An estimated 1 in 88 children nationwide is believed to have autism or a related condition, a 23 percent jump in prevalence since government investigators last checked, the Centers for Disease Control and Prevention said Thursday.

It is the highest estimate ever assessed by the CDC, which for years has been tracking an increasing prevalence of autism spectrum disorders among school-age children.

"This is a national emergency and it's time for a national strategy," said Mark Roithmayr, president of the advocacy organization Autism Speaks, who addressed a CDC news briefing Thursday.

When prevalence data were last released in 2009, the CDC estimated 1 in 110 children were affected. In 2002, the agency estimated prevalence at 1 in 155. Boys, according to the new data, have autism at a rate of 1 in 54, nearly five times that of girls, whose rate is estimated at 1 in 252.

Looming over autism's rising prevalence are questions by some experts about whether the numbers reflect a genuine increase.

Dr. Andrew Adesman, chief of developmental and behavioral pediatrics at Cohen Children's Medical Center in New Hyde Park, said the new CDC data show autism spectrum disorders have risen by a staggering 78 percent in the past decade. He thinks there are several explanations for the escalating trend.

"Some of this increase is likely explained by the inclusion of milder forms of autism and by greater public and professional recognition of the disorder," Adesman said. "There also may be a true rise in the incidence.

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"If parents are concerned about the way their child plays, learns, speaks or acts, they should discuss this with their pediatrician," Adesman added.

"If families are still concerned, they may ask for a referral to a specialist for a more in-depth evaluation."

Published in today's issue of the CDC's Morbidity and Mortality Weekly Report, the research is based on 2008 health and school records of 337,093 8-year-olds at 14 study sites around the country. The closest one is in New Jersey.

It is estimated there are thousands of children on Long Island with autism-spectrum disorders, but there has been no official count completed to date.

The study population represented 8.4 percent of all children of that age in the United States in 2008.

From those records, clinicians confirmed 3,820 children met the government's definition of an autism spectrum disorder. Further analysis revealed 11.3 of every 1,000 children in the study had an autism-related condition.

From those numbers, researchers were able to calculate the 23 percent increase since their last report.

"The 1 in 88 [prevalence rate] does refer to our 14 communities," said Dr. Coleen Boyle, director of the CDC's national developmental disabilities center. However, she added that figure comes from such robust research, it can be extrapolated to the entire country.

CDC researchers found some of the most noteworthy increases in autism-related disorders occurring among black and Hispanic children. In previous CDC studies, minority children had not been as widely studied.

Their prevalence rates, however, were lower than those of white children. All told, 12 out of every 1,000 white children were found to have an autism-related condition compared with 10.2 per 1,000 among blacks and 7.9 per 1,000 among Hispanics.

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Dr. Martha Herbert, a Harvard University autism expert, Thursday suggested myriad factors, including environmental exposures, might help explain the uptick in autism.

Scientists at Cold Spring Harbor Laboratory are in the vanguard of researchers worldwide pursuing a genetic explanation for autism-related conditions.