Summary: Between children born in 2007 and 2013, autism diagnoses rose by 73% for Hispanic children, 44% for African American children and 25% for white children aged 3–5.
Source: University of Colorado at Boulder
Autism prevalence among racial and ethnic minority children in the United States has grown substantially in recent years. New research from the University of Colorado Boulder shows that Black children now have higher diagnosis rates than White children in most states, while Hispanic rates are increasing faster than any other group.
The peer-reviewed study, published in the Journal of Autism and Developmental Disorders, also reports that autism rates for White children, which had plateaued in the mid-2000s, are beginning to rise again.
Researchers say part of the increase reflects improved awareness and detection in historically underserved communities, but the pattern and pace of the rise suggest that other environmental or exposure-related factors may also be contributing.
“We found that rates among Black and Hispanic children are not only catching up to White children — who historically had higher rates — but in many places they now exceed them,” said lead author Cynthia Nevison, an atmospheric research scientist at the Institute of Arctic and Alpine Research. “These results indicate additional factors beyond a simple catch-up effect may be at work.”
Nevison and co-author Walter Zahorodny, an autism researcher and associate professor of pediatrics at Rutgers New Jersey Medical School, analyzed the most recent available data from two major U.S. surveillance sources: the Individuals with Disabilities Education Act (IDEA) database and the Autism and Developmental Disabilities Monitoring (ADDM) Network.
IDEA provides annual prevalence estimates, including race and ethnicity information, for 3- to 5-year-olds across all 50 states. ADDM reports prevalence among 8-year-olds in a subset of states on a biennial basis.
The study’s key finding is that for children born between 2007 and 2013, autism prevalence among 3- to 5-year-old Hispanics rose by 73%. During the same birth years, prevalence rose 44% for Black children and 25% for White children.
By 2012, the researchers found that in 30 states the prevalence among Black children exceeded that among White children. In states classified as “high prevalence,” the study reports that among children born in 2013 and diagnosed by ages 3–5, roughly 1 in 79 White children, 1 in 68 Black children and 1 in 83 Hispanic children had been identified with autism.
The authors note considerable variability among states. Some states, such as Colorado, fell into a “low-prevalence” category for the age 3–5 group. The report cautions that state-by-state differences likely reflect disparities in early detection and reporting practices; many children are diagnosed after age 5, so overall prevalence is higher than what early-childhood counts capture.
“There is no doubt that autism prevalence has increased significantly over the past 10 to 20 years,” Zahorodny said, “and based on this larger, more recent dataset we expect prevalence to continue to rise across all racial and ethnic groups in the coming years.”
The Centers for Disease Control and Prevention reported in 2018 that about 1 in 59 children of all races had been diagnosed with autism, and that overall rates had risen roughly 15% from the prior two-year period. The CDC attributed much of that increase to improved outreach and diagnosis among minority populations that historically received fewer evaluations.
However, Zahorodny emphasized that the new data do not fully support the idea that the recent increases are solely the result of improved awareness. “If minority rates are exceeding White rates, that implies a difference in risk — either greater exposure to an environmental factor or another trigger,” he said.
“If the minority rates are exceeding the white rates that implies some difference in risk factor, either greater exposure to something in the environment or another trigger.”
Established risk factors associated with autism include advanced parental age, maternal immune challenges during pregnancy, certain genetic mutations, premature birth and being a twin or part of a multiple birth. The authors stress that the current research cannot yet identify which, if any, specific environmental exposures explain the observed increases among minority children.
The study calls for further research to pinpoint possible environmental contributors and to improve understanding of why prevalence trends vary across racial and ethnic groups and among states. Better, more consistent early screening and reporting practices would also sharpen the picture of how autism prevalence is changing over time.
Source:
University of Colorado at Boulder
Media Contacts:
Lisa Marshall – University of Colorado at Boulder
Image Source:
The image is in the public domain.
Original Research: Open access
“Race/Ethnicity-Resolved Time Trends in United States ASD Prevalence Estimates from IDEA and ADDM”. Cynthia Nevison, Walter Zahorodny.
Journal of Autism and Developmental Disorders. doi:10.1007/s10803-019-04188-6
Abstract
Race/Ethnicity-Resolved Time Trends in United States ASD Prevalence Estimates from IDEA and ADDM
This study tracks race-specific time trends in Autism Spectrum Disorder prevalence among 3–5 year-olds and 8 year-olds identified by the U.S. Individuals with Disabilities Education Act (IDEA) and the Autism and Developmental Disabilities Monitoring (ADDM) Network. Historically, White ASD prevalence has been higher than other racial groups but plateaued for IDEA birth cohorts from about 2004 to 2007 before rising again. Black and Hispanic IDEA prevalence increased steadily and caught up to White levels by birth year roughly 2008 and 2013, respectively, with Black prevalence subsequently exceeding White prevalence in the majority of states. Plateaus in White prevalence appeared in some ADDM states for birth years 2002–2006, but IDEA trends suggest prevalence will increase across all racial groups in ADDM’s birth year 2008 report.