As many as one in 50 US school age children have a diagnosis of autism, up 72 percent since 2007, but much of the increase involves milder cases, suggesting the rise is linked to better recognition of autism symptoms and not more cases, government researchers said.
Overall, the telephone survey of more than 100,000 parents found about 2 per cent of children ages 6 to 17 have autism, up from 1.16 per cent in 2007, the last time the study was conducted.
"That translates to 1 million school age children ages 6 to 17 who were reported by their parents to have autism spectrum disorder," said Stephen Blumberg, a senior scientist at the National Center for Health Statistics, a part of the US Centers for Disease Control and Prevention, who led the study.
As with prior estimates, boys were much more likely to be diagnosed with autism than girls, with 1 in 31 school-age boys, or 3.2 per cent, having an autism diagnosis, compared with 1 in 143, or 0.7 per cent of girls, having a diagnosis. "Boys were more than 4 times as likely as girls to have autism spectrum disorder," Dr Blumberg said.
He said the increase among boys accounted for nearly all of the overall increase in autism diagnoses.
The new findings differ sharply from autism data released just a year ago by the CDC, which said 1 in 88 children in the United States had autism, a spectrum of disabilities that can range from highly functioning individuals to those with severe speech and intellectual disabilities.
In general, individuals with autism struggle with difficulties in communication, behavior and social interaction. In the current study, the researchers surveyed parents of children age 6 to 17 as part of the 2011-2012 National Survey of Children's Health or NSCH. They compared their findings to the same study done in 2007, which found 1 in 86 children had an autism diagnosis.
The estimate from last year involved a review of medical and educational records of 8 year olds in 14 sites around the country. Data in the records were last collected in 2008, so the finding of 1 in 88 is not far off from the 1 in 86 figure in 2007, the starting point of the current study.