The report said the U.S. rate of autism spectrum disorder rose to about 1 in 88 children. The previous rate was 1 in 110. The new figure, which is from 2008 data, means autism is nearly twice as common as officials said it was five years ago. It indicates a 23-percent rise over a two-year period.
Researchers followed 337,000 8-year-olds at 14 different sites. Boys with autism continue to outnumber girls. According to the study, 1 in 54 boys in the U.S. have autism. For girls, it's about 1 in every 252.
Researchers and community advocates say the new report underscores what they've been saying all along: Autism in America is an epidemic and a public health crisis. Experts agree that the numbers are sure to affect research, treatment and the availability of services to families.
Health officials believe much of the increase is due to better recognition of cases, and they also say a broader definition of autism is a factor.
For decades, the diagnosis was given only to kids with severe language and social impairments and unusual, repetitious behaviors, but the definition has gradually expanded. Autism is now shorthand for a group of milder, related conditions, including Asperger's syndrome.
Environmental factors like pre-term deliveries, air pollution and having babies later in life may also play a role.
"Advanced maternal age can typically have a higher risk for having a child with autism spectrum disorder," said Dr. Larry Yin, medical director of the Children's Hospital Boone-Fetter Clinic.
The report also shows a large increase among Hispanic children and African American children. Officials believe that part of the reason for that is also because parents are testing their kids earlier. The report supports a push for early intervention, but that takes money.
"The cost to families and to society is $126 billion a year," said Phillip Hain, executive director of Autism Speaks.
The latest CDC study is considered the most comprehensive U.S. investigation of autism prevalence to date. Researcher gathered data from areas in 14 states - Alabama, Arizona, Arkansas, Colorado, Florida, Georgia, Maryland, Missouri, New Jersey, North Carolina, Pennsylvania, South Carolina, Utah and Wisconsin. California was not included in the report.
Higher autism rates were found in some places than others. There were fewer cases in Alabama than in Utah, for example, but the difference was attributed to less information out of Alabama.
Experts stress that parents need to look for early signs in their children. Autism is diagnosed by making judgments about a child's behavior; there are no blood or biologic tests.
Although autism is difficult to diagnose before 2 years of age, some warning signs might surface between 12 and 18 months. For example, infants should be able to maintain eye contact, and typically, a 1-year-old should turn when they hear their name.
The lack of those signs does not automatically suggest a diagnosis of autism, but they can be noted to discuss with your pediatrician.
The Associated Press contributed to this report.