Autism Prevalence Up, But Not Spiking

Typo in Pediatrics inflates increase in autism

by F. Perry Wilson MD, MSCE

The paper contains a jarring statement: the rate of autism spectrum disorder rose by "almost 400%" from 2007 to 2011, but the statement is wrong.

The paper in question is published online today by Pediatrics, but a close review of the data revealed that the number was drastically inflated.

The study used data from the National Survey of Children's Health, a telephone-based survey conducted in 2003, 2007, and 2011-2012 that asked parents about a host of their children's health conditions, including autism spectrum disorder. But the wording of the question changed significantly over that period of time.

In 2003, the question asked: "Has a doctor or health professional ever told you that [CHILD's NAME] has any of the following conditions?" "Autism" was then listed among various other conditions including diabetes, asthma, and depression.

From 2007 on, the question asked: "Has a doctor or other health care provider ever told you that [CHILD] had autism, Asperger's Disorder, pervasive developmental disorder, or other autism spectrum disorder?"

As the latter would be expected to generate more affirmative responses, the authors state in the manuscript that they ignored data from 2003 when calculating the rate of change in ASD prevalence.

However, when calculating the 400% increase, the authors compared the data from 2003 (when the estimated prevalence was 0.5%) to 2011 (when the estimated prevalence was 2.3%). They erroneously state that the prevalence in 2007 was 0.5%, which was in fact the 2003 rate. The true rate in 2007 (using the new question) was 1.9%. When contacted by email the corresponding author, Amy Houtrow, MD, PhD, MPH of the University of Pittsburgh, confirmed that this was a typo.

Given that the prevalence was 1.9% in 2007 - the earliest time-point with the more broad question phrasing - the increase in ASD is closer to 20% than to 400%.