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Autism rates among racial minorities in the United States have seen double digit increases in recent years, a new study shows.

Rates for black children now exceed those of whites in most states and rates among Hispanics are growing faster than any other group, according to the study. The study also finds that the prevalence of autism among white youth is ticking up again, after flattening in the mid-2000s.

While some of the increase is due to more awareness and greater detection of the disorder among minority populations, the researchers say other environmental factors are likely at play.

“We found that rates among blacks and Hispanics are not only catching up to those of whites—which have historically been higher—but surpassing them,” says lead author Cynthia Nevison, an atmospheric research scientist with the Institute of Arctic and Alpine Research at the University of Colorado at Boulder. “These results suggest that additional factors beyond just catch-up may be involved.”

Researchers analyzed the most recent data available from the Individuals with Disabilities Education Act (IDEA) and the Autism and Developmental Disabilities Monitoring (ADDM) Network. IDEA tracks prevalence, including information on race, among 3-to-5-year-olds across all 50 states annually. ADDM tracks prevalence among 8-year-olds in 11 states every two years.

The new study found that between birth year 2007 and 2013, autism rates among Hispanics age 3 to 5 rose 73%, while rates among black children that age rose 44% and rates among whites rose 25%. In 30 states, prevalence among black children was higher than among whites by 2012.

In states with “high prevalence,” 1 in 79 whites, 1 in 68 blacks, and 1 in 83 Hispanics born in 2013 received an autism diagnosis by age 3 to 5.

Other states like Colorado fell in a “low-prevalence” category, but the authors caution that differences between states likely reflect differences in how well authorities report cases by age 3 to 5. Further, the real prevalence is substantially higher, as many children are not diagnosed until later in life, researchers say.

“There is no doubt that autism prevalence has increased significantly over the past 10 to 20 years, and based on what we have seen from this larger, more recent dataset it will continue to increase among all race and ethnicity groups in the coming years,” says coauthor Walter Zahorodny, an autism researcher and associate professor of pediatrics at the New Jersey Medical School at Rutgers University.

In 2018, the Centers for Disease Control reported that about 1 in 59 children of all races had an autism diagnosis and that rates had risen 15% overall from the previous two- year period, largely due to better diagnosis and outreach among historically underdiagnosed minority populations.

The new study challenges that explanation.

“Our data contradict the assertion that these increases are mainly due to better awareness among minority children,” says Zahorodny. “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, challenges to the immune system during pregnancy, genetic mutations, premature birth, and being a twin or multiple.

The authors say that, based on current research, they cannot pinpoint what other environmental exposures might factor into the increases in autism, but they would like to see more research done in the field.

The study appears in the Journal of Autism and Developmental Disorders.

Source: Rutgers University