Children born in 2014 were 50% more likely to receive an autism diagnosis or special education by age 4 than those born in 2010. Early detection could help improve access to intervention measures and may help improve developmental outcomes, according to the researchers.
“The substantial progress in early identification is good news because the earlier that children are identified with autism, the sooner they can be connected to services and support,” said Dr. Karen Remley, director of the CDC’s National Center on Birth Defects and Developmental Disabilities. “Accessing these services at younger ages can help children do better in school and have a better quality of life.”
Overall in 2018, about 1 in 44 8-year-olds (2.3% of 8-year-olds) had been identified with autism spectrum disorder, according to one of the CDC studies. Prevalence was more than four times higher among boys than girls, but similar across most racial and ethnic groups. Trends in prevalence by local income level varied by community.
While early detection has improved, autism was less common among 4-year-olds in 2018 than among 8-year-olds, even when accounting for suspected cases, the other CDC study found. This means that many children who will later be diagnosed with autism do not have documented concerns before age 4, according to the researchers.
One exception to this was in California, where the participating community had a higher documented incidence rate by age 4 than any of the other 10 communities. The researchers note that there are efforts to promote early identification in the area, with one program that has trained hundreds of pediatricians to utilize wellness exams to screen children and recommend evaluation as necessary.
Generally, children who have intellectual disabilities are more likely to be diagnosed with autism earlier. According to the researchers, this finding suggests a need to better detect and evaluate developmental concerns beyond cognitive ability. A child was considered to have an intellectual disability if their IQ was 70 or lower or if explicitly noted during an exam.
This is especially true for Black children. Even by age 8, more than half of Black children diagnosed with autism also had an intellectual disability, compared to 35% of 8-year-olds with autism overall. Low IQ scores were also more common among Hispanic children diagnosed with autism than White children.
For these studies, CDC researchers analyzed data from 2018 for two cohorts of children: those born in 2010 who turned 8 in 2018 and those born in 2014 who turned 4 in 2018. The data was compiled from communities in 11 states that participate in the Autism and Developmental Disabilities Monitoring Network.
The latest data shows evidence of changing patterns in identifying autism in children by race and socioeconomic status.
In 2018, more communities saw higher prevalence rates among Black and Hispanic children than White children than in previous years. Communities with lower median household income also saw higher cumulative incidence rates of autism spectrum disorder diagnoses by age 4.
“These findings could indicate improvements in ASD (autism spectrum disorder) identification among historically underserved populations,” the researchers wrote.
The researchers note that the sample size is limited to the 11 participating communities and may not be broadly representative. Also, practices and policies differ by community, as do characteristics of the population analyzed, which may contribute to variability in findings.