Prevalence of Autism Spectrum Disorders In Hispanic and Non-Hispanic White Children

Background: Although the number of individuals diagnosed with autism spectrum disorders (ASD) has risen substantially over the last decade or more, most prevalence estimates indicate that ASD is being diagnosed less commonly in Hispanic individuals, compared to the non-Hispanic White population. 

Objectives: The purpose of this report is to analyze differences in ASD prevalence between Hispanic and non-Hispanic White 8-year-old children in the Arizona Developmental Disabilities Surveillance Program (ADDSP), and to explore how prevalence has changed over time in these ethnic groups. 

Methods: The ADDSP is a population-based surveillance system for ASD in Maricopa County, Arizona. The ADDSP has been conducted as part of the Autism and Developmental Disabilities Monitoring Network (ADDM), funded by the Centers for Disease Control and Prevention at multiple sites across the United States.  The ADDM surveillance system ascertained ASD among 8 year-old children in years 2000, 2002, 2004, and 2006. Data are obtained via systematic review of clinical and educational records, which are evaluated by trained clinician reviewers to determine whether children meet ADDM criteria for ASD. 

Results: In all study years, both non-Hispanic White (p < .005) and Hispanic (p < .05) samples included significantly more males than females who met ASD case definition. Across all study years, significantly more Hispanic children carried a Special Education Exceptionality of Intellectual Disability when compared to non-Hispanic White children (p < .05). In each study year, ASD prevalence in non-Hispanic White children was significantly higher than Hispanic children (p < .005). Estimation of regression lines representing change in prevalence over time showed that the prevalence of ASD significantly increased over time for Hispanic males, for whom prevalence increased from 3.4 per 1000 children in 2000 to 11.4 in 2006 (β = 2.94, p = .04). Non-Hispanic White male prevalence showed a trend toward significant increase, from 13.6 per 1000 children in 2000 to 23.6 in 2006 (β = 3.80, p = .08). Similarly, Hispanic females showed a trend toward significant increase, from 2.0 per 1000 children in 2000 to 4.1 in 2006 (β = 0.79, p = .06). Non-Hispanic White female prevalence did not change significantly over time (β = 0.74, p = .29). Slopes of the regression lines were compared to determine if prevalence increased at different rates depending on ethnicity and gender. Boys experienced significantly faster increases in prevalence over time compared to girls (p = .005), but comparisons of slopes across ethnicity were not significant. 

Conclusions: These results support recent reports of increasing prevalence of ASD in many regions of the United States. In keeping with findings of recent literature, results of the current study indicate that Hispanic children have lower ASD prevalence as compared to non-Hispanic Whites. Of particular importance is the markedly higher ASD prevalence for Hispanics in this sample compared to results of previous investigations. Building on existing ASD prevalence literature which has largely examined single point-in-time prevalence, results of the current study show that ASD prevalence in non-Hispanic White and Hispanic males is rising significantly faster than in females.