Continuing increase in prevalence reaffirms public-health crisis
In March, the Centers for Disease Control and Prevention (CDC) significantly revised the estimated prevalence of autism in the United States. The new number – 1 in 88 children.
This represents a 23 percent increase from the CDC’s previous estimate of 1 in 110 children, reported in 2009. It’s a 78 percent increase over the agency’s 2007 estimate of 1 in 150. Consistent with previous estimates, the updated numbers remained heavily skewed toward boys – affecting an estimated 1 in 54, compared with 1 in 252 girls.
“The CDC’s new estimates of autism prevalence demand that we recognize autism as a public health emergency warranting immediate attention,” said Autism Speaks Chief Science Officer Geraldine Dawson, Ph.D. “It is a crisis of epidemic proportions – and not just among children.” (See related Top Ten story: “Mounting Evidence of Critical Need for Adult Transition Support.”)
The CDC analysis comes from its Autism and Developmental Disabilities Monitoring Network, with sites in 14 states. The researchers reviewed the health and special education records of tens of thousands of 8 year olds in the 14 communities. They looked for a diagnosis of autism spectrum disorder (ASD) or the symptoms that would add up to one.
As in previous CDC reports, prevalence figures varied widely between sites – suggesting possible differences in screening programs and the availability of records. The researchers also found evidence of a persistent but narrowing gap between white and minority children. The estimated prevalence for white children was 1 in 83. This compared with 1 in 127 for Hispanics and 1 in 98 for African Americans. Here, too, the findings may reflect differences in community screening and services – rather than true differences in prevalence.
More research is needed to understand the situation and address persistent gaps, said Michael Rosanoff, M.P.H., Autism Speaks associate director of public health research and scientific review.
“More attention must be paid, not only to the increasing number of identified cases, but also to the cases still being missed,” he explained. “Autism Speaks is committed to closing the gap in access to early detection and early intervention services, particularly among ethnic minorities and other underserved communities.”
Evidence suggests that autism’s true prevalence in the United States may be considerably higher, he added. A 2011 South Korean study, for example, directly screened grade-schoolers for ASD rather than relying on medical or educational records. It found a prevalence of 1 in 38 among the schoolchildren, two-thirds of whom had previously gone undiagnosed. As such, they would have been missed by the records-review approach the CDC currently uses in its estimates.
Autism Speaks funded the South Korea study and is now funding a similar direct-screening study in South Carolina. It is doing so in collaboration with the CDC’s monitoring site in that state. “This project aims to not only improve the accuracy of autism prevalence estimates, but also to understand the factors that influence why we may be missing diagnoses,” Rosanoff said. Such factors may include differences in community awareness and access to autism screening and services.
“More than ever, these numbers compel us to redouble our investment in the research that can provide more accurate estimates in the U.S. and help us understand the causes of the increases in prevalence we have witnessed,” Dr. Dawson concluded.
Autism and Developmental Disabilities Monitoring Network Surveillance Year 2008 Principal Investigators. Prevalence of autism spectrum disorders--Autism and Developmental Disabilities Monitoring Network, 14 sites, United States, 2008. MMWR Surveill Summ. 2012; 61(3): 1-19.