The phenomenon, called developmental regression, occurs when children have reached milestones such as saying words and walking, and then those skills suddenly vanish. The new research found that the odds of developmental regression were twice as high for black children and 1.5 times higher for Hispanic children than they were for white youngsters.
It's estimated that one-third of children with autism go through developmental regression, said lead researcher Dr. Adiaha Spinks-Franklin, of Baylor College of Medicine and Texas Children's Hospital in Houston.
"They learn to babble or talk, then stop. They learn to play patty-cake, then stop," said Spinks-Franklin.
This appears to be the first study to show racial disparities in rates of developmental regression. And for now, the cause is unclear, Spinks-Franklin said.
No one knows why regression happens at all, said Dr. Dan Coury, medical director for the Autism Speaks Autism Treatment Network.
"But it does make us wonder if it might be a different type of autism, with different causes," Coury said.
Autism is a developmental disorder that -- to widely varying degrees -- impairs a child's ability to communicate and interact socially. Some kids have relatively mild problems relating to other people; others speak very little or not at all, and focus obsessively on only a couple of interests and engage in repetitive behaviors.
Researchers have managed to find a few hundred genes related to autism risk, and experts believe the disorder arises from a complex mix of genes and environmental exposures -- though it's not yet clear what those exposures are.
Coury said future studies could look into whether genes play a role in minority children's higher rate of regression. Another question, he said, is whether their parents might have had different environmental exposures before and during pregnancy.
Researching those possibilities, Coury noted, could also give clues to the causes of autism in general.
The current findings are based on 1,353 preschool children included in the Autism Speaks Autism Treatment Network (ATN) database. The children were from 17 different areas across the United States and Canada.
Based on parents' reports, 27 percent of the children had reached certain early milestones, such as saying words or making eye contact, then lost those skills.
Black and Hispanic parents were more likely to report lost skills, even when the researchers took into account for parents' education levels, whether they had insurance, and whether their child had already been diagnosed with autism before coming to the ATN.
It's already known there are other racial disparities in autism, Spinks-Franklin pointed out. Black and Hispanic children are typically diagnosed later than white children are -- whether they have developmental regression or not, Coury noted.
One reason, he said, is that minority families may have less access to health care.
According to the U.S. Centers for Disease Control and Prevention, children should be screened for developmental delays during routine "well-child" visits -- at the ages of 9 months, 18 months, and 24 or 30 months.
Autism can be difficult to diagnose, the CDC says, but can sometimes be detected by the age of 18 months. By age 2, a diagnosis from an experienced professional can be considered "very reliable," the agency says. Yet many children don't receive a definite diagnosis until school age.
That's something experts want to change. "The earlier we intervene, the better the outcomes," Coury said. "And that's pretty universal, whether children have regression or not."
Early intervention therapies start by age 3, and focus on building kids' language, movement and social skills.
Spinks-Franklin agreed that timely diagnosis is critical. "It's important for parents to be aware of the signs of autism," she said.
If you're worried about possible delays in your child's development, talk to your doctor, Spinks-Franklin advised. And if your child seems to have lost a skill, she added, that's a "red flag."
"In that case, don't hesitate to talk to your doctor," Spinks-Franklin said.
The findings from this study were presented on Tuesday at the Pediatric Academic Societies annual meeting in Vancouver. Findings presented at meetings should be considered preliminary until they've been published in a peer-reviewed journal.
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