May 4, 2006
US Survey Shows Autism Very Common
By Maggie Fox, Health and Science Correspondent
WASHINGTON (Reuters) - The first national surveys of autism show the condition is very common among U.S. children -- with up to one in every 175 with the disorder, the U.S. Centers for Disease Control and Prevention said on Thursday.
This adds up to at least 300,000 U.S. schoolchildren with autism, a condition that causes trouble with learning, socializing and behavior, the CDC said.
The CDC analyzed data on 24,673 children whose parents took part in two separate government surveys on health in the United States to generate its first national estimate of the prevalence of autism.
"Together, these two national surveys of parents indicate that at least 300,000 children aged 4 to 17 years old had autism in 2003-04," the CDC said in the report.
The surveys came up with similar results -- that autism has been diagnosed in anywhere between 5.5 per 1,000 and 5.7 per 1,000 children aged 4 to 17. This translates to between one in every 175 to one in every 181 children.
"(The surveys) affirm that autism is a condition of major public health concern that affects many families," Dr. Jose Cordero, director of CDC's National Center on Birth Defects and Developmental Disabilities, told reporters in a telephone briefing.
He said the findings fit in with previous estimates of autism, which were based on local surveys done in Atlanta and New Jersey.
The 1996 Metropolitan Atlanta Developmental Disabilities Surveillance Program survey showed autism had been diagnosed in 3.4 per 1,000 of the 3- to 10-year-olds included, or one in every 296. The 1998 Brick Township, New Jersey survey showed a rate of 6.7 per 1,000 children of the same age, or one in every 166.
None of the surveys pointed to a cause for autism -- a matter of deep controversy in the United States. Some groups have accused the CDC of covering up data that would link autism with vaccines, although studies in several countries have discounted such a link.
"We recognize that parents want answers," Cordero said.
"If children have autism, parents want to know what caused it and how they can lower this risk if they have other children. We share their frustration."
While there were some differences among age groups, the CDC said the differences were not statistically significant.
"Both surveys indicated that boys were nearly four times more likely to have been diagnosed with autism than girls," the CDC said in the report, published in its weekly report on death and disease.
"Both surveys indicated that Hispanic children were less likely to have an autism diagnosis." The survey could not indicate why that might be.
Laura Schieve, an epidemiologist at the National Center on Birth Defects and Developmental Disabilities who helped conduct the study, said the study could not answer many questions about autism.
"Although often autism can be identified as early as 18 months, many children will not be diagnosed until they get to school," she told the briefing.
And parents of older children could easily have forgotten an early childhood diagnosis, she said.
"After children have received treatment for an extended time, they may show fewer symptoms of autism," she added.
"Also the criteria for autism have been broadened slightly."