Newswise — Researchers at the Johns Hopkins Bloomberg School of Public Health contributed to a new Centers for Disease Control and Prevention (CDC) report that estimates the prevalence of autism spectrum disorder (ASD) at 1 in 68 U.S. children overall, an increase of 29 percent since the last such report in 2012. Broken down by gender, the overall rate is 1 in 42 boys and 1 in 189 girls.
In Maryland, the overall rate is 1 in 60 children; 1 in 37 boys and 1 in 179 girls.
This is the fourth report by the CDC’s Autism and Developmental Disabilities Monitoring Network (ADDM), which has used the same surveillance methods for more than a decade. Previous ADDM reports estimated the rate of ASD at:
• 1 in 88 children in the 2012 report that looked at 2008 data
• 1 in 110 children in the 2009 report that looked at 2006 data
• 1 in 150 children in the 2007 report that looked at 2002 data
The ADDM network participating in the new report encompasses Alabama, Arizona, Arkansas, Colorado, Georgia, Maryland, Missouri, New Jersey, North Carolina, Utah and Wisconsin. The Maryland ADDM is conducted by researchers at the Johns Hopkins Bloomberg School of Public Health.
Although the overall rate is higher in the new report, some aspects of the data remain unchanged from prior years: Boys are nearly 5 times more likely to be identified with ASD than girls; white children are still more likely to be identified with ASD than black or Hispanic children; and most children with ASD are diagnosed after age 4, although ASD can be diagnosed much earlier. The data also show that Hispanic children are not evaluated as early as white or black children.
The new report, like previous reports, focuses on 8-year-olds because most ASD cases have been identified by that age. The new report also gives a more nuanced picture of who is identified with ASD. An analysis of seven of the 11 ADDM sites found that almost half of the children identified with ASD have average or above-average intellectual ability (IQ greater than 85), compared with a third of the children identified a decade ago.
ASD encompasses a wide spectrum of conditions that affect communication, social and behavioral skills. The causes are not completely understood, although studies show that both environment and genetics play an important and complex role. There is no known cure, but studies have shown that behavioral interventions, particularly those begun early in a child’s life, can greatly improve learning and skills. The CDC, which offers free checklists and information, continues to stress that parents should track their child’s development and act quickly if they have a concern.
The latest CDC report, "Prevalence of Autism Spectrum Disorder – Autism and Developmental Disabilities Monitoring Network, 11 Sites, United States, 2010," provides ASD prevalence estimates from different areas of the United States. The purpose of the report is to provide high-quality data on the extent and distribution of ASD in the U.S. population, to promote better planning for health and educational services, and to inform the further development of research on the causes, progression, and treatments.
“We continue observing increases in prevalence since the inception of the project in 2000,” said Dr. Li-Ching Lee, a psychiatric epidemiologist with the Bloomberg School’s Departments of Epidemiology and Mental Health and the principal investigator for Maryland-ADDM. “In Maryland, we found 20% of children with ASD were never diagnosed by professionals. So, we know there are more children out there and we may see the increase continue in coming years.”
“On average, children were diagnosed at age 4 years and 8 months in Maryland, even though the diagnosis of ASD can be determined as early as age 2,” Dr. Lee said. “Much work is ahead of us to catch up and close the gap.”
The data were gathered through collaboration with the Maryland State Department of Education and participating schools in Anne Arundel, Baltimore, Carroll, Cecil, Harford and Howard counties. Clinical sources such as Kennedy Krieger Institute and Mt. Washington Pediatric Hospital also took part, in addition to the Maryland Department of Health and Mental Hygne.While the report focuses on the numbers, its authors acknowledge that the reasons for the increase are not completely understood and that more research is needed. They note that the increase is likely due in part to a broadened definition of ASD, greater awareness among the public and professionals, and the way children receive services in their local communities. “It’s very difficult, if not impossible, to tease these factors apart to quantify how much each of these factors contributed to the increase,” Dr. Lee said.