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Autism prevalence increases following changes to NHIS

Estimated prevalence of autism spectrum disorder increased from 2011 to 2014 following changes in developmental disabilities questions in the National Health Interview Survey, according to recent findings.

“In 2014, [National Health Interview Survey] revised its approach to asking about [autism spectrum disorder (ASD)]. The question wording was expanded to include more specific details on what constituted an ASD and to align with another national survey, the 2011–2012 National Survey of Children’s Health. Additionally in 2014, the ASD question was included in the survey as a standalone question that was verbally asked before the question on other [developmental delay], and after the question on [intellectual disability],” Benjamin Zablotsky, PhD, of the National Center for Health Statistics, and colleagues wrote. “Before this, the ASD question was included in a checklist of 10 conditions provided to the parent; the parent was asked to read the list and select any of the 10 conditions that a doctor or health professional had ever said their child had.”

Researchers used National Health Interview Survey data for 2011 to 2014 to assess changes in ASD prevalence estimates among children aged 3 to 17 years. Overall, 10,554 children completed interviews in 2011, 10,954 in 2012, 10,684 in 2013 and 11,091 in 2014.

The estimated prevalence of ASD was 2.24% based on 2014 data, significantly higher than the estimated annual prevalence of 1.25% based on 2011 to 2013 data.

Conversely, the prevalence of other developmental delay significantly decreased from 4.84% based on 2011 to 2013 data to 3.57% based on 2014 data.

Prevalence of intellectual disability did not significantly change from 2011 to 2013 (1.27%) to 2014 (1.1%).

“The findings suggest that changes to the ordering and wording of the developmental disabilities questions within [National Health Interview Survey] resulted in changes to the parent-reported prevalence of ASD and any other [developmental delay],” the researchers wrote. “Starting in 2016, [National Health Interview Survey] will include questions on the current prevalence of [intellectual disability], ASD, and other [developmental delay]. This addition will follow the existing developmental disabilities questions, so as not to disrupt analyses of trends since 2014, and it will help to align [National Health Interview Survey] estimates with other surveillance efforts, and minimize the potential for misdiagnosed cases to be captured within prevalence estimates.” – by Amanda Oldt

Disclosure: The researchers report no relevant financial disclosures.