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Nearly 1 percent of US children have autism, report indicates

Better diagnosis, tracking might explain large rise

By Stephen Smith
Globe Staff / December 19, 2009

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Roughly 1 of every 110 children in the United States has been diagnosed with autism, with boys at least four times more likely than girls to suffer from the developmental disorder, according to a federal study released yesterday that served as a rallying cry for scientists and activists.

The new estimates from the US Centers for Disease Control and Prevention were based on a painstaking review of the 2006 medical and educational records of 8-year-olds in parts of 11 states and produced the most comprehensive portrait of the disease’s impact. No New England states were included in the study.

The autism rates in the report were significantly higher than figures gleaned from a review of 2002 records. But much as autism is a black box for its victims and their families, it remained unclear yesterday whether the increase in cases reflected better diagnosis and tracking or a true upswing in the condition’s prevalence.

“Some of the increases are due to better detection, particularly among children who may not have come to attention in the past,’’ including girls and Hispanic children, said Catherine Rice, lead author of the CDC study. “However, a simple explanation is not apparent. And a true increase in risk cannot be ruled out.’’

The findings in the CDC report mirror a study that appeared in the journal Pediatrics earlier this year that analyzed data gathered in a 2007 national survey of parents. That report found that about 1 percent of children between ages 3 and 17 had been diagnosed with the disorder. Recently published international studies have reported similar rates.

And the new federal report, much like previous studies, found that autism strikes boys with greater frequency: 14.5 of every 1,000 boys had autism, compared with 3.2 per 1,000 girls.

In recent years, few medical conditions of childhood have stoked deeper concern - and ignited greater controversy - than autism, which produces a wide spectrum of symptoms that can compromise learning and impair social interaction.

Unlike conditions such as obesity, diabetes, or and asthma, which can be identified with a scale, a blood test, or a breathing exam, diagnosing autism involves subtle and sophisticated assessments of behavior. As a result, rates of diagnosis can vary, sometimes depending on who performs the review and where.

In the federal study, for example, children in Miami were diagnosed with autism at a rate of 4.2 per 1,000. But in Phoenix, the rate was 12.1 per 1,000.

“Does that really mean three times as many children in Arizona have autism spectrum disorders as in Florida? Not necessarily,’’ said Dr. William Barbaresi, director of the Developmental Medicine Center at Children’s Hospital Boston.

One possible reason for the difference: In Miami, researchers had access only to medical records, while in Phoenix, medical and educational records were made available.

“It provides additional evidence,’’ Barbaresi said, “of the impact of identification strategies on the number you estimate for children affected by autism.’’

That number, based on earlier CDC studies, had stood at about 1 of every 150 children.

Advocacy groups seized on yesterday’s report as proof that scientists and the agencies that pay for research need to redouble efforts to better understand the roots of autism.

“The point is that we need to better explore both the role of genetics and environment and how they may interact with each other,’’ said Geraldine Dawson, chief science officer for the advocacy group Autism Speaks. “This study does underscore it’s a large increase, and we’re continuing to see this increase, and we don’t have answers for it.’’

Dr. Elizabeth Caronna, who directs Boston Medical Center’s autism clinic, said she suspects that much of the increase is attributable to heightened awareness of autism and more careful tracking of the disease by physicians.

Regardless of the reasons for the increase, said Dr. Ann Neumeyer of Massachusetts General Hospital, the finding should highlight the deep - and expensive - impact the disease will have.

“It helps us in understanding the amount of resources that are going to need to be set aside to help educate those children,’’ said Neumeyer, medical director of the Lurie Family Autism Center/LADDERS at Mass. General. “It also underscores the importance of making plans 20 years down the road when 1 percent of the population becomes adults.’’

Stephen Smith can be reached at stmith@globe.com.