April 6, 2023 at 3:33 p.m.
Autism rates march ever higher in new CDC report
2.8 percent of 8-year-olds had ASD in 2020
The new prevalence rate reflects an astonishing 320% increase in the disorder since 2000, when 1 in 150 8-year-olds were diagnosed with ASD. That number climbed to 1 in 88 by 2008, and to 1 in 59 in 2014.
The numbers come from the agency's Autism and Developmental Disabilities Monitoring (ADDM) sites in Wisconsin, Maryland, Arizona, Arkansas, California, Georgia, Minnesota, Missouri, New Jersey, Tennessee, and Utah. The study was published in the March 23, 2023, Morbidity and Mortality Weekly Report.
Autism spectrum disorder (ASD) is a developmental disorder that can be characterized by social and communication challenges, along with limited interests and repetitive behaviors. The prevalence rates in the report were based exclusively on documented ASD diagnostic statements, documented ASD special education classifications, or documented ASD ICD medical codes.
"Of the 6,245 children who met the ASD case definition, 74.7% had a documented diagnostic statement of ASD, 65.2% had a documented ASD special education classification, 71.6% had a documented ASD ICD code, and 37.4% had all three types of ASD indicators," the CDC stated. "The median age of earliest known ASD diagnosis was 49 months and ranged from 36 months in California to 59 months in Minnesota."
As has been the case from the outset of autism record-keeping, boys were nearly four times as likely to be identified with ASD as girls among 8-year-olds. Specifically, ASD was more prevalent in boys than girls by 3.8 times.
However, the percentage of 8-year-old girls with ASD is now more than 1%, the CDC reported, and to researchers that represents a significant marker.
"The new report showing a prevalence greater than 1% in girls is particularly notable because people often think autism spectrum disorder occurs mainly in boys," said Dr. Christine Ladd-Acosta, an associate professor in the Bloomberg School's Department of Epidemiology, and one of two ADDM Network site principal investigators at the Bloomberg School's Wendy Klag Center. "This report highlights that a large number of girls have autism spectrum disorder, too."
There were departures in the statistics this year, too, the CDC reported.
"For the first time, the ADDM Network found that the percentage of 8-year-old Black, Hispanic, and Asian or Pacific Islander children identified with ASD was higher than among 8-year-old white children, which was the opposite of previously observed racial and ethnic differences across the ADDM Network," the CDC report stated.
Specifically, ASD prevalence was lower among non-Hispanic white children (24.3) and children of two or more races (22.9) than among non-Hispanic black or African American (Black), Hispanic, and non-Hispanic Asian or Pacific Islander (A/PI) children (29.3, 31.6, and 33.4 respectively).
"ASD prevalence among non-Hispanic American Indian or Alaska Native (AI/AN) children (26.5) was similar to that of other racial and ethnic groups," the report stated. "ASD prevalence was associated with lower household income at three sites, with no association at the other sites."
According to researchers at the Johns Hopkins Bloomberg School of Public Health, in earlier surveillance efforts beginning in 2000, white 8-year-olds were the most likely to be identified with ASD. Gaps began to narrow in 2014 among 8-year-olds, the researchers found, and by 2018 there were no longer significant differences between the rates of Black and white children being identified as having ASD at all U.S. sites.
The CDC also observed that, among 8-year-old children with ASD, more than one third, or 37.9%, also had an intellectual disability (ID). Intellectual disability (ID) is often seen in children with ASD and can indicate a type of impairment in intellectual ability.
"Intellectual disability was present among 50.8% of Black, 41.5% of A/PI, 37.8% of two or more races, 34.9 percent of Hispanic, 34.8% of AI/AN, and 31.8% of white children with ASD," the CDC stated. "Overall, children with intellectual disability had earlier median ages of ASD diagnosis (43 months) than those without intellectual disability (53 months)."
The group SafeMinds said those IQ numbers knocked down a mainstream contention.
"Data extrapolated from this ADDM report shows that 8-year-olds with an IQ <70 are the most rapidly rising cohort," the group said in a statement. "This group now equals the higher IQ group (85+). When combining the two lower IQ groups (70-85 and <70), an accelerated increase is observed, dispelling the notion that the driver of autism prevalence increases is due to the recognition of children considered high-functioning or having Aspergers Syndrome. Overall, this report shows that all IQ groups are experiencing rising rates."
Overall, the CDC found, children born in 2016 were 1.6 times as likely to receive an ASD diagnosis or special education classification by 4 years of age compared with children born in 2012.
The report also analyzed the effects of the COVID-19 pandemic on the number of evaluations and ASD identifications before and after the onset of the pandemic.
"Before the pandemic, 4-year-old children were receiving more evaluations and identifications than 8-year-old children did when they were 4 years of age," the CDC stated. "However, these improvements in evaluation and ASD detection were wiped out beginning in March 2020. Delays in evaluation could have long-lasting effects as a result of delays in identification and initiation of services during the COVID-19 pandemic."
ASD prevalence per 1,000 children aged 8 years ranged from a high of 44.9 in California to a low of 23.1 in Maryland, but numbers were climbing in Maryland as well - 1 in 43 compared to 1 in 49 children in 2018.
Astonishingly, in California, 4.5% of 8-year-old children were identified with ASD in 2020, compared to the 2.8% figure nationally. That is a 1-in-22 prevalence rate.
New York-New Jersey study
Underscoring the grim national numbers, a Rutgers study released this past January showed a skyrocketing autism rate in the New York-New Jersey metro region. Documented cases of ASD in the New York-New Jersey metro region increased by as much as 500% between 2000 and 2016.
Contrary to previous findings, the highest increases were among children without intellectual disabilities.
"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% of children with autism also have intellectual disability. What our paper shows is that this assumption is not true."
In fact, Shenouda said, in this study, two-in-three children with autism had no intellectual disability whatsoever. Estimates in the early 2000s indicated that around half of children with autism also had intellectual impairments.
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%) had an intellectual disability; 2,764 (59.3%) did not, Rutgers states.
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.
However, Walter Zahorodny, associate professor at the Rutgers New Jersey Medical School and senior author on the study, said the numbers speak to significant and real increases in the disorder.
"Better awareness of and testing for ASD does play a role," Zahorodny said. "But the fact that we saw a 500% 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. ... This is a true increase. It constitutes a major public health crisis."
ASD prevalence has been shown to be associated with race and socioeconomic status, the researchers said. The Rutgers study identified that black children with ASD and no intellectual disabilities were 30% less likely to be identified compared with white children, while kids living in affluent areas were 80% more likely to be identified with ASD and no intellectual disabilities compared with children in underserved areas, the report stated.
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