Summary: Between 2000 and 2016, documented cases of ASD increased as much as 500% in the New York – New Jersey metro region. The highest increase was in children without intellectual disabilities. Researchers say as many as 2 out of 3 children diagnosed with autism have no intellectual disabilities at all.
Source: Rutgers University
Documented cases of autism spectrum disorder (ASD) in the New York–New Jersey metro region increased by as much as 500 percent between 2000 and 2016, with the highest increase among children without intellectual disabilities, according to a Rutgers study.
This is the opposite of past findings, which have suggested that autism typically co-occurs with intellectual impairment.
“One of the assumptions about ASD is that it occurs alongside intellectual disabilities,” said Josephine Shenouda, an adjunct professor at the Rutgers School of Public Health and lead author of the study published in the journal Pediatrics.
“This claim was supported by older studies suggesting that up to 75 percent of children with autism also have intellectual disability.”
“What our paper shows is that this assumption is not true,” Shenouda said. “In fact, in this study, two-in-three children with autism had no intellectual disability whatsoever.”
Using biannual data from the New Jersey Autism Study, researchers identified 4,661 8-year-olds with ASD in four New Jersey counties (Essex, Hudson, Ocean and Union) during the study period. Of these, 1,505 (32.3 percent) had an intellectual disability; 2,764 (59.3 percent) did not.
Subsequent analysis found that rates of ASD co-occurring with intellectual disability increased two-fold between 2000 and 2016 – from 2.9 per 1,000 to 7.3 per 1,000. Rates of ASD with no intellectual disability jumped five-fold, from 3.8 per 1,000 to 18.9 per 1,000.
Shenouda said there may be explanations for the observed increases, though more research is needed to specify the precise causes.
“Better awareness of and testing for ASD does play a role,” said Walter Zahorodny, associate professor at the Rutgers New Jersey Medical School and senior author on the study.
“But the fact that we saw a 500 percent increase in autism among kids without any intellectual disabilities – children we know are falling through the cracks – suggests that something else is also driving the surge.”
ASD prevalence has been shown to be associated with race and socioeconomic status. The Rutgers study identified that Black children with ASD and no intellectual disabilities were 30 percent less likely to be identified compared with White children, while kids living in affluent areas were 80 percent more likely to be identified with ASD and no intellectual disabilities compared with children in underserved areas.
Using New Jersey Autism Study data and U.S. census data, the researchers were able to estimate rates of ASD undercounting in the four counties.
Shenouda said that addressing the findings could help close identification gaps and eventually bring much-needed ASD services to lower-income areas.
“With up to 72 percent of the ASD population having borderline or average intellectual ability, emphasis should be placed on early screening, early identification and early intervention,” she said.
“Because gains in intellectual functioning are proportionate with intense intervention at younger ages, it’s essential that universal screening is in place, especially in underserved communities.
Prevalence and Disparities in the Detection of Autism Without Intellectual Disability
Intellectual ability predicts functional outcomes for children with autism spectrum disorder (ASD). It is essential to classify ASD children with and without intellectual disability (ID) to aid etiological research, provide services, and inform evidence-based educational and health planning.
Using a cross-sectional study design, data from 2000 to 2016 active ASD surveillance among 8-year-olds residing in the New York-New Jersey Metropolitan Area were analyzed to determine ASD prevalence with and without ID. Multivariable Poisson regression models were used to identify trends for ASD with ID (ASD-I) and without ID (ASD-N).
Overall, 4661 8-year-olds were identified with ASD. Those that were ASI-I were 1505 (32.3%) and 2764 (59.3%) were ASD-N. Males were 3794 (81.4%), 946 (20.3%) were non-Hispanic Black (Black), 1230 (26.4%) were Hispanic, and 2114 (45.4%) were non-Hispanic white (white). We observed 2-fold and 5-fold increases in the prevalence of ASD-I and ASD-N, respectively, from 2000-2016. Black children were 30% less likely to be identified with ASD-N compared with white children. Children residing in affluent areas were 80% more likely to be identified with ASD-N compared with children in underserved areas. A greater proportion of children with ASD-I resided in vulnerable areas compared with children with ASD-N. Males had higher prevalence compared with females regardless of ID status; however, male-to-female ratios were slightly lower among ASD-I compared with ASD-N cases.
One-in-3 children with ASD had ID. Disparities in the identification of ASD without ID were observed among Black and Hispanic children as well as among children residing in underserved areas.