Researchers at the Johns Hopkins Bloomberg School of Public Health contributed to a new Centers for Disease Control and Prevention report examining autism among children who turned 4 and 8 years old in 2022. The CDC report, which includes data from 16 study sites across the U.S. including Maryland, found an overall prevalence of autism of 1 in 31 (3.2%) among 8-year-olds in 2022.
The Maryland study site, led by researchers at Bloomberg School’s Wendy Klag Center for Autism and Developmental Disabilities, found a prevalence of 1 in 38 (2.6%) among 8-year-olds and 1 in 41 (2.4%) among 4-year-olds in 2022. The Maryland data for 2022 were drawn from Baltimore, Carroll, Cecil, Harford, and Howard counties, as in prior surveillance years.
The CDC report was published online April 14. Key findings from the five-county Maryland site study of 2022 data include:
Black and Asian/Pacific Islander children had among the highest rates of autism in Maryland.
The number of 8-year-old girls identified as having autism surpassed 1%, with 1 in 93 having autism, for the first time in Maryland.
Boys were more likely than girls to have autism, in Maryland and across all 16 sites. In Maryland, these sex gaps were less pronounced in younger children.
The new CDC report reveals progress for identifying children with autism at a younger age in Maryland and in other network sites.
Autism spectrum disorder (ASD, or autism) is a developmental disability that is characterized by social and communication challenges, along with restrictive and repetitive behaviors and interests.
The CDC’s Autism and Developmental Disabilities Monitoring (ADDM) Network began collecting data on 8-year-olds in 2000 and among 4-year-olds in all sites in 2018. Data on autism is collected from health, education, and/or early intervention sources within each site’s study area. The CDC notes that the ADDM Network is not a representative sample of the entire U.S., and there is variability in prevalence estimates between sites. In this latest report, autism prevalence estimates across the Network’s 16 sites ranged from less than 1% in Texas (Laredo) to 5.3% in California in 2022.
The CDC’s ADDM Network reports have consistently reported that boys are significantly more likely than girls to be identified as having autism. The CDC report for 2020 reported that the prevalence for girls surpassed 1%. In the current report, among 8-year-olds across all Network sites, there are 3.4 boys with autism for every girl with autism, versus 2.8 boys for every girl among 4-year-olds. Among 8-year-olds in Maryland, there are 3.9 boys for every girl who has autism, versus 2.6 boys for every girl among 4-year-olds.
The new report also examines differences in autism prevalence by racial and ethnic background. In Maryland, the highest autism prevalence estimates among 8-year-olds in 2022 were observed in Black children (1 in 27), followed by Asian/Pacific Islander (1 in 32), multiracial (1 in 34), Hispanic (1 in 35), and white (1 in 52) children. These trends first emerged in Maryland for Black children in 2018 and were reported by the CDC in 2020 as a network-wide finding in 2023. The researchers found similar prevalence trends in 2022 by race and ethnicity among Maryland 4-year-olds and across the ADDM Network for both age groups.
“Years ago, we only knew that autism was impacting white males. This latest ADDM report, along with the one released in 2023, show that autism impacts everyone—including females and children from all racial and ethnic backgrounds,” says Elise Pas, PhD, MA, research professor in the Bloomberg School’s Department of Mental Health and one of the two Maryland ADDM Network site’s principal investigators.
More children in the U.S. are being identified as having autism by age 48 months, suggesting progress for early identification among children born more recently (e.g., 2018 births) than children born earlier (e.g., 2014 births). In Maryland, prevalence is comparable among the two age groups, which further signifies early identification progress. In the Maryland study, the researchers found a prevalence of 1 in 41 for children who turned 4 in 2022, and 1 in 38 for those who turned 8 in 2022. In comparing these two age groups, 4-year-olds were 1.8 times more likely to be identified with autism by 48 months than 8-year-olds. In past years, there were larger gaps between these two age groups.
“We’ve been continuously monitoring autism prevalence among 8-year-olds in Maryland for the past 20 years and expanded to include 4-year-olds more recently to monitor whether we have moved the needle on early identification,” says Christine Ladd-Acosta, PhD, one of two ADDM Network site principal investigators, and the vice director of the Bloomberg School’s Wendy Klag Center. “The data suggest that we are identifying children earlier, which should translate into needed supports for children and their families sooner, which will help them achieve their full potential.” Ladd-Acosta is also an associate professor in the Bloomberg School’s Department of Epidemiology.
The CDC ADDM Network expanded from 11 sites in 2020 to 16 sites in 2022. They include Arizona, Arkansas, California, Georgia, Indiana, Maryland, Minnesota, Missouri, New Jersey, Pennsylvania, Puerto Rico, Tennessee, Texas (2 sites), Utah, and Wisconsin. The Maryland ADDM Network site based at the Bloomberg School’s Wendy Klag Center is continuing surveillance of children in Baltimore, Carroll, Cecil, Harford, and Howard counties who were 4 and 8 years old in 2024.
The CDC recommends that parents track their child’s development from birth to age 5, and get their child screened if they have a concern. Free checklists and information for parents, physicians, and childcare providers are available at http://www.cdc.gov/ActEarly.
A full copy of the report, Prevalence and Early Identification of Autism Spectrum Disorder Among Children Aged 4 and 8 Years—Autism and Developmental Disabilities Monitoring Network, 16 Sites, United States, 2022, is available on the CDC website.
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