Childhood autism rates are at the highest level since the Centers for Disease Control and Prevention began tracking the disorder in 2000, new data released Dec. 2 show.
The increase likely reflects improvements in diagnosis and identification of autism spectrum disorder (ASD), not an increase in incidence, study authors with the CDC’s Autism and Developmental Disabilities Monitoring (ADDM) Network told this news organization.
Using a new surveillance methodology, researchers found that 2.3% of 8-year-olds in communities in 11 states across the United States had an autism diagnosis in 2018, up from 1.9% in 2016.
A separate report on early identification in 4-year-olds shows that children born in 2014 were 50% more likely to receive an autism diagnosis or ASD special education classification by 48 months of age than those born in 2010, signaling improved early diagnosis.
Taken together, the data suggest efforts to raise awareness about autism are working, though researchers were quick to say much work remains.
“It was not surprising to me and in fact it was reassuring that the number of children diagnosed with autism is higher and is actually approaching prevalence of autism that has been noted in some national surveys of parents,” Stuart Shapira, MD, PhD, associate director for science in CDC’s National Center on Birth Defects and Developmental Disability, told this news organization.
“It means we’re doing a better job of identifying children, which helps to get them into services earlier so they can achieve their best developmental outcome.”
The studies, published online in Morbidity and Mortality Weekly Report, are the first to use a new ASD surveillance protocol that relies on ASD diagnosis or special education classification and billing codes and eliminates comprehensive records analysis by trained clinician reviewers.
Racial disparities
The updated methodology was less labor intensive and reduced the time it took to produce the report, but it is not without its critics, who claim the new protocol will undercount the number of children with ASD.
Created in 2000 and funded by the CDC, the ADDM Network is the only surveillance program in the United States that tracks the number and characteristics of children with ASD in multiple communities in the U.S.
When ADDM released its first report in 2007 from six states and based on data from the year 2000, ASD prevalence was 6.7 per 1,000 children, or 1 in 150 children.
In the latest report, which includes data from 2018, the autism prevalence rate across 11 states was 23.0 per 1,000 children, or 1 in 44 children.
That rate is closer to reported autism prevalence from the National Survey of Children’s Health and the National Health Interview Survey, both of which rely on parent-reported ASD diagnoses.
in Arizona, Arkansas, California, Georgia, Maryland, Minnesota, Missouri, New Jersey, Tennessee, Utah, and Wisconsin.
Children were counted as having autism if their records included an ASD diagnosis, a special education classification of ASD, or an ASD International Classification of Diseases (ICD) code. A total of 5,058 children met those criteria.
Rates of ASD ranged from a low of 1.7% in Missouri to 3.9% in California and were 4.2 times higher in boys than in girls. Just under half of the children with ASD were evaluated by age 36 months.
Although the overall ASD prevalence was similar among White, Black, Hispanic, and Asian/Pacific Islander children, the report highlighted a number of other racial disparities overall and in individual states.
For example, among those with ASD and data on cognitive ability, 35.2% had an intelligence quotient score of 70 or lower. Black children with ASD were far more likely to have an IQ of 70 or less (49.8%) than Hispanic (33.1%) or White (29.7%) children.
“The persistent disparities in co-occurring intellectual disabilities in children with autism is something that we continue to see and suggests that we need to better understand exactly what’s happening,” Matthew Maenner, PhD, an epidemiologist and autism surveillance team lead with the CDC’s National Center on Birth Defects and Developmental Disabilities, told this news organization.
Another long-standing trend observed again in the new report on prevalence among 8-year-olds is low ASD prevalence among Hispanic children. While the overall estimate showed similar autism rates, a closer review of state-level data reveals a different picture.
“In almost half of the sites, Hispanic children were less likely to be identified as having ASD,” he said. “This gets lost if you look only at the overall estimate.”