The number of children with autism is "significantly" higher than previously thought, according to a new report released by the Centers for Disease Control and Prevention.
School-aged boys were four times more likely to have an autism spectrum disorder (ASD) diagnosis than girls, according to the new data.
The CDC released a report a year ago estimating 1 in 88 American children has a form of autism spectrum disorder - neurodevelopmental disorders that lead to impaired language, communication and social skills. The report looked at medical and educational records of all 8-year-olds living in 14 areas of the United States during 2008.
This new report is drawn from answers given by parents of children between the ages of 6 and 17 in a telephone survey. Based on the answers provided by parents who chose to answer questions, the survey suggests that 1 in 50 school-aged children have autism.
The CDC's National Center for Health Statistics conducted the survey between February 2011 and June 2012. When the topic of autism was raised, the family member was asked if they had ever been told by a doctor or other health care provider that their child had any form of autism. If the answer was yes, they were asked if the child currently had autism. If the answer to that question was also yes, then the parent or guardian was asked if the autism diagnosis was "mild," "moderate" or "severe."
"The new data does suggest that the number of children with autism is higher than we had estimated four years ago. This will have implications for health care providers and school systems," says Stephen Blumberg, a health scientist with CDC?s National Center for Health Statistics and lead author of the research published online Wednesday.
When this survey was conducted in 2007, 1.6% of parent said they had a child with an autism diagnosis -- which suggests 1 in 86 school-age children have some form of autism. In this latest study, 2% of parents said their child currently had a diagnosis of some for of autism.
Based on this new CDC report and last year's CDC report, "it's really tough to know what the true prevalence of ASD is," says Zachary Warren, director of Vanderbilt University's Treatment and Research Institute for Autism Spectrum Disorders.
"One estimate is based on parent reporting, one is based on record (medical and educational) reviews -- neither of those estimates include direct observations of children."
Blumberg says he can't say which prevalence study is more accurate because they are two different types of studies, looking at two different things (medical/educational records of 8-year-olds vs. parents of school-age children reporting on their child's diagnosis).
However, both sets of data show "increases in the prevalence of autism over time," Blumberg says.
Only 23% of those surveyed participated in the survey. That's down from a 47% response rate in 2007. The CDC insists that "although the potential for bias cannot be ruled out, differences between respondents and non-respondents should not have a major impact on the conclusions of this report."
Not everyone agrees with this assessment. "If your child has a problem, you're more likely to respond ... that's just common sense," says Dr. Max Wiznitzer, a neurologist and autism expert at Rainbow Babies and Children's Hospital in Cleveland, Ohio.
"I am concerned that this report will be interpreted as a true rise in the prevalence of autism, when all we're talking about is a label that has been given at some time in a child's life, with no knowledge of who gave the label, their experience in assessing children with autism and the reason for the label," says Wiznitzer.
The advocacy group Autism Speaks believes this latest CDC report provides growing evidence that the number of children with autism spectrum disorders is underestimated in the United states, says Michael Rosanoff, associate director for public health research and scientific review for the organization.
Experts agree that the earlier a child is diagnosed with autism, the better the chances are for a child to overcome the difficulties that come with the disorder. Rosanoff notes that "the majority of new autism diagnoses is in children 7 years or older who never had a diagnosis."
And even though many of these new cases of autism were mild forms of the disorder, he says even mildly affected children who are in regular school settings can struggle and may be in need of services to help them cope with autism spectrum disorder. "We need to have more research funding to understand why the prevalence is so high," he says.
Warren says there is no doubt that the field of autism is simultaneously struggling with problems of over-identification and under-identification of these disorders. "We need to find a way to standardize identification of children with autism and then translating it into effective treatment."