Prevalence and characteristics of children with autism-spectrum disorders

Abstract

Purpose: The purpose of this study was to determine the prevalence of autism spectrum disorders (ASD) and associated characteristics among 8-year-old children.

Methods: This is an ongoing active, population-based surveillance program conducted in South Carolina as part of the Centers for Disease Control and Prevention's Autism and Developmental Disabilities Monitoring Network. Cases from the state's first two study years (2000 and 2002) have been combined for analysis, resulting in surveillance of 47,726 children who are 8 years of age.

Results: A total of 295 children met criteria for ASD, yielding a prevalence of 6.2 per 1000. The racial distribution of cases was similar to that of 8-year-old children in the study area, with boys more commonly affected than girls (3.1:1). Seventy-nine percent of cases were served in special education, 36% of these under Autism classification. Analyses by gender showed differences in diagnostic criteria and intellectual functioning. Girls more often were cognitively impaired (IQ <or= 70) than boys (72.7% vs. 56.4%), although among those most severely impaired (IQ <or= 34), boys and girls were equally represented.

Conclusions: Results indicate that ASDs affect 1 in 162 children 8 years of age in South Carolina. Continuing surveillance will permit assessment of potential changes in this prevalence estimate over time.