Autism Rate Climbs Again
of data from the same network for 2006, when the estimated prevalence was one out of 111 children, and a 73% relative increase from 2002, according to a surveillance summary in Morbidity and Mortality Weekly Report .
But getting a firm grasp on the prevalence of ASD is tricky because of a lack of objective diagnostic markers and changes in clinical definitions over time, so it's unknown how much of the increase is real and how much is related to changing diagnostic criteria and better identification of cases.
CDC director Thomas Frieden, MD, MPH, noted on a conference call with reporters that doctors have gotten better at diagnosing autism and communities have gotten better at providing needed services.
"So at this point I think there is the possibility that the increase â¦ is entirely the result of better detection," Frieden said, while acknowledging the uncertainty.
Mark Roithmayr, president of Autism Speaks, a research and advocacy organization, argued that only part of the increase in prevalence could be explained by broader diagnosis, with about half of the rise still unexplained.
Roithmayr called autism an epidemic in the U.S., one that costs an estimated $126 billion each year.
"One thing the data tell us with certainty is that there are many children and families who need help," Frieden agreed.
The researchers collected data from the 14 sites of the Autism and Developmental Disabilities Monitoring (ADDM) Network, which conducts active surveillance of children who are 8 years old, the age at which ASD prevalence peaks.
Prevalence is estimated not on the basis of professional or family reporting of a diagnosis but on analysis of the children's evaluation records from multiple sources, including general pediatric health clinics, specialized programs for children with developmental disabilities, and special education programs in public schools.
Children are considered to have an ASD if they display behaviors consistent with autistic disorder, pervasive developmental disorder-not otherwise specified (PDD-NOS), or Asperger disorder.
The 2008 prevalence varied widely among the ADDM sites, from 4.8 per 1,000 children in Alabama to 21.2 in Utah.