Autism and related development disorders are becoming more common, with a prevalence rate approaching 1 percent among American 8-year-olds, according to new data from researchers at the University of Alabama at Birmingham (UAB) School of Public Health and the Centers for Disease Control and Prevention (CDC).
The study is a partnership between UAB, the CDC and 10 other U.S. research sites. It shows that one in 110 American 8-year-olds is classified as having an autism spectrum disorder (ASD), a 57 percent increase in ASD cases compared to four years earlier.
The new findings, published Dec. 18 in the CDC's Morbidity and Mortality Weekly Report (MMWR), highlight the need for social and educational services to help those affected by the condition, said Beverly Mulvihill, Ph.D., a UAB associate professor of public health and co-author on the study.
ASDs are a group of developmental disabilities such as autism and Asperger disorder that are characterized by delays or changes in childhood socialization, communication and behavior.
"This is a dramatic increase in the number of kids classified as autistic or documented on the spectrum of similar disorders," Mulvihill said. "It is not entirely clear what is causing the rise, but we know major collaborative efforts are needed to improve the understanding and lives of people and families impacted."
The MMWR study discusses possible factors that might contribute to the increase in ASD cases. They include a broader definition of autism disorders and a heightened awareness of ASD by parents, doctors, educators and other professionals. The findings do not address whether or not any of the increase is attributable to a true increase in the risk of developing ASD, more frequent and earlier diagnoses, and other factors.
Data comes from the Autism and Developmental Disabilities Monitoring (ADDM) Network, a collection of 11 sites in Alabama, Arizona, Colorado, Florida, Georgia, Maryland, Missouri, North Carolina, Pennsylvania, South Carolina and Wisconsin. ADDM reviewers are uniformly trained to review and confirm cases; some children included in the study have documented ASD symptoms but never received a diagnosis.
The study also found that boys are 4.5 times more likely than girls to have ASD, a finding that confirms earlier studies, says Martha Wingate, Dr.P.H., a UAB assistant professor of public health and study co-author.
"It still is not clear why males more frequently are affected," Wingate said. "One thing we know for sure is that more research is needed to quantify the effects of single or multiple factors such as diagnosis patterns, inclusion of milder cases and other components."
The ADDM sites are not selected based on any statistical pattern, but the 300,000-plus children included in the study represent 8 percent of the nation's 8-year-olds.