referring to the CDC's methods.
The federal agency found that Utah, which has widespread screening programs, had the highest rate -- 1 child in 47. The state was closely followed by New Jersey, which prides itself on its autism services, at 1 in 49. At the bottom was Alabama, one of the poorest states in the country. Its autism rate actually fell 20 percent between 2006 and 2008 -- from 1 in 167 to 1 in 208.
CDC officials acknowledged the limitations of their analysis. In surveillance areas where researchers had access only to health records and not school records, prevalence estimates were generally lower.
The researchers hope, however, that the study will draw attention to the need for more vigorous early screening. Research shows that early intervention offers autistic children the best long-term prospects. More than a fifth of children identified as autistic by the CDC had no autism diagnosis in their records.
Dr. Coleen Boyle, director of the CDC's National Center on Birth Defects and Developmental Disabilities, said that children "still aren't being identified enough."
Nobody knows what causes autism, and there is no blood test or other biological marker. It is diagnosed by its symptoms -- social and communication difficulties starting in early childhood as well as repetitive behaviors or abnormally intense interests -- and has come to include a wide range of children. Ultimately, a diagnosis comes down to clinical judgment.
'We are uncertain of a cause'
Idil Abdull, an autism activist from Burnsville, said the reasons for the soaring numbers are a mystery. "If autism had a middle name, it would be uncertainty," said Abdull, who has a 9-year-old son with autism. "We are uncertain of a cause, a cure ... [and] no two kids have the same symptoms."
But Abdull, who was appointed this week to a federal advisory panel, the Interagency Autism Coordinating Committee, says the report is significant. "Autism is real and it's increasing and I don't think the numbers can be explained by just raising awareness."
Sherrie Kenny, CEO of the Autism Society of Minnesota, said she suspects many autistic children were called something else in the past, such as learning disabled. Now, she said, "the diagnostic tools are by far much better, and we are diagnosing kids earlier and diagnosing them correctly."
But to her, the debate is beside the point. "I'm saying it's here, it's now, we've got to deal with it," she said. "It's not what number's right."
Minnesota was not one of the 14 states studied in the new report, and it does not track autism cases, the Minnesota Department of Health said. But Minnesota schools have reported a huge leap in the number of children classified with autism, from 2,200 in 2000 to 15,400 this year, said the Department of Education, which tracks special education students. During that same period, however, the number of children classified under "specific learning disabilities" dropped by 9,000.
"We're seeing some shifting, absolutely," said Barbara Troolin, director of special education.
At the same time, she said, there are signs that the autism explosion may be leveling off. The Minnesota numbers had been growing by 1 percent a year for most of the past decade but slowed to half a percent in each of the past two years.
The CDC set up a network of surveillance sites nationwide in response to rising concern over skyrocketing diagnosis rates in the 1990s. Researchers do not examine children but instead periodically review records of 8-year-olds.
In its first analysis, using data from 2000, the CDC estimated that 1 in 150 children had some form of the disorder. The latest estimate of 1 in 88 is already being touted as evidence that something in the environment is driving up cases.
"Autism is now officially becoming an epidemic in the United States," said Mark Roithmayr, president of the advocacy group Autism Speaks.
In all, the CDC identified 3,820 children with some form of autism, out of a total of 337,093 studied. As has been previously established, autism is five times more common in boys than girls. The rate was 1 in 54 for boys, and 1 in 252 girls. The rate for whites was 1 in 83, 1 in 127 for Latinos and 1 in 98 for blacks, but the data show those minority groups have been closing the gap.
Staff writer Maura Lerner and the Washington Post contributed to this report.