Features of Autism Spectrum Disorders Vary by Race and Ethnicity

Background: One of the most challenging aspects in diagnosing Autism Spectrum Disorders (ASD) is the wide heterogeneity of features in individual children. Some features such as inattention/hyperactivity or intellectual disability that are associated with the ASDs are not included in current diagnostic algorithms. These ASD-associated features (AAF) are rarely studied and their distribution in ASD cases is therefore poorly understood. These features may differ across characteristics such as race/ethnicity, socioeconomic status, gender, or cognitive functioning. Examining the distribution of AAF associated with ASD among racial/ethnic groups may further our understanding of the differences among children with ASD and improve community identification of this disorder. Objectives: To examine differences in ASD associated features according to racial/ethnic sub-populations using a population-based surveillance system. Methods: Utilizing data from the Autism and Developmental Disabilities Monitoring (ADDM) network, we analyzed AAF among 4325 eight-year-old children, born between 1992 and 1998, who met the ASD case definition used by the ADDM network. Outcomes included 12 documented AAF, including behavioral, mood, and developmental characteristics. Race/ethnicity was the independent variable of interest. We analyzed data using logistic regression stratified by level of cognitive functioning to determine whether race/ethnicity predicted the presence of each of the 12 AAF. Results: Of the 4325 ASD children, 81.5% were male, 57.6% were White non-Hispanic, 23.2% were Black non Hispanic, and 9.9% were Hispanic. Additionally, 43.1% had IQs >70, 31.3% had IQs ≤ 70 and 25.7% were missing IQ scores in their records. Data on AAF were > 98% complete except for abnormalities in eating/drinking/sleeping (EDS) which rate is lower. For IQ > 70: compared to non-Hispanic White (NHW), Black non-Hispanic children had a significantly higher occurrence of six of twelve AAF: 1) abnormalities in EDS; 2) argumentative, oppositional, defiant, destructive features; 3) delayed motor milestones; 4) odd responses to sensory stimuli; 5) self-injurious behavior; and 6) temper tantrums. However, they had a significantly lower occurrence in two AAF: 1) uneven cognitive development or cognitive scatter; and 2) staring spells and seizure-like activity. Hispanic children were significantly more likely than NHW children to have an increase in odd sensory responses. For children with IQ ≤ 70, Black non-Hispanic, compared to NHW, had a significantly higher rate of: 1) abnormalities in EDS; 2) delayed motor milestones; and 3) odd responses to sensory stimuli. Compared to NHW children, Hispanic children had a greater occurrence of: 1) abnormalities in EDS; 2) uneven cognitive development or cognitive scatter; 3) aggression; 4) odd responses to sensory stimuli; and 5) self-injurious behavior. Conclusions: These preliminary analyses indicate that distribution of AAF varies by race/ethnicity, depending upon level of cognitive functioning (i.e. IQ). However, certain AAF were more common among both minority groups compared to NHW children regardless of IQ level: abnormalities in EDS, delayed motor milestones, and odd responses to sensory stimuli. Inclusion of other factors, such as SES, and timing of ASD diagnosis is needed for further analysis.