As many as one in 68 U.S. children may have autism, U.S. health officials said on Thursday, a sharp increase over an estimate of 1 in 88 children just two years ago that raises questions about why the number has risen so dramatically.
Researchers at the U.S. Centers for Disease Control and Prevention noted in their report that the data, gleaned from a study of children in 11 communities, could not be generalized to the national population.
They also did not study why the rates were so much higher, but there are some clues. In the latest report, almost half of children identified as having autism also had average or above-average IQ levels, compared with just a third of children a decade ago.
“It could be doctors are getting better at identifying these children; it could be there is a growing number of children with autism at higher intellectual ability, or it may be a combination of better recognition and increased prevalence,” Coleen Boyle, director of the CDC's National Center on Birth Defects and Developmental Disabilities, said in a conference call.
Some experts believe the higher rates reflect a heightened focus on autism by parents, doctors and teachers that may be resulting in more children being diagnosed with the disorder.
In its latest report, the CDC studied medical, school and other records of 8-year-olds within 11 U.S. communities to determine whether a child had autism.
There were significantly different rates by region, ranging from 1 in 175 children in Alabama to 1 in 45 children in New Jersey, which could reflect access to healthcare and other factors.
The current study looked at fewer sites than the data reported in 2012, which included 14 communities, but the CDC said it did not change the criteria used to diagnose autism.
In this latest report, which looks at data from 2010, the researchers found 14.7 per 1,000 8-year-olds had autism, compared with the previous estimate of 11.3 per 1,000 8-year-olds in its 2012 estimate, which used data from 2008.
The CDC said the latest data continue to show that autism is almost five times more common among boys than girls, affecting 1 in 42 boys versus 1 in 189 girls.
White children are more likely to be identified as having autism spectrum disorder than are black or Hispanic children.
Dr Melissa Nishawala, medical director of the Autism Spectrum Disorders Clinical and Research Program at New York University's School of Medicine, said the new numbers do not necessarily mean that the incidence of autism in the United States is rising.
“I think the bulk of these increases are the way we define autism and the way we look for cases and how good we are at finding cases,” she said.
Nishawala said news reports about high rates of autism are increasing awareness, and the latest numbers from the CDC will likely mean even more people look for signs in children.