Socioeconomic disparity in the prevalence of autism spectrum disorder in Wisconsin.

BACKGROUND The number of children receiving services for autism spectrum disorders in Wisconsin and nationally has steadily increased in recent years. The Wisconsin Surveillance of Autism and Other Developmental Disabilities System was developed to study the prevalence of and risk factors for autism spectrum disorders. This analysis of Wisconsin surveillance data examined whether autism prevalence is positively associated with socioeconomic status. METHODS Surveillance methods developed by the Centers for Disease Control and Prevention were used to determine the number of 8-year-old children with an autism spectrum disorder in a 10-county area of southeastern Wisconsin in 2002. Socioeconomic status quintiles were created based on census block group indicators. Autism prevalence was computed for each socioeconomic status quintile of the population. RESULTS Using educational attainment as an indicator of socioeconomic status, autism spectrum disorder prevalence increased from 2.6 per 1000 in the lowest to 6.8 per 1000 in the highest education quintile. The prevalence ratio for the highest to lowest education quintile was 2.6:1 (95% confidence interval: 1.6, 4.5). Using median household income as an indicator of socioeconomic status produced similar results. CONCLUSION Autism spectrum disorder prevalence is positively associated with socioeconomic status based on population-based surveillance in Wisconsin.