The number of autism cases in the United States appeared to jump dramatically in 2014 according to recently released estimates, but researchers said that changes in the format of the questionnaire likely affected the numbers.
The report from the Centers for Disease Control and Prevention and National Center for Health Statistics shows that the prevalence of autism in children ages 3 to 17 went up nearly 80 percent from 2011-2013 to 2014. Instead of 1 in 68 children having autism -- a number that has alarmed public health officials in recent years and strained state and school system resources -- researchers now estimate that the prevalence is now 1 in 45.
Lead author Benjamin Zablotsky, an epidemiologist at the NCHS, and his colleagues said that in previous years some parents of children diagnosed with autism spectrum disorder likely reported it as a developmental disability instead of or in addition to autism because it was listed first. The new questionnaire flips the two categories, which researchers said made the autism estimates more similar to ones from other sources.
As might be expected from this change, the prevalence of other developmental disabilities declined significantly from 4.84 percent based on 2011-2013 data to 3.57 percent in 2014.
The prevalence of intellectual disability did not significantly change and remains at 1.1 percent and the prevalence of any three of the conditions was constant across all surveys.
The high rates of autism among American children has been the source of much debate in recent years, with some experts attributing it to overdiagnosis and others expressing concern about possible environmental factors affecting children's brain development.
Michael Rosanoff, an epidemiologist who is the director for public health research for Autism Speaks, an advocacy group, said that the new number "is likely a more accurate representation of autism prevalence in the United States" than the 1 in 68 number.
"This means that 2 percent of children in the U.S. are living with autism," Rosanoff said in a statement."The earlier they have access to care, services and treatment, the more likely they are to progress."
As in previous years, most of the children being diagnosed with autism are male, non-Hispanic white, living in large metropolitan areas, with two parents and with at least one parent with more than a high school education. Many more boys are being diagnosed with autism than girls, but the gap is narrowing somewhat. In 2011-2013 81.7 percent of all children diagnosed were male while 18.3 percent were female. In 2014, it was 75 percent male, 25 percent female.
Most of the children being diagnosed with autism were identified by their parents as non-Hispanic white. More than two-thirds of children being diagnosed lived with two parents.
Children being diagnosed represented a wide range of incomes. Most of the children being diagnosed had at least one parent with more than a high school education -- a phenomenon that experts have said could be due to the fact that they may be more likely to notice issues early on and seek medical help.
More than half of children diagnosed live in large metropolitan statistical areas that include places like New York, Los Angeles and Washington.