Friday, February 23, 2007

On The Absurd Notion That Cognitive Disability is New

In a prior post I wrote about hysteria surrounding a "1 in 6" stat that, depending on who's promoting it, includes children with psychiatric diagnoses, or children with a number of physical illnesses such as diabetes and asthma, or simply those with brain damage. The stat is sometimes accompanied by warnings of doom for the United States.

Pretty soon they might be running around "raising awareness" of the fact that half of all children are below average, as one reader suggested.

There's an unstated assumption behind the hysteria: that children used to be completely healthy before the 1990s, or at least early in the 20th century; and that except for the relative few with some known genetic mutations, cognitively disabled children did not exist for the most part.

This, of course, is not true. But what's more, hysteria about cognitive disability is not new either. I first realized this when I saw a picture of a 1926 American Eugenics movement exhibit over at autistics.org. It reads:

Every 48 seconds a person is born in the United States who will never grow up mentally beyond that stage of a normal 8 year old boy or girl.

And then:

Every 16 seconds a person is born in the United States.

Clearly they were claiming that 1 out of 3 persons born in the United States in 1926 had a significant developmental disability. I have reasons to suspect this stat was a fabrication or an exaggeration by the American Eugenics movement. But it's not like modern organizations do not make up stats or repeat unsourced stats in order to push their agendas.

There is more reliable data out there. Let's take a 1930 study review by Raymond Barnard on the prevalence of what he calls "speech defects". He reported that careful studies at the time were giving a prevalence of about 5% to 8% of the school population.

This is completely in line with modern studies such as Silva et al. (1987), Wong et al. (1992), and Shriberg et al. (1999). (A possible caveat is that we might be doing a bit of a comparison of apples to oranges between definitions of speech impairments).

There is also some data on institutionalization from the California State Mental Hygene Survey of 1930. It tells us that there were 14,451 persons in state hospitals for the insane, with a total institutional population of 25,643. The article also gives us the population of the state in 1925: 4.2 million. So about 61 of 10,000 persons in the state were institutionalized.

I haven't found data that could be used for a fair comparison. But let's look at California DDS data from Q4 2006. The total number of CDDS clients who live either in an Institutional Care Facility or a Nursing Facility is 8,777. If we take all clients who do not live independently or with a parent, that comes to a total of 38,216 persons. That is 11.3 of 10,000 persons in the state, or about a fifth of the total institutionalized population in the late 1920s. I should note that not all or even most persons living in mental hospitals or institutions in California are necessarily registered with CDDS, but the data point is interesting nevertheless.

Those are some hard numbers I have found. If you instead prefer stories about what friends claim to remember from 20 or 30 years ago, this is definitely not the blog for you.

Thursday, February 08, 2007

Moving Toward a New Consensus Prevalence of 1% or Higher

The current consensus prevalence of ASD is roughly 1 in 166 or 60 in 10,000, as widely known. I believe this is still an underestimate.

I should clarify that I do not really believe there's a "right" number for autism prevalence. It's sort of like asking what is the prevalence of "short" or what is the prevalence of "light skinned". It depends on the boundary, and the boundary in autism is subjective. I believe it is somewhat subjective even when the best diagnostic tools are used. The standard deviation boundary of mental retardation is an analogous boundary, yet probably a more objective one.

Nevertheless, it appears that when ASD is screened thoroughly in a population, or when there's a lot of awareness and good ascertainment, prevalence is found to be closer to 1%. This is not new. The following is what Lorna Wing and David Potter said on the subject as early as 1999.

Because we concentrated on the children with learning disabilities (IQ under 70) we saw very few with the pattern described by Asperger. We had to wait for the study by Christopher Gillberg in Gothenberg to find out how many children with IQ of 70 and above were also in the autistic spectrum. As described above, combining the results of these two studies gave an overall prevalence rate for the whole autistic spectrum, including those with the most subtle manifestations, of 91 per 10,000 - nearly 1% of the general population.


And then:

Kadesjö et al (1999) report a study in Karlstad, a Swedish town. Although this was small scale it was very intensive (over 50% of the 7 year old children seen and assessed personally by the first author). The study found a prevalence for all autistic spectrum disorders for all levels of IQ, of 1.21%!!! Children were followed up four years later and had the diagnoses confirmed.

(source)

I believe Kadesjö's personal assessment of 50% of 7 year olds in Karlstad is key to that finding.

More recently, Baird et al. (2006) found a prevalence of 1.16% in South Thames, UK. In this study the authors, again, looked for children with a possibly undiagnosed ASD. Note that children in this study were born between 1990 and 1991, before the bulk of what is referred to as the "autism epidemic" got started.

Finally, we have Fombonne et al. (2006) which found a prevalence of 1.076% among Kindergarten children (born in 1998) in Montreal, Canada. While there are fluctuations in the prevalence by birth year cohort in this study, there are no indications that prevalence is about to level off just yet.

Additional supporting evidence comes from Posserud et al. (2006) out of Bergen, Norway. The authors found that 2.7% of 7-9 year olds were high scorers in the ASSQ.

In adults, prevalence of ASD can also be 1% easily considering that in studies of the properties of the AQ Test about 2-3% of adults score above 32-33, the cut-off at which an ASD is considered possible.

Saturday, February 03, 2007

Here's Where Rick Rollens Is Wrong

There has been some buzz lately about California DDS caseloads in older cohorts. See, for example, this post by Kev with graphs of caseload increase in the 62-99 and 52-61 cohorts. Interestingly, in the 1990s there wasn't just a lot of growth in the numbers of autistic little ones in the system, but autistics of all ages apparently.

JB Handley noted that the 62-99 caseload is still rather small, however, and he's right of course. Rick Rollens wrote a rant along the same lines, which follows.

I for one am really sick and tired of the current stock of "the world is flat" thinkers who continue to spew the notion that there has been no real increase in autism, that the prevalence and incidence of autism has remained the same all these years, and in years past we simply over looked thousands of persons with autism, and today we finally found them. Bottom line: they have always been here. I believe that applying a little common sense and facts provided by our California Department of Developmental Services (DDS) we can once and for all drive the spike of fact and truth into the heart of these modern day flat earth society members who may be living in our world, but seem to be far removed from it's obvious realities.

Premise : If there has not been a true, dramatic increase in the incidence of autism creating an autism epidemic, then we should have among us a proportional and sizeable number of adults with autism. Since DDS's data only includes those persons with autism who have a professional diagnoses of full syndrome (i.e. worst form) of autism, we can assume that hiding, misplacing, loosing or not recognizing thousands of adults with moderate to severe behavioral issues, extremely apparent bazaar social behaviors, and moderate to severe language deficits would be impossible. We are not talking about a person here who melds into society and is not noticed and/or is not in need of major supports and assistance. They would have to be somewhere, and somewhere for adults likes these in California would either be in the community or in an institution. Now I guess it is possible that some could be homeless, but as far as I know there has never been reports of large numbers of persons with moderate to severe autism running amok through homeless shelters and soup kitchens, if they were there, I am sure we would have heard about it by now. California's developmental services system has been in place since 1969...38 years for adults with autism and their families to find their way into the system.

Facts: According to the latest data from DDS, there are 2,809 persons with autism in California's DD system...16% or 5125 are adults over 22 years old. That means for the autism population that 84% are under the age of 22, with 78% under the age of 18. It is a remarkable fact that adults with autism make up only 16% of the autism population, while in the same DD system 55% of the cerebral palsy population, 61% of the mental retardation population, and 63% of the epilepsy population are adults over the age of 22 years old. Using an average of the CP, MR, and epilepsy populations, it is safe to assume that adults over the age of 22 with moderate to severe autism should constitute roughly 60% of the total autism population, not 16% as they do and have for many years.

So, rather then having just 5125 adults currently in our system with full syndrome autism, we should have somewhere around 19,685 adults with full syndrome autism if you believe the flat earth folks that there has been no real change in the incidence of autism. We do know that there are a very small number of adults with autism in California's five remaining state institutions... 358 to be precise. So doing the math leads me to these conclusions:

Based on the fact that roughly 60% of adults with the three other conditions served by California's DD system (MR, CP, and Epilepsy) are over the age of 22 years old, and recognizing that we have only 5125 (16%) of the autism population over the age 22, add in the 358 who currently reside in state run institutions, we are short 14,202 adults with autism in our system that should be there! That number represents 43% of the entire current autism population in California's DD system.

43% of the population missing? Over 14,000 adults in California suffering with full syndrome autism and no one has seen or heard from them? Is this possible, or is it that they simply do not or ever existed. Is it also a fact that DDS has documented, in two separate Reports, that California's autism epidemic began roughly 22 plus years
ago.

Believe me when I say....The world is round.


I think the flaw in Rick Rollens' argument is obvious: He assumes that CDDS autism counts are a good approximation of the number of autistic persons in the state of California for any age group. This is an incorrect assumption, and not just probably incorrect or a little bit incorrect. I will now provide a numerical argument as to why.

The DSM-IV-TR prevalence of PDD in the population with mental retardation is about 16% (source). This estimate appears to be conservatively valid in adults, going back at least 24 years (source).

Let's now take the mental retardation caseload in the 52-61 cohort as of Q4 2006, which is 10,632. We should thus expect that 1,701 CDDS clients have PDD with mental retardation. It seems to me that these 1,701 autistics in the 52-61 cohort could easily have an "autism" classification in their records. Instead, we find that only 325 do. CDDS has missed at least 80.9% of all autistics in that cohort. I emphasize "at least" because among young autistic clients, mental retardation is relatively rare.

This all comes to show that CDDS ascertainment is nowhere close to accurate, and it is least accurate in older cohorts. In reality all the California DDS report can give us is an approximate lower bound on ASD (not even autistic disorder).

Rick Rollens admits his argument is based on the following premise:

Since DDS's data only includes those persons with autism who have a professional diagnoses of full syndrome (i.e. worst form) of autism, we can assume that hiding, misplacing, loosing or not recognizing thousands of adults with moderate to severe behavioral issues, extremely apparent bazaar social behaviors, and moderate to severe language deficits would be impossible.


He is clearly assuming that (1) if an autistic person is not registered with CDDS, then they were "missed"; and that (2) all autistic persons registered with CDDS have "autism" in their records. Neither of these assumptions have ever been determined to be factual, which is a fatal flaw in this type of argument.

Also, Autism Diva discussed the "full syndrome" characterization. It's not really the way Rick Rollens would have us believe.

So, yeah, the world is not flat; but neither is CDDS autism ascertainment, obviously.