On May 5 the Centers for Disease Control and Prevention (CDC) published the findings from two new surveys reporting the prevalence of autism among children ages 4-17 between 2003 and 2004. Although CDC has previously conducted population surveys of specific geographical regions, the new surveys provide
the first nationally representative estimate of autism prevalence in this age group. The National Health Interview Survey (NHIS) reported autism prevalence as 5.7 in 1000, or 1 in 175, and the National Survey of Children's Health (NSCH) reported a prevalence rate of 5.5 in 1000 or 1 in 181. These prevalence rates are consistent with the highest end of the previously reported range of 1 in 500 to 1 in 166. Taken together, and extrapolating to the total number of children in the US between the ages of 4 and 17, the surveys would indicate that between 2003 and 2004, more than 300,000 children had an autism diagnosis. Cure Autism Now is collaborating with CDC to further capture epidemiological data and research susceptibility.
For these new large-scale surveys the prevalence rate was based upon parental report of a diagnosis of autism. Parents were specifically asked if they had ever been informed by a healthcare provider that their child had autism. In both surveys, parents who reported that their children had an autism diagnosis also reported that their children exhibited emotional, developmental or behavioral problems associated with autism (such as peer problems and hyperactivity). These children were also more likely to be described as having special healthcare needs and requiring medical, mental health or educational services.
In CDC's telebriefing, epidemiologist and study author Dr. Laura Schieve conceded that the survey methods have two major limitations, both of which may result in a potential underestimation of the parentally-reported autism prevalence. The first is that parents needed to have access to healthcare in order to receive a diagnosis, potentially biasing the results as healthcare access is expected to be dependent on socio-economic status. The second limitation is that the survey only asked about autism, leading to potential underreporting by parents of children with other disorders on the autism spectrum such as Asperger's Syndrome or Pervasive Developmental Disorder (PDD). Nonetheless, both surveys had consistently similar findings, and parental reports of emotional, medical and behavioral issues were consistent with parental reports of an autism diagnosis.
Despite the technical limitations, the new findings are significant because they further support the current range of prevalence rates using a different method and with a nationally representative sample. Dr. José Cordero, Director of CDC's National Center on Birth Defects and Developmental Disabilities stated in the telebriefing that when considered with previous studies, these survey results strongly reiterate that “autism is a condition of major public health concern and affects many families.” Although the surveys do report the number of children with autism by age range, they do not address time trends in autism. However, later this year CDC will be releasing an update on the Metropolitan Atlanta Developmental Disabilities Surveillance Program (MADDSP) study which will compare the prevalence rates for 8-year-olds in Atlanta for 1996 and for 2000. In addition, CDC will be reporting the prevalence findings from six monitoring sites from the Autism and Developmental Disabilities Monitoring (ADDM) Network for the year of 2000. Furthermore, Dr. Cordero reported that next year they expect to be able to update the results of the ADDM network by reporting the findings from the year 2002 for a total of 14 sites in the ADDM network.
To support these epidemiological efforts, Cure Autism Now (CAN) is collaborating with CDC to provide logistical assistance for their Centers of Excellence for Autism and Developmental Disabilities Research and Epidemiology (CADDRE) sites. CAN is providing CADDRE with its Internet System for Assessing Autistic Children (ISAAC), which is a Web-based system developed by CAN for large-scale phenotypic data collection and data management. Additionally, in collaboration with CAN's Autism Genetic Resource Exchange (AGRE) and Stanford University, CDC is conducting prevalence studies that include multiplex families that will provide additional information on susceptibility and sibling recurrences.
To read more on CDC's national autism survey results,on CDC's Web site.
Reference: Schieve, L.A., Rice, C., Boyle, C., Visser, S.N., Blumberg, S.J. (May 5, 2006). MMWR 55 (17). pp. 481-486.