About one in 150 children has a developmental disability classified as an autism spectrum disorder (ASD), a new study shows.
Surveillance teams, including a group at the School of Medicine, used health records and school data to analyze autism prevalence among children born in 1992 and 1994 in 14 different regions around the nation.
The study was produced by the Autism and Developmental Disabilities Monitoring Network (ADDM), a multiple-state surveillance project funded by Centers for Disease Control and Prevention (CDC). To gather data for the St. Louis area, epidemiologists reviewed data on children born in 1994 in St. Louis city and St. Louis, Franklin, Jefferson and St. Charles counties.
The study, which appeared in a recent issue of the CDC’s Morbidity and Morality Weekly Report Surveillance Summaries, also includes data from Alabama, Arizona, Arkansas, Colorado, Georgia, Maryland, New Jersey, North Carolina, Pennsylvania, South Carolina, Utah, West Virginia and Wisconsin.
Among metropolitan St. Louis children, ASD prevalence was 7.3 per 1,000. Other sites reported ASD prevalence estimates ranging from a low of 3.3 per 1,000 in Alabama to a high of 10.6 per 1,000 in New Jersey. The overall prevalence estimate using data from all 14 ADDM sites was 6.6 per 1,000. ASD rates were 3.6 times higher among St. Louis-area boys than among girls.
Scientists stressed that the results cannot be used to determine if the popular perception that autism has sharply increased in recent decades is true.
“Given the changes in reporting and diagnostic criteria for autism over the past 10-20 years, we cannot provide a definitive answer to that question,” said Edwin Trevathan, M.D., professor of neurology and of pediatrics and Missouri ADDM principal investigator. “But these new data provide us a comparative baseline we can use as we watch for changes in prevalence in the future. Increases in prevalence in specific locations will then be carefully investigated.”
The ADDM sites assessed the medical records of about 594,000 children, identifying nearly 4,000 children with an ASD. The data represent the largest prevalence study of autism ever done in the United States to date, but they cannot be used to estimate prevalence of autism in areas not participating in the ADDM network. The investigators hope that their data will help ADDM communities estimate how many children may develop ASDs and plan accordingly for assistance and treatment.
Little is known of the causes of ASDs, but research has shown that earlier diagnosis can maximize the effects of available treatments. Data from this study showed that the median age for diagnosis with an ASD typically fell somewhere in a child’s fourth year, but previous research has shown that diagnosis often is possible when a child is as young as 18 months. Public health officials are hoping to push physicians to make earlier diagnoses through increased awareness and improved diagnostic techniques.
“It is important for parents, health-care professionals and childcare providers to recognize developmental milestones such as smiling, pointing and waving bye-bye,” said Marshalyn Yeargin-Allsopp, M.D., chief of the CDC’s autism program. “I encourage all health-care professionals to give children routine developmental and autism-specific screenings.”