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NEW YORK (Reuters Health) - Siblings of kids with autism have a higher risk of being diagnosed with the disorder than previously believed, suggests a new study.
The analysis of more than 600 three-year-olds with an older autistic sibling found that almost one in five of them had an autism spectrum disorder, which includes Asperger's syndrome and similar conditions.
That suggests pediatricians need to keep an extra eye on those siblings, even as toddlers -- because early interventions with therapy and extra support might help keep their symptoms to a minimum, researchers said.
"We know that the brain at young ages is more amenable to change," said study author Wendy Stone, of the University of Washington Autism Center in Seattle.
"When children are showing signs (of autism) even before the diagnosis is official, we need to start thinking about, how can we help parents within the course of their everyday activities to promote their child's social and emotional development?" she told Reuters Health.
The findings, she said, also show that autism rates -- now estimated at about one in every 110 U.S. kids -- probably aren't going to decrease anytime soon.
Previous studies estimated that between 3 and 14 percent of autistic kids' younger siblings also had the condition.
Stone and her colleagues had the advantage of a large data set of kids with autism and their siblings, including 664 sibling infants seen at 12 different institutions. They recruited the young siblings to the study when most were younger than six months old, before they showed any symptoms.
Around their third birthday, doctors tested each of those kids for signs of autism.
By that point, 132 of the siblings, or close to 20 percent, had developed an autism spectrum disorder, the researchers report in Pediatrics.
Kids who had multiple older autistic siblings were twice as likely to be diagnosed with autism as those with only one sibling with autism. As has been shown before, boy siblings were also about three times more likely than girls to have autism.
Researchers have long known that genes play a role in predisposing kids to autism, but it's clear that "genetics is not the whole story," Stone said -- and there are still many unanswered questions about what causes the condition.
GUIDING PARENTS' DECISION-MAKING
Keely Cheslack-Postava, an autism researcher from Columbia University in New York, said that the rate of autism in siblings may be higher now because the definition of who has an autism spectrum disorder has widened to include more kids.
Still, she said, the one-in-five number "for an individual family is somewhat limited in terms of exactly what this information means," she told Reuters Health.
Stone and her colleagues said that it's important that parents of an autistic child have access to genetic counseling if they're thinking of having another kid -- but added that it's hard for doctors to evaluate each family's individual risk of having another autistic child.
What this does is "puts a much better estimate of risk in the hands of parents and clinicians, so hopefully that will help guide their decision-making more effectively," said Zachary Warren. He's the head of the Treatment and Research Institute for Autism Spectrum Disorders at the Vanderbilt Kennedy Center in Nashville, Tennessee -- one place where kids were recruited for the study.
Cheslack-Postava, who like Warren did not work on the new report, agreed with the authors that one of the key messages to come from the findings is the importance of early intervention for at-risk siblings.
"The most important public health implication of this higher observed recurrence risk is probably for awareness and attention to development in those children, in order to facilitate intervention as early as possible for children who could benefit from it," she said by email.
Researchers agreed that more work needs to be done to figure out what kinds of interventions might be most helpful for kids with the first signs of autism.
The research network is funded by Autism Speaks, an organization that promotes awareness of autism and funds research into prevention and treatments.
SOURCE: bit.ly/jsoh2P Pediatrics, online August 15, 2011.