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Section II. Delaware Demographics

Under its remit, the Task Force was directed to develop an estimate of the number of adults with autism in the State of Delaware using available federal and state studies. To assist in this endeavor, the Task Force invited Dr. Craig Newschaffer, Professor and Chair of the Department of Epidemiology and Biostatistics at Drexel University, to consult with and assist in identifying and interpreting the relevant studies. Dr. Newschaffer is an expert in epidemiological statistics with a subspecialty of autism.i He attended the March 2007 meeting of the Task Force and testified as to the various, recognized studies of the prevalence of autism.

Newschaffer began with the well publicized study of the prevalence of autism spectrum disorders conducted by the Center for Disease Control (CDC).ii This study, released in February 2007, was a compilation of data from six states: Arizona, Georgia, Maryland, New Jersey, South Carolina, and West Virginia from 2000. The data was restricted to eight-year-olds representing approximately 4.5% of that age group in the United States at the time of the studies. The study concluded that approximately 6.7 of every 1000 children of that age had a disorder on the autism spectrum. This translates to the ratio of 1 in 150 children with autism in the United States that has become so widely publicized.

The CDC, using the Autism and Developmental Disabilities Monitoring (ADDM) network, did a follow up study from 2002 using 14 states and again, found a prevalence of autism in eight year olds of 6.6 per 1000 consistent with the 2000 review.  

Dr. Newshaffer pointed out that there are no comparable studies on adults. While these prevalence studies were designed for and conducted on children, he felt that the resulting conclusions could be reasonably applied to adults as well since autism spectrum disorders tend to be life long in duration although improvement in behavioral, social and communicative functioning is expected with appropriate services and interventions.  

As to state specific studies, Dr. Newschaffer reported on a study on autism prevalence conducted in Brick Township, New Jersey in 1989 that found a prevalence rate of 6.7 per 1000 for 10 year-olds.iii Another study conducted in the Atlanta, Georgia metropolitan area in 1996 involving three to 10 year olds found a prevalence rate of 3.4 per 1000. The CDC is currently updating these studies and expects to publish these results in the near future. He concluded that the Task Force should adopt the CDC range (1 per 150) of prevalence of its purposes and recommendations.

Finally, quite apart from the specific findings of prevalence among the various studies, Dr. Newschaffer pointed out another emerging conclusion. That is, among the other conclusions of autism studies, there is a clearly held view that the incidence of the disorder is increasing. It is his observation that the generally accepted annual rate of increase in the prevalence of autism in the United States is in the range of 29%. In response to questions from the members of the Task Force, Dr. Newschaffer said that it is not known whether this rate of increase is a reflection of a true increase in the incidence

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