Autism now affects 1 in every 68 children, a 30 percent rise since last reported two years ago, federal researchers found in a new multistate analysis.
The investigation also shows that boys are five times more likely to have an autism spectrum disorder than girls.
The findings are based on a wide-ranging examination of medical records and abstracts of school-based services provided 8-year-olds in 11 states.
Coleen Boyle, director of the National Center on Birth Defects and Developmental Disabilities, a division of the Centers for Disease Control and Prevention, said 8-year-olds were chosen because, by that age, everyone with an autism spectrum disorder usually will have been diagnosed.
Boyle emphasized during a telephone news briefing that the 1 in 68 figure can be extrapolated to reflect autism's prevalence for all affected people under age 21.
"It is really the best estimate the U.S. has for autism," Boyle said.
CDC scientists found wide gender, race and ethnicity differences in autism's prevalence. Boys have a prevalence rate of 1 in 42 compared with 1 in 189 among girls.
Additionally, white children are more likely to have an autism spectrum disorder and to be in behavioral therapy than either black or Hispanic children, Boyle said.
When Boyle and her colleagues issued their 2012 report, autism prevalence was estimated to be 1 in 88. In 2000, she said it was 1 in 150. She could not explain why the number of children with autism continues to climb.
Boyle acknowledged that better awareness of autism among physicians and other health care providers might help explain the jump. But the degree to which physician awareness factors into the 1 in 68 rate could not be explained, she said.
"We don't know the extent . . . [of] those factors," she said. "But we clearly know they do play a role."
The study focused on children who had reached age 8 in 2010 and the data are based on autism's definition in the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition -- the DSM-IV -- the now outdated 1994 volume of mental health definitions. The fourth edition was replaced by the DSM-V last year. The 2012 report had focused on children who had reached age 8 in 2008.
The DSM-V changed the definition of autism, eliminating Asperger syndrome and PDD-NOS, or pervasive developmental disorder not otherwise specified. Some medical professionals expected future analyses to reflect a lower prevalence of autism because of the revision.
On Long Island, autism and its economic impact have been a huge burden on families and schools, said Evelyn Ain, founder of the Developmental Advocacy Coalition in Hicksville.
Ain and other advocates have been lobbying state legislators to fund an epidemiological study that would produce a Long Island-specific autism prevalence rate, which Ain and other advocates say will probably be high.
"There are so many affected families," Ain said. "We have been pushing for this for years."
Dr. Andrew Adesman, chief of developmental and behavioral pediatrics at Cohen Children's Medical Center in New Hyde Park, said: "It's tragic that these numbers continue to increase and I think what's equally tragic is that many families don't have easy access to what is considered state-of-the-art therapies for children."Dr. Melissa Nishawala, medical director of the Autism Spectrum Disorders Clinical and Research Program at NYU School of Medicine in Manhattan, said differences based on ethnicity are likely due to white children having better access to medical care.
The analysis, she emphasized, was based on medical and school records.
"There's currently a big public health campaign underway to help black and Hispanic families to be aware of autism," she said, adding that an additional push is underway to encourage health professionals to better identify children who have not been diagnosed.
Autism spectrum disorders are marked by difficulties with speech language and social behavior. Some children with an autism spectrum disorder do not speak. Many have difficulty making eye contact and interacting with siblings or other children. Some indulge in repetitive behaviors, such as rocking back and forth for hours. Others wander from home.
Since 2011, 44 autistic children nationwide have died after wandering away from a safe environment, said Wendy Fournier, president of the National Autism Association, which is has headquarters in Massachusetts.
-- White children were about 30% more likely to be diagnosed with autism than black children and nearly 50% more likely than Hispanic youngsters.
-- About 46% of children with autism were classified as having IQ scores in the average or above-average range of intellectual ability (an IQ above 85).
-- The new report suggests most children are
diagnosed at age 4.