Abstract
This study estimates the current prevalence of autism spectrum disorder among US children and adolescents from 2014 to 2016 using nationally representative data from the National Health Interview Survey.
Autism spectrum disorder (ASD) is a serious neurodevelopmental disorder resulting in a substantial burden for individuals, families, and society.1 Previous surveys have reported a steady increase in ASD prevalence in US children over the past 2 decades.2,3,4 However, the most recent estimate from the Autism and Developmental Disabilities Monitoring (ADDM) Network for the first time reported a plateau in ASD prevalence (1.46%) in 2012, after documenting a continuous increase from 0.67% in 2000 to 1.47% in 2010.2 In this study, we analyzed nationally representative data to estimate current prevalence of ASD among US children and adolescents in 2014-2016.
Methods
The National Health Interview Survey (NHIS)5 is a nationally representative annual health survey in the United States. The NHIS was approved by the research ethics review board of the National Center for Health Statistics and US Office of Management and Budget. All respondents provided oral consent prior to participation. The University of Iowa institutional review board determined that the current study was exempt based on the use of deidentified data.
The NHIS collects data on a broad range of health topics through in-person household interviews. For each interviewed family in the household, 1 sample child, if any, was randomly selected by a computer program. Information about the sample child was collected by interviewing an adult, usually a parent, who was knowledgeable about the child’s health. In NHIS 2014-2016, the total household response rate ranged from 67.9% to 73.8%, and the conditional response rate for the sample child component ranged from 91.2% to 92.3%. From 2014 to 2016, respondents were asked: “Has a doctor or health professional ever told you that [the sample child] had autism, Asperger’s disorder, pervasive developmental disorder, or autism spectrum disorder?” Responses for children and adolescents aged 3 to 17 years were included.
Prevalence estimates were weighted using survey procedures in SAS (SAS Institute), version 9.4. The sample weights took into account unequal probabilities of selection and nonresponse. P values for overall differences across strata were calculated using the F test. Trends in prevalence were tested using a logistic regression model with sample weights, which included survey year as a continuous variable, and adjusted for age, sex, and race/ethnicity. A 2-sided P value less than .05 was considered statistically significant.
Results
Of all eligible participants aged 3 to 17 years in the NHIS 2014-2016, 28 (0.09%) had missing information on ASD diagnosis and were excluded. Among the included 30 502 US children and adolescents, 711 were reported to have been diagnosed as having ASD. The weighted prevalence of ASD was 2.47% (95% CI, 2.20%-2.73%). The prevalence was 3.63% (95% CI, 3.19%-4.08%) in boys and 1.25% (95% CI, 0.99%-1.51%) in girls; 1.82% (95% CI, 1.42%-2.22%) in Hispanic children and adolescents, 2.76% (95% CI, 2.39%-3.13%) in non-Hispanic white children and adolescents, and 2.49% (95% CI, 1.69%-3.29%) in non-Hispanic black children and adolescents (Table). Across the 3-year reporting period, the prevalence was 2.24% (95% CI, 1.89%-2.59%) in 2014, 2.41% (95% CI, 1.98%-2.84%) in 2015, and 2.76% (95% CI, 2.20%-3.31%) in 2016 (P for trend = .11) (Table).
Table. Prevalence of ASD in US Children and Adolescents, 2014-2016.
| Characteristic | No. With ASD/Total | ASD, % (95% CI)a | P Value |
|---|---|---|---|
| Overall | 711/30 502b | 2.47 (2.20-2.73) | |
| Age, y | |||
| 3-11 | 403/17 267b | 2.49 (2.16-2.83) | .81c |
| 12-17 | 308/13 235b | 2.43 (2.06-2.81) | |
| Sex | |||
| Male | 545/15 727b | 3.63 (3.19-4.08) | <.001c |
| Female | 166/14 775b | 1.25 (0.99-1.51) | |
| Race/ethnicityd | |||
| Hispanic | 140/8111b | 1.82 (1.42-2.22) | .02c |
| Non-Hispanic white | 405/14 900b | 2.76 (2.39-3.13) | |
| Non-Hispanic black | 89/4038b | 2.49 (1.69-3.29) | |
| Other | 77/3453b | 2.48 (1.77-3.19) | |
| Geographic region | |||
| Northeast | 145/4742b | 3.03 (2.39-3.68) | .27c |
| Midwest | 148/6058b | 2.45 (1.91-2.98) | |
| South | 234/10 775b | 2.37 (1.87-2.88) | |
| West | 184/8927b | 2.26 (1.84-2.68) | |
| ASD prevalence by year | |||
| 2014 | 237/11 082 | 2.24 (1.89-2.59) | .11e |
| 2015 | 240/10 183 | 2.41 (1.98-2.84) | |
| 2016 | 234/9237 | 2.76 (2.20-3.31) |
Abbreviation: ASD, autism spectrum disorder.
Prevalence estimates were weighted.
Unweighted number of participants involving all 3 years.
P value for overall differences in prevalence by strata.
Race and Hispanic ethnicity were self-reported and classified based on the 1997 Office of Management and Budget Standards.
P value for trend.
Discussion
In a large, nationwide population-based study, the estimated ASD prevalence was 2.47% among US children and adolescents in 2014-2016, with no statistically significant increase over the 3 years. The observed prevalence was higher than estimates in previous years from the ADDM,2 although differences in study design and participant characteristics may partly explain the prevalence differences. For example, the NHIS was based on a nationally representative population, whereas the ADDM was conducted in selected sites. The NHIS was based on parent report of a physician diagnosis, whereas the ADDM was based on clinician review of education or health care evaluations. In the NHIS, the question about ASD changed in 2014,3 so the NHIS cannot be used to evaluate trends in ASD prevalence over a longer time. Another limitation is the ascertainment of ASD by the household respondents’ self-reports of physician diagnosis.
Changes in nonetiologic factors6 (such as diagnostic criteria, public awareness, and referral), as well as in etiologic factors1 (including genetic and environmental risk factors), have been postulated to account for the previously observed increase in ASD prevalence. Continued monitoring of the prevalence and investigation of changes in risk factors are warranted.
Section Editor: Jody W. Zylke, MD, Deputy Editor.
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