Autism and related developmental 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 School of Public Health and the Centers for Disease Control and Prevention.
The study, a partnership between the university, the CDC and 10 other U.S. research sites, shows that one in 110 American 8-year-olds is classified as having an autism spectrum disorder -- a 57 percent increase in cases as compared to four years earlier.
The new findings, just published in the CDC's "Morbidity and Mortality Weekly Report," highlight the need for social and educational services to assist those affected by the condition, said Beverly Mulvihill, associate professor of public health at Alabama and co-author of the study.
Autism spectrum disorders are a group of developmental disabilities characterized by delays or changes in childhood socialization, communication and behavior.
The study discusses possible factors that might contribute to the increase in autism diagnoses. They include a broader definition of disorders, as well as a heightened awareness of conditions by parents, doctors, educators and other professionals.
The findings do not address whether or not the increase is attributable to a true rise in the risk of developing autism, or if they are related to more frequent and earlier diagnoses, or other factors, like environmental.
Data comes from the Autism and Developmental Disabilities Monitoring Network, a collection of sites in Alabama, Arizona, Colorado, Florida, Georgia, Maryland, Missouri, North Carolina, Pennsylvania, South Carolina and Wisconsin. Reviewers there are uniformly trained to analyze and confirm cases; some children included in the study have documented symptoms, but have never received a diagnosis.
The study also found that boys are 4.5 times more likely than girls to have autism, a finding that confirms earlier studies, according to Martha Wingate, assistant professor of public health at Alabama and study co-author.
The sites are not selected on any statistical pattern, but the 300,000-plus children included in the study represent 8 percent of the nation's 8-year-olds.