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Autism is more prevalent in urban areas

Posted Jul 01 2013 2:00am

When my kid was first diagnosed autistic I was presented with the idea of the “autism epidemic”. There was a great deal of discussion at that time about the rising number of clients in the California Department of Developmental Services (CDDS) system receiving services for autism. One of the first thing I did was to search through another database in California–that of the California Department of Education. What I learned quickly was that autism is not identified at the same rate for various locations or various racial/ethnic groups. The disparities are quite large. In my own school district, for example, the administrative prevalence of autism is 1/3 that of Caucasians. This has remained constant over the past 10 years, even as the overall numbers increase. Another disparity that has been observed repeatedly is a disparity between cities (urban) and rural areas. The fraction of autistics identified in urban areas is higher than that in non urban areas.

Recently, a study of the Danish population finds that, yes, the more urban area a kid lives in, the higher the chances are that s/he will be diagnosed autistic:

The etiology of autism spectrum disorders (ASD) is for the majority of cases unknown and more studies of risk factors are needed. Geographic variation in ASD occurrence has been observed, and urban residence has been suggested to serve as a proxy for etiologic and identification factors in ASD. We examined the association between urbanicity level and ASD at birth and during childhood. The study used a Danish register-based cohort of more than 800,000 children of which nearly 4,000 children were diagnosed with ASD. We found a dose-response association with greater level of urbanicity and risk of ASD. This association was found for residence at birth as well as residence during childhood. Further, we found an increased risk of ASD in children who moved to a higher level of urbanicity after birth. Also, earlier age of ASD diagnosis in urban areas was observed. While we could not directly examine the specific reasons behind these associations, our results demonstrating particularly strong associations between ASD diagnosis and post-birth migration suggest the influence of identification-related factors such as access to services might have a substantive role on the ASD differentials we observed.

Let’s repeat that last line for emphasis: “our results demonstrating particularly strong associations between ASD diagnosis and post-birth migration suggest the influence of identification-related factors such as access to services might have a substantive role on the ASD differentials we observed.”

Yes, a larger fraction of kids in rural urban areas are identified as autistic–even if they were born in a rural area.

While many will see this as a threat to the idea that there is a vaccine-induced epidemic of autism. After all, if we aren’t identifying all the autistics in a given population, how can one take services related data and claim that the true rate of autism is rising? While there is some small value in putting yet another nail into that coffin lid, the real value of a study like this is pointing out that there is likely a substantial population left unidentified. Even today. Those not identified as autistic are either (a) identified as having some other disability or (b) not identified as disabled at all. In other words, there is likely a large population who are not receiving the services and supports which are best suited to their needs. That’s real. That’s wrong. And we need more people advocating to correct it.


By Matt Carey


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