300,000 Children in U.S. Found to Have Autism
Friday, May 5, 2006
About 300,000 American children have been diagnosed as having autism, according to the first comprehensive national surveys of the developmental disorder.
Boys were four times more likely than girls to have the disorder, which is characterized by verbal, social and emotional problems. White families with higher incomes were also more likely to report having children with the disorder, a fact that federal experts said probably reflected unequal access to medical services.
The new data came in two surveys released yesterday by researchers at the Centers for Disease Control and Prevention, who said the numbers matched the range found by earlier studies that looked at smaller groups of people.
Autism has been dogged by controversy for more than a decade after what appeared to be a sharp increase in diagnoses in the 1990s. Many experts believe the increase reflects changes in diagnostic criteria adopted in 1994, increased public awareness of the problem, and the difficulties in telling apart a number of overlapping conditions that fall under an umbrella known as autism spectrum disorders. Some advocates have blamed a mercury-based preservative in children's vaccines, even though repeated analyses have failed to confirm a link.
The new surveys show that Hispanics have a much lower autism rate than whites, but experts said that this probably reflected differences in access to care.
"This does provide important results on the need to consider autism may be under-diagnosed in certain populations," said Laura Schieve, an epidemiologist at the National Center on Birth Defects and Developmental Disabilities, at a teleconference organized by the CDC.
Schieve and José Cordero, director of the birth defects center, said both surveys showed some differences in autism prevalence by age group -- with children ages 6 to 11 more likely to be diagnosed than those ages 4 to 5. However, they said the differences were not statistically meaningful and could not address whether the decision to phase out the mercury-based preservative from children's vaccines in 1999 had led to a leveling off or fall in autism diagnoses.
Cordero said it was far more likely that the age-group differences in prevalence reflected the fact that many children are not diagnosed until they enter school and teachers recognize the problem. That means the number of diagnoses among the 4-to-5-year-olds in the surveys could rise as they enter school.
"Let's do it again next year and the year after," said Gary Goldstein, president and CEO of the Kennedy Krieger Institute at Johns Hopkins University, which has a large autism research program. "My prediction is you are going to see a rise in the younger ones. If it was going away, which I would love, you would see a falling number."
Goldstein said the racial and class differences in diagnoses reflected the fact that getting a diagnosis often requires that parents be effective advocates, at least in the years before children arrive in school.
"It's not like leukemia or a broken bone where a diagnosis will be made no matter what your social class is," said Goldstein, who is also a board member at Autism Speaks, an advocacy group focused on research and awareness. "You have to be an advocate."
Peter Bell, chief executive of the Cure Autism Now Foundation, an advocacy group, said the fact that some children do not get diagnosed before they reach school is troubling. Early diagnoses, he said, allow for early interventions, which are more effective.
Two local researchers who have long claimed there is a link between the mercury additive thimerosal and autism said the CDC numbers suggest there is a connection. Mark and David Geier, a father-son team, said at the very least the CDC data showed a leveling off in autism diagnoses.
"In early 2003, we looked at a number of databases and how much mercury children were getting from their shots, and we said there is a causal relationship between thimerosal and autism," David Geier said. "Thimerosal started to be removed in July 1999. We predicted the rates of autism would begin to decrease. What we are seeing is decreasing trends. It coincides with children getting less mercury in their shots."