Approximately 1% of 8-year-old children in the United States meet criteria for an autism spectrum disorder, based on results of a nationwide study of 8-year-olds conducted in 2006. The findings were published in a surveillance summary as part of the Centers for Disease Control and Prevention's Morbidity and Mortality Weekly Report.
“No single factor explains the change in prevalence,” said Catherine Rice, Ph.D., of the National Center on Birth Defects and Developmental Disabilities. Dr. Rice presented the study results in a telebriefing.
The study included health and education records from 11 communities throughout the United States participating in the Autism and Developmental Disabilities Network (ADDM). The project was funded by the CDC. Dr. Rice and her colleagues at the CDC focused on 8-year-olds because most children with autism spectrum disorder (ASD) have been identified by this age. A team of clinicians reviewed the records to confirm ASD diagnoses and identified 2,757 children who met criteria for ASD (MMWR 2009;58[SS-10]:1–24).
The prevalence of ASD among 8-year-olds increased by an average of 57% between 2002 and 2006, based on data from 10 reporting communities that participated in the study in both years. This increase might be attributable to improved diagnostic techniques, but “a true increase in the risk for children to develop ASD symptoms cannot be ruled out,” the researchers said.
Increases in ASD occurred across sex, ethnicity, and cognitive function, but the most consistent pattern was the increase in ASD among boys, Dr. Rice said. Overall, the prevalence of ASD was 1 in 70 boys and 1 in 315 girls, which amounts to a four to five times higher prevalence in boys, compared with girls.
The American Academy of Pediatrics supports ongoing developmental screening for children, Dr. Rice said.
The take-home message for pediatricians from the study is twofold. “Pediatricians should be listening to parents if they have a concern about their child's development, but also proactively following the screening guidelines,” Dr. Rice said. She advised all primary care physicians who suspect ASD in a child to refer the child for further diagnostic evaluation or intervention.
The researchers did not conduct in-person evaluations of each child, and the results were limited by variations in record keeping. The study was not designed to evaluate causes of ASD, but the findings suggest that more research is needed to determine how genetic and environmental factors interact to cause ASD spectrum symptoms, the researchers wrote.
“We will continue our work in tracking trends and our research into potential risk factors so we can understand changes in ASD rates over time,” Dr. Rice said.
“We hope that these new data might raise awareness about ASD to help improve early identification and intervention, and to provide information for policy and service planning,” she added.
For more information about autism and ADDM projects, visit cdc.gov.
FULL TEXT