Rates of Autism With or Without Intellectual Disabilities Related to Sociodemographics

The prevalence of autism spectrum disorder (ASD) with and without intellectual disabilities (IDs) differed on the basis of ethnicity and socioeconomic status, according to results of a study published in Pediatrics.

Investigators from Rutgers School of Public Health in the United States sourced data for this cross-sectional study from the New Jersey Autism Study which was nested within the Autism and Developmental Disabilities Monitoring (ADDM) Network. Children (N=4661) with ASD aged 8 years old living in New Jersey between 2000 and 2016 were evaluated for the presence of ID. Trends in the prevalence in ID were evaluated on the basis of sociodemographic characteristics.

Overall, most children with ASD did not have ID (59%).

Over time, from 2000 to 2016, the prevalence of ASD increased from 9.6 per 1000 to 31.8 per 1000, respectively. Stratified by the presence of ID, ASD with ID (ASD-I) increased from 2.9 per 1000 in 2000 to 7.3 per 1000 in 2016 compared with 3.8 per 1000 to 18.9 per 1000 for ASD without ID (ASD-N), respectively.

Stratified by patient characteristics, ASD-I occurred among more boys than girls (prevalence ratio [PR], 2.1 vs 1.8), Hispanic children compared with Black or White children (PR, 2.8 vs 2.0 vs 1.5), and among children with low or middle socioeconomic status compared with high socioeconomic status (PR, 1.4 vs 1.4 vs 0.7), respectively.

For ASD-N, more girls than boys (PR, 5.8 vs 5.2) and Hispanic children, compared with Black or White Children (PR, 9.3 vs 5.0 vs 4.2), and children with low socioeconomic status compared with middle or high socioeconomic status (PR, 1.9 vs 1.6 vs 1.0) had ASD-N, respectively.

Based on the enhanced ID definition, ASD-I was more common among boys compared with girls (adjusted rate ratio [aRR], 3.9), Black (aRR, 2.1) and Hispanic (aRR, 1.7) children compared with White children, and children born in 2006 (aRR, 1.5) or 2008 (aRR, 1.4) compared with 2002 whereas ASD-N was more common among boys than girls (aRR, 4.4), children with middle (aRR, 2.0) or high (aRR, 1.8) socioeconomic status compared with low socioeconomic status, and children born in 2008 (aRR, 1.8) or 2006 (aRR, 1.6) compared with 2002. Black children were less likely to be diagnosed with ASD-N compared with White children (aRR, 0.7).

Similar trends were observed when using intellectual quotient (IQ) scores to define ID.

This study may have been limited, as 33% of children classified as ASD-N had IQ scores that were borderline.

Study authors concluded, “We observed that 2-in-3 children with ASD do not have cooccurring ID, indicating increased identification of ASD without ID among all demographic subgroups from 2000 to 2016. However, our findings underscore the likely presence of health disparities in ASD without ID identification, especially among disadvantaged children.”