Feb. 8, 2007 -- Autism disorders are "more common than previously believed," affecting about one in 150 8-year-olds in the 14 states studied, says the CDC.
That's higher than previous CDC estimates of up to one in 166 children.
Autism spectrum disorders (ASDs) include autistic disorder, Asperger's syndrome, and pervasive developmental disorder (including atypical autism). These disorders involve impairments with social, communicative, and behavioral skills.
CDC officials pointed out that the new figures don't represent all U.S. children, or show whether autism is increasing in the U.S.
But the CDC's study was designed to provide "more consistent and reliable estimates," says the CDC's Marshalynn Yeargin-Allsopp, MD.
"Our estimates are becoming better and more consistent, though we can't yet tell if there is a true increase in ASDs or if the changes are the result of our better studies," says CDC director Julie Gerberding, MD, MPH, in a CDC news release.
"We do know, however, that these disorders are affecting too many children," Gerberding says.
Autism spectrum disorders are an "urgent public health issue that affects the lives of many families and communities," Yeargin-Allsopp told reporters.
Yeargin-Allsopp heads the Developmental Disabilities branch of the National Center on Birth Defects and Developmental Disabilities.
The CDC report calls for greater efforts to diagnose children as early as possible so they can be treated -- and shows that early diagnosis is too rare.
It appears in the CDC's Morbidity and Mortality Weekly Report Surveillance Summaries.
The report tracks the prevalence (number of cases) of autism spectrum disorder cases in 407,578 children in 14 U.S. communities who were 8 years old in 2002.
The communities are in Alabama, Arizona, Arkansas, Colorado, Georgia, Maryland, Missouri, New Jersey, North Carolina, Pennsylvania, South Carolina, Utah, West Virginia, and Wisconsin.
The study identified 2,685 children in those communities as having an autism spectrum disorder.
Those children's school or health care records either showed an autism spectrum disorder diagnosis or "unusual social behaviors consistent with an ASD [autism spectrum disorder]," the CDC report says.
The average ASD prevalence among the 14 study sites was 6.6 per 10,000 children, or about one in 152 children.
New Jersey had the highest ASD prevalence rate of the 14 sites: 10.6 per 1,000 8-year-olds -- or one in 94 children.
The Alabama site had the lowest rate: 3.3 per 1,000 8-year-old children, or one in 303.
The remaining 12 sites had prevalence rates ranging from 5.2 to 7.6 per 1,000 8-year-olds.
The report also tracked ASD prevalence rates from 2000 to 2002 in six of the states -- Arizona, Georgia, Maryland, New Jersey, South Carolina, and West Virginia.
During that time, disease prevalence was stable in four of the states, but rose 17% in Georgia and 39% in West Virginia.
"While the stability of ASD's in four of the six sites is encouraging, the increase in two sites is a concern," says CDC behavioral scientist Catherine Rice, PhD.
"We cannot make conclusions about trends in ASD prevalence at this time," she says. "However, continued monitoring of ASD prevalence in these sites will help us answer that question starting with children born in the 1990s."
Increase in Autism?
"For decades, autism was believed to occur in four to five per 10,000 children," Yeargin-Allsopp told reporters.
"Studies done in more recent times have been summarized as ASD occurring in two to six per 1,000 children. As a general statement, we have used the figure of up to 1 in 166 children have an ASD, based on recent studies done in multiple countries," she says.
"It is extremely difficult to accurately estimate the number of children who have an ASD," Yeargin-Allsopp says in a CDC news release.
"Medical records often do not provide such information, and identification is often made by schools or education specialists," says Yeargin-Allsopp.
"Because autism is a behavioral condition, children are often diagnosed at different ages, and many are not diagnosed until they enter school," she says.
Goal: Earlier Diagnosis
Delays in diagnosing the disorders is one of the CDC's concerns.
Rice notes that most children identified with an autism spectrum disorder "had documented concerns by a parent or professional before three years of age, such as concerns about the child's language, social, or play development.
"But the median age of earliest ASD diagnosis was approximately 4.5 to 5.5 years," says Rice.
The earlier children are diagnosed with autism spectrum disorders, the sooner treatment can start.
Due to the benefits of early intervention, it's "essential to ensure that children receive optimal early intervention services," states the report.
Experienced doctors using standardized methods "can reliably diagnose autism" in children as young as 2 years old, the report says.
The report tracks statistics. It doesn't address ASD causes or reasons for geographical patterns in prevalence.
"We hope this information ... will be part of the larger public and private effort to understand the impact of ASDs, the causes of the disorders, and the most effective interventions to provide in order to help each individual reach their full potential," Rice says.