On October 5, 2009, researchers with the Health Resources and Services Administration (HRSA), Centers for Disease Control and Prevention (CDC), and Massachusetts General Hospital published a new estimate of the prevalence of autism spectrum disorders (ASD) among children in the United States. Published online ahead of print in Pediatrics, the new estimate that roughly 1 in 90 U.S. children ages 3–17 were given an ASD diagnosis in 2007 is significantly higher than previous reports.
But, this finding is consistent with previous reports that the prevalence—the number of people diagnosed with a particular condition at a given time—of ASD is increasing. Epidemiological studies and surveys from the early 1990s estimated that 1 in 1500 children had autism. In 2002, this figure increased to 1 in 150.
The prevalence rate of 1 in 90 is based on telephone interviews of parents who were asked about a diagnosis of ASD. Children were not assessed independently to verify the parents’ reports. There were no earlier figures using this survey approach for comparison, although a separate survey conducted by the CDC also reports roughly 1 in 100 children with the diagnosis in 2006, up from earlier reports in 2002. As noted in the Pediatrics paper, there are many possible explanations for this trend, including a change in study methods to include a wider range of ASD diagnoses, improved screening and diagnostic tools which may allow healthcare providers to identify more cases of ASD and at earlier ages, as well as increased public awareness which may encourage more parents to bring their children in for diagnosis when they suspect their child has ASD.
This new estimate does not necessarily indicate a rising incidence—the number of new cases over a given time span—for ASD. Specifically, it is unclear from the report in Pediatrics whether the 1 in 90 estimate is measuring a true increase in ASD cases or improvements in our ability to detect it.
The question is not whether diagnosis and awareness has changed, but how much of the reported increase can be explained by changes in diagnosis and awareness, and how much of the reported increase is due to a rising incidence. One recent study using disability services data for California estimated that 24 percent of the increase in prevalence can be attributed to the changing diagnostic criteria for ASD, including its use with other developmental disabilities.1 While other factors appear to explain additional fractions of the increase in prevalence, there is still no complete explanation for the increase from 1 in 1500 to potentially 1 in 100 based on any of these factors. Thus, we cannot exclude the possibility that reports of increased prevalence reflect real increases in the numbers of children affected. Additional research will need to investigate this possibility using careful, consistent clinical assessments, carried out over a period of time in a well-defined population.
Regardless of whether the rate is 1 in 150 or 1 in 100, ASD presents a major challenge to public health. As more children are labeled or diagnosed with these disorders, there is a need to ensure they have access to and receive appropriate and personalized medical, educational, occupational, and social services throughout their lives.
The National Institutes of Health (NIH), is dedicated to responding to this challenge by supporting robust and innovative research that will lead to better ways to identify, treat, and even prevent the disabling symptoms of ASD and to help improve the quality of life for people with ASD and their families.
To date, NIH has obligated more than $85 million over two years through the American Recovery and Reinvestment Act (Recovery Act) to support autism research, in addition to the roughly $122 million in grants awarded in Fiscal Year 2009 through NIH’s original base funding. Much of this funding has gone into supporting studies that directly address research objectives identified by the Interagency Autism Coordinating Committee (IACC) Strategic Plan for Autism Spectrum Disorder Research.
As the current lead agency for the IACC as well as for autism research at NIH, the National Institute of Mental Health (NIMH) has dedicated significant resources toward this effort. For example, NIMH will be contributing more than half the total support for the largest funding opportunity for ASD research to date, which is also the only disease-specific initiative among all of NIH’s Recovery Act activities. Additional Recovery Act funds have been committed to ASD-related Challenge Grant and Grand Opportunities awards as well. Topics to be studied range from searching for genetic vulnerabilities that may be triggered by specific environmental factors to assessing service needs throughout the lifespan, and exploring barriers to timely diagnosis and treatment in urban settings.
Even before these new prevalence estimates were published, NIH and NIMH were increasing their investment in ASD research. Working together with other Federal agencies, in collaboration with advocacy groups and other community partners, NIH and NIMH will continue to support the best available research to pursue the best possible solutions for helping people with ASD to live the lives they want to lead.
King M, Bearman P. Diagnostic change and the increased prevalence of autism. Int J Epidemiol. 2009 Oct;38(5):1224-34. Epub 2009 Sep 7. PubMed PMID: 19737791.