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," said Levy. "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 put the number at 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 other government estimate has not been formally released yet. But because of the new published findings, officials from the Centers for Disease Control and Prevention decided to announce Friday during an embargoed press briefing that their preliminary findings also show about 1 in 100 children have the disorders.
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Dr Aaron's Comments
In the 1980s the rate of autism was 1 in 10,000. Now just 20 years later we are at a rate of 1 in 91. The numbers are even higher when you look at boys alone. Many people have felt that it was the mercury in vaccines that have been the cause. Since taking the mercury out of most childhood vaccines the rate has continued to increase. While mercury could and probably has played a part we can see that there are other factors at play. More and more research is coming out showing that chemicals in our environment are the cause., especially inutero exposure to everyday chemicals. Another area of potential exposure is still vaccines. Either from the chemicals still be added or from the actual viruses found in the vaccine. On May 18th we will be having a seminar on vaccines to help people become more informed. Look for more details to come on this very informative seminar.