A new survey of parents suggests that as many as one out of every 45 U.S. children aged between 3 and 17 years have autism, a number that far exceeds official U.S. estimates of one in 68 children, U.S. researchers said on Friday.
The new parent survey results reflect a nearly doubling in autism rates over the last three years, but researchers at the U.S. Centers for Disease Control and Prevention, which released the data, say the shift is largely due to a change in the way the survey questions were worded.
The new numbers, which are based solely on a parent survey, do not replace CDC's official autism estimate of one in 68, which is based on more extensive research than parental surveys, agency researchers said.
For its survey, the CDC's National Center for Health Statistics contacted 43,283 parents using a new set of survey questions that included more specific diagnostic terms. Those changes may have caused more parents to say that their child had been diagnosed with autism or other developmental disabilities.
For example, the new survey included the names of specific diagnoses within the autism spectrum such as Asperger s and pervasive developmental disorder, categories that were "intended to help cue recall of past diagnoses," the CDC said.
CDC epidemiologist Benjamin Zablotsky told Reuters the new questions improved the accuracy of the survey, and did not reflect a surge in prevalence of autism in the United States.
"We obviously can't rule out entirely that there could be a true increase," Zablotsky said. "But that is something that would require really dramatic and rapid changes to the risk factors involved, and that seems unlikely."
In the survey, parents were asked whether they had ever been told by a doctor that their child had an intellectual disability, autism or another developmental delay. The prevalence of autism soared in the new survey, while parents reported far fewer cases of other developmental delays.
The combined total of autism cases and other developmental delays, however, was unchanged, suggesting that rewording the question helped parents answer more accurately, Zablotsky said,.
Michael Rosanoff of the advocacy group Autism Speaks said the one in 45 estimate is "not surprising" and is likely a more accurate representation of autism prevalence in the United States. The group has long suggested that U.S. officials have been underestimating the commonness of the condition.
Wendy Fournier, president of the National Autism Foundation and the mother of a 15-year-old child with the condition, said the results released on Friday offer "newer information that we feel better reflects the current prevalence of autism."