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:
Urbanicity and Autism Spectrum Disorders.
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.
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By Matt Carey
Left Brain Right Brain 
Denmark which has a Medicare for all sytem in place since WWII and every person in Denmark has their entire medical history since birth including a historyof psychiatric problems of all the citizens in a data base that is accessible to researchers around the world.. It is of considerable interest that in Denmark the prevelance rate of autism is half the prevelance rates reported in the US and other countries in western Europe and Asia (4,000 / 800,000 =0.05%). Prevelance rates in the US appear to be inflated in contrast to most accurate longitudonal records in Denmark which contains the most accurate data on the health of all its citizens.
The best epidemiologiocal research is coming out of the Scandinavian countries (Norway, Sweden and Denmark) which have the medical histories, including psychiatric illnessess of all its citizens since WWII.
Why are prevelance rates in the Scandinavian contries so much lower than anywhere else? Discuss.
“Why are prevelance rates in the Scandinavian contries so much lower than anywhere else? Discuss”
Short answer: They aren’t.
If I recall correctly, Sweden reported a prevalence of about 1.2% in the 1990s (even Andrew Wakefield quoted that study in his patent)
More to the point, Denmark has multiple studies showing ~1% prevalence. Discussion on this blog recently
From that article:
Autism after infection, febrile episodes, and antibiotic use during pregnancy: an exploratory study. 2012
Birth cohorts 1997-2003. Prevalence: 1%
Using maternally reported data to investigate the association between early childhood infection and autism spectrum disorder: the importance of data source. 2012
Birth cohorts 1997-2003. Prevalence: 1%
Parental age and autism spectrum disorders. 2012
Birth cohorts 1980-2003. Prevalence: 0.73%
I haven’t seen the full study discussed above, just the abstract. But they discuss a cohort of 800,000 kids. Consider the febrile episodes paper (http://www.ncbi.nlm.nih.gov/pubmed/23147969). For 1997-2003 they had about 97,000 kids. So, my guess is that the 800,000 number includes every autistic in the Danish register, going back decades. If so, it isn’t surprising that the overall prevalence of identified autism is lower than 1%, given the rising trend with time.
By the way, I believe you have a factor of 10 error/typo–0.5%, not 0.05%.
add the recent Stockholm Youth Cohort data–1.15% prevalence
http://www.ncbi.nlm.nih.gov/pubmed/22911770
Norway, 0.7% “At age 11 years, the incidence was 0.7% for ASD, 2.9% for ADHD, and 0.9% for epilepsy. The cumulative incidence is likely to be higher because some cases diagnosed before 2008 were probably missed.”
http://www.ncbi.nlm.nih.gov/pubmed/22711729
MoBa (Norwegian Mother/baby cohort) shows about 0.3% so far, but with little follow up time (youngest kids just about 3 years old).
http://www.ncbi.nlm.nih.gov/pubmed/23403681
So, of the three countries you presented as having the best data, the prevalence rates are about 1% in 2 and >0.7% in the third. This doesn’t sound like 0.5%, and 1/2 that of the U.S. to me. Given these data, are you prepared to modify your assertion that ” Prevelance rates in the US appear to be inflated in contrast to most accurate longitudonal records in Denmark which contains the most accurate data on the health of all its citizens.”?
“Yes, a larger fraction of kids in rural areas are identified as autistic–even if they were born in a rural area.”
Is there a typo in this sentence? Shouldn’t it read “Yes, a larger fraction of kids in URBAN areas…..”
Yes–that would be my error! Thanks for catching it.
Glad to help
I am involved in community action against a project which will involve many years of heavy construction activity 24/7. . . in researching harmful impact, we found that foetal exposure to constant (or even intermittent) loud noises leads to changes in the very architecture of the brain. Children respond by learning to tune-out… I was struck by the similarity to symptoms ascribed to ASD. (Sorry, citations are not readily available, but I have to dig them out for an injunction, so if you want them I’ll provide. Basic stuff, though – as I recall NIH has “everyman” articles available). In urban areas normal background noise levels are ca. 80 dB – with frequent spikes. Things become messy (anyone want to do a study?) when trying to figure out if symptoms ascribed to ASD s/b ED, or vice versa. Until we get a reliable etiology it might be safer to talk about symptoms, not overall diagnosis
Sullivan:
Are autism prevelance rates inflated, yes. Widening of diagnostic criteria and diagnostic substitution is largely to blame. Can a genetic epidemic exist, yes, at least in part.
I have covered the origins of de novo gene mutations and the heritability of autism in two articles just published in a new autism journal (OA-Autism). The editor-in-chief is Dr. Manuel Casanova and the editorial board is well represented by researchers who have been on editorial boards of the major print autism journals and with Autism Speaks including Margaret Bauman and Ira Cohen and a number of researchers from the MIND Institute and the NIH. This new journal has accepted submissions for just two months and will not be eligible for abstracting to PubMed until after a year has past. The mission statement is to encourage debate and argument and challenge the dogma of behavioral genetics and molecular genetics who have dominated the field of autism for six decades. Both of these articles were invited by the editor-in-chief and therefore Open Access publication fees were waived. These articles can be viewed at :
http://www.oapublishinglondon.com/oa-autism
You dodged the question.
You relied upon data from certain countries to support your belief. Those data actually go against your belief. That doesn’t really work to convince me that my time is well spent reading your articles. I wish you well with your efforts.
Oh–and I forgot to add another Danish study (discussed here on LBRB and also recently re-appearing in Pubmed)
The best epidemiological work comes out of countries like Denmark, per your previous comment, correct?
I recall previous to the California Twin Study, you were unaware of the other recent twin studies (one from Berman’s group at Columbia and one from the Gernsbacher group at U. Wisconsin. You are welcome to “challenge dogma”, but if you are not aware of studies which go against your beliefs, you run the risk of being accused of being dogmatic yourself.
From discussions on this site, I found that one of the editors of this new journal was also unaware of recent studies in areas she was commenting upon (autism and vaccines). But she was quite willing to challenge the “dogma” as you put it surrounding the question. It was not an impressive discussion on her part.
One other possibility: life in rural areas tends to be (or tended to be more so in the past) more routine than life in urban areas and involves less interaction with “new” people. Under those circumstances, “high functioning” autism might not “stand out” as much as it would in places where there are more disruptions of routine and novel interactions, and thus might be less frequently seen as problematic (sort of similar to the way some ASDs aren’t really noticed until a kid moves from elementary school to middle school where they have to “shift their mental gears” more frequently). In the absence of universal screening, this would lead to a smaller percentage of autistic kids (mostly the more “severe” ones) being brought to a professional for evaluation.
Interestingly, in Gary Paulsen’s novel Harris and Me which is about a city kid’s summer on a farm, one member of the farm household is quite clearly autistic (in fact, non-verbal) but nobody sees him as all that unusual; he simply has a well-defined role that he fits into well.
One thing to look for would be a pattern where diagnosed autistics who grew up in rural areas were diagnosed at a later age than those who grew up in urban areas. This would be consistent with both my suggestion and the “poorer services” hypothesis, but not very consistent with the idea of differential causation due to early-childhood or prenatal environment.
I was unable to read the full paper but I was wondering if they controlled for the fact that some people would their kids from rural areas for ASD services?
Sorry I didn’t seem to see this earlier.
There seems to be a word or phrase missing here
“In my own school district, for example, the administrative prevalence of autism is 1/3 that of Caucasians.”
Now, because you and I have spoken about this several times, I’m guessing I know what word or phrase is missing.
But other readers may not.