Tarya Seagraves-Quee dresses her six year-old autistic son Joshua in their room at a motel in Cambridge, Massachusetts July 8, 2009. REUTERS/Brian Snyder

You may have heard the oft-quoted statistic that autism affects 1 in 150 US children. Turns out it's more like 1 in 91 -- and about 1 in 58 boys, according to new figures released Sunday.

That's an estimated 673,000 US children -- or approximately 1 percent of all U.S. kids, the researchers from the U.S. Centers for Disease Control and Prevention, Atlanta, and Harvard Medical School, Boston report in the journal Pediatrics.

Bob Wright, co-founder of the autism advocacy group Autism Speaks, told Reuters Health he's not at all surprised by the new figures. We've been screaming about the numbers going up; now there is a relatively complete recognition of it.

The statistical aspect of autism is just staggering, he said, and not enough is being done about it. If we had 1 in 58 boys getting swine flu, the country would be crazy, Wright said.

Autism is a brain disorder characterized by problems with social interaction, repetitive behavior and other symptoms. People with a mild version called Asperger's syndrome usually function relatively well in society, although they have problems relating to others. People with the most extreme symptoms may be unable to speak and may also suffer severe mental illness and retardation.

No one knows what causes autism -- it's generally thought to have genetic and environmental triggers -- and there is currently no good treatment.

Autism is an urgent public health concern, Dr. Ileana Arias, deputy director of CDC, told reporters on a conference call Friday ahead of public release of the data.

The new data, she said, confirm that a concerted effort and a substantial national response is warranted in addressing the issue.

On September 30, U.S. President Barack Obama promised a large infusion of funds into research on autism, as part of plans to spend $5 billion on medical and scientific research, medical supplies and upgrading laboratory capacity.

The new figures on autism cases stem from a 2007 telephone survey conducted jointly by the Health Resources and Services Administration (HRSA) and CDC.

More than 78,000 parents of children between the ages of 3 and 17 were asked whether they had ever been told by a health care provider that their child had autism, Asperger's syndrome, or another autism spectrum disorder (ASD).

Based on these parent reports, the prevalence of ASD in 2007 was 110 per 10,000 children aged 3 to 17 (or 1 in 91). The new estimates are far higher than previous estimates of 66 autism cases per 10,000 children (or 1 in 150).

We are extremely concerned about the apparent increase, Dr. Arias said, but she urged caution in interpreting it. Unfortunately, the information that we currently have doesn't allow us to give a true account of whether the apparent increase is an actual increase or the result of changes in the way we describe or diagnose ASD, she explained.

More inclusive survey questions, increased public awareness, and improved screening and diagnosis of autism are all possible reasons for the higher numbers, Dr. Michael D. Kogan of HRSA and colleagues report in Pediatrics.

They also report that boys were much more likely than girls to have autism, which has been shown previously, and white children were more likely than black children or multiracial children to have the disorder. 

Parents of half the children with autism described the condition as mild. Another third of parents described their child's condition as moderate, and the remaining parents described it as severe.

Approximately 38 percent of children seemed to have lost their autism -- their parents said they had once been told that their child had an autistic disorder but their child did not currently have the condition.

It's possible, the researchers say, that autism was initially suspected but subsequently ruled out and never truly diagnosed. The high rate of lost cases of autism among very young children (age 3 to 5) supports this line of thinking.

It's also possible that some children with developmental issues and learning disabilities may have been initially diagnosed with autism to qualify for special education and other services.

Children who had lost their autism were more likely to be diagnosed with other developmental or mental health conditions, such as attention-deficit/hyperactivity disorder, anxiety problems, or behavioral problems.

We are hopeful, Arias said, that the new data will raise awareness about (autism), will help improve early identification and intervention, will provide information for policy and service planning, and most importantly help us meet the growing needs of individual families and communities who are affected by autism and other developmental disorders.

SOURCE: Pediatrics, October 2009.