One in Fifty

Many posts have discussed the prevalence and incidence of autism.  NBC reports new data:

Two percent of U.S. schoolkids – or about a million children – have been diagnosed with some sort of autism, according to the latest government report released on Wednesday -- or at least their parents say they have. It’s a large increase since the last report but experts stress it doesn’t necessarily mean more children are developing autism.

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Tanya Paparella of the University of California Los Angeles Center for Autism Research and Treatment says she thinks it very possible that kids have been going undiagnosed.

“A child who is verbal, who has good language, who is highly intelligent – those are children where I think parents and even teachers and the layperson might not necessarily have thought that was a child with autism spectrum disorder,” says Paparella, who was not involved in the study.

“In the past, people really thought children on the autism spectrum had significant learning difficulties and we know now that is not necessarily the case. We know there are children who may be highly intelligent and do very well in areas of academics.” Such kids may have been seen merely as quirky, Paparella says.

The abstract:

Objectives—This report presents data on the prevalence of diagnosed autism spectrum disorder (ASD) as reported by parents of school-aged children (ages 6–17 years) in 2011–2012. Prevalence changes from 2007 to 2011–2012 were evaluated using cohort analyses that examine the consistency in the 2007 and 2011–2012 estimates for children whose diagnoses could have been reported in both surveys (i.e., those born in 1994–2005 and diagnosed in or before 2007).

Data sources—Data were drawn from the 2007 and 2011–2012 National Survey of Children’s Health (NSCH), which are independent nationally representative telephone surveys of households with children. The surveys were conducted by the Centers for Disease Control and Prevention’s National Center for Health Statistics with funding and direction from the Health Resources and Services Administration’s Maternal and Child Health Bureau.
Results—The prevalence of parent-reported ASD among children aged 6–17 was 2.00% in 2011–2012, a significant increase from 2007 (1.16%). The magnitude of the increase was greatest for boys and for adolescents aged 14–17.

Cohort analyses revealed consistent estimates of both the prevalence of parentreported ASD and autism severity ratings over time. Children who were first diagnosed in or after 2008 accounted for much of the observed prevalence increase among school-aged children (those aged 6–17). School-aged children diagnosed in or after 2008 were more likely to have milder ASD and less likely to have severe ASD than those diagnosed in or before 2007.

Conclusions—The results of the cohort analyses increase confidence that differential survey measurement error over time was not a major contributor to observed changes in the prevalence of parent-reported ASD. Rather, much of the prevalence increase from 2007 to 2011–2012 for school-aged children was the result of diagnoses of children with previously unrecognized ASD.