Autism Spectrum Disorders in Preschool-Aged Children: Prevalence and Comparison to a School-Aged Population

Purpose

The purpose of this study was to determine the prevalence and case characteristics of children with autism spectrum disorders (ASDs) among 4-year-olds and to compare findings to previous prevalence estimates for 8-year-olds in the same geographic area.

Methods

South Carolina (SC) has been a participant in the Centers for Disease Control and Prevention's active, population-based, multiple-site ASD surveillance network for 8-year-olds since 2000. The 8-year-old methodology, designed to identify children both with and without prior diagnosis, was applied in SC with modification to include information sources for younger children.

Results

The ASD prevalence among 4-year-olds in 2006 was 8.0 per 1000 (95% confidence interval [CI], 6.1–9.9), or 1 in 125. In comparison, ASD prevalence among 8-year-olds in the same geographic area was 7.6 (95% CI, 5.7–9.5) in 2000 and 7.0 (95% CI 5.1–8.9) in 2002. Developmental concerns were documented at earlier ages across time, and while most cases received services, only 20% to 29% received services specific to ASD.

Conclusions

Findings should provide useful information for the planning of health/education policies and early intervention strategies for ASD.

Key Words: Autism, Developmental Disabilities, Public Health Surveillance

Selected Abbreviations and Acronyms: ASD, autism spectrum disorder, CDC, Centers for Disease Control and Prevention, ADDM, Autism Developmental Disabilities and Monitoring (Network), SC, South Carolina, DDSN, Department of Disabilities and Special Needs, DHEC, Department of Health and Environmental Control, DSM-IV-TR, Diagnostic and Statistical Manual of Mental Disorder, Fourth Edition, Text Revision, PDD-NOS, Pervasive Developmental Disorder–Not Otherwise Specified, CI, confidence interval, ICD-9, International Classification of Diseases, Ninth Revision, AAP, American Academy of Pediatrics, SD, standard deviation