The CDC last week published an updated report on autism prevalence in the United States, “Prevalence of Autism Spectrum Disorders — Autism and Developmental Disabilities Monitoring Network, 14 Sites, United States, 2008” (Surveillance Summaries, March 30, 2012 / 61(SS03);1-19). Widely reported in the media were the highlights:
· Autism prevalence for all children in study: 1 in 88
· For boys: 1 in 54
· For girls: 1 in 252
· Average age of autism diagnosis is 4 years old
· 23% increase in prevalence from 2006 data to 2008 data
78% increase in prevalence from 2002 data to 2008 data
These are staggering numbers. Let’s carefully examine actual report to understand what they truly mean. I’ve highlighted aspects of the study abstract and commented below.
Problem/Condition: Autism spectrum disorders (ASDs) are a group of developmental disabilities characterized by impairments in social interaction and communication and by restricted, repetitive, and stereotyped patterns of behavior.
Autism is defined by DSM-IV-TR standard criteria, the same as has been used for the 2002 and 2006 CDC studies.
Period Covered: 2008.
Data was collected in 2008. There is typically a several-year lag in reporting. Keep in mind we are discussing prevalence rates from 2008, published in 2012.
Description of System: The Autism and Developmental Disabilities Monitoring (ADDM) Network is an active surveillance system that estimates the prevalence of ASDs and describes other characteristics among children aged 8 years whose parents or guardians reside within 14 ADDM sites in the United States.
A child is included as meeting the surveillance case definition for an ASD if he or she displays behaviors (as described on a comprehensive evaluation completed by a qualified professional) consistent with the American Psychiatric Association's Diagnostic and Statistical Manual-IV, Text Revision (DSM-IV-TR) diagnostic criteria for any of the following conditions: Autistic Disorder; Pervasive Developmental Disorder–Not Otherwise Specified (PDD-NOS, including Atypical Autism); or Asperger Disorder.
The ADDM consists of 14 CDC-funded sites (Alabama, Arizona, Arkansas, Colorado, Florida, Maryland, Missouri, New Jersey, North Carolina, Pennsylvania, South Carolina, Utah, West Virginia, and Wisconsin) throughout the country. These sites are supposedly representative of the entire country’s population but of course there are limitations in this assumption. Each site is responsible for evaluating chart data from doctor’s offices, hospitals, and (in some states) school educational files. “Trained clinicians” review the charts and determine if, based on what is written, a child meets DSM-IV-TR criteria for ASD. Charts are evaluated for children from birth through age 8 at the time of review (in 2008). Therefore, these children today are 4-12 years old.
Results: For 2008, the overall estimated prevalence of ASDs among the 14 ADDM sites was 11.3 per 1,000 (one in 88) children aged 8 years who were living in these communities during 2008. Overall ASD prevalence estimates varied widely across all sites (range: 4.8–21.2 per 1,000 children aged 8 years). ASD prevalence estimates also varied widely by sex and by racial/ethnic group. Approximately one in 54 boys and one in 252 girls living in the ADDM Network communities were identified as having ASDs.
Comparison of 2008 findings with those for earlier surveillance years indicated an increase in estimated ASD prevalence of 23% when the 2008 data were compared with the data for 2006 (from 9.0 per 1,000 children aged 8 years in 2006 to 11.0 in 2008 for the 11 sites that provided data for both surveillance years) and an estimated increase of 78% when the 2008 data were compared with the data for 2002 (from 6.4 per 1,000 children aged 8 years in 2002 to 11.4 in 2008 for the 13 sites that provided data for both surveillance years).
While the overall rate of 1/88 children is certainly cause for alarm, some states – including New Jersey – report much higher rates. In New Jersey, 1/49 children were diagnosed with ASDs including a whopping 1/29 boys. Utah was the only state with a higher prevalence rate. Remember, this is among the 14 sites, not among 50 states. Also note that prevalence is defined as the number of all cases of children with autism in 2008 divided by the total study population. They may have been diagnosed at any time from birth until 2008. This is different than incidence – the number of new cases during the study period. The rates of increase, whatever the reason, are incredible. In two years of surveillance, at the same sites using the same methodology – WITH NO CHANGE IN CRITERIA FOR DIAGNOSIS – there was a 23% jump. In 6 years, the increase was 78%.
Interpretation: These data confirm that the estimated prevalence of ASDs identified in the ADDM network surveillance populations continues to increase. The extent to which these increases reflect better case ascertainment as a result of increases in awareness and access to services or true increases in prevalence of ASD symptoms is not known. ASDs continue to be an important public health concern in the United States, underscoring the need for continued resources to identify potential risk factors and to provide essential supports for persons with ASDs and their families.
I’ve included the entire interpretation here for good measure. I agree with most of it except the continued emphasis on “increases in awareness.” Really, was there any major increased emphasis from 2006 to 2008? There certainly was no change in case definition from 2002 to 2006 to 2008. When does that stop becoming an excuse to look at other factors contributing to the prevalence increase? I do believe certain sites have higher rates than others based on “access to services.” Families move to NJ regularly because we have relatively good educational and health services for children with autism. More detailed questions about the reasons for increased prevalence need to be asked and answered.
Public Health Action: Given substantial increases in ASD prevalence estimates over a relatively short period, overall and within various subgroups of the population, continued monitoring is needed to quantify and understand these patterns. With 5 biennial surveillance years completed in the past decade, the ADDM Network continues to monitor prevalence and characteristics of ASDs and other developmental disabilities for the 2010 surveillance year. Further work is needed to evaluate multiple factors contributing to increases in estimated ASD prevalence over time.
I know it’s hard to read emotion in a written report, but there seems to be no explicit urgency stated here. When will the CDC finally declare autism is epidemic in the U.S.? Merriam-Webster defines epidemic as “affecting or tending to affect a disproportionately large number of individuals within a population, community, or region at the same time.”
Is it not evident that autism, no matter what you believe the causes are, affects a disproportionately large number of children in our society today? Urgent work is needed to figure out not just what is happening (i.e. the true prevalence numbers) but why – and how to reverse the trend.
Lawrence D. Rosen, MD is a board-certified general pediatrician committed to family-centered, holistic child health care. He practices primary care at the Whole Child Center in Oradell, NJ and consults at the Joseph M. Sanzari Children's Hospital at Hackensack University Medical Center, serving as Medical Advisor to the Deirdre Imus Environmental Center for Pediatric Oncology.
Dr. Rosen is an internationally recognized expert in Pediatric Integrative Medicine. He is a founding member and Chair of the American Academy of Pediatrics Section on Integrative Medicine. Dr. Rosen is appointed as Clinical Assistant Professor in Pediatrics at New Jersey Medical School. He is a graduate of New York Medical College and the Massachusetts Institute of Technology, and he completed his residency and chief residency in pediatrics at Mount Sinai Hospital in New York.
Dr. Rosen is a contributing author/editor for several books, including “Integrative Pediatrics” (Oxford University Press 2009), “Green Baby" (DK 2008), and "Pediatric Clinics of North America: Complementary and Alternative Medicine" (Elsevier 2007). He is a contributing editor and pediatric columnist for Kiwi magazine.