Monday, October 01, 2007

Does Data Support Claim That Developmental Disabilities Will "Destroy The US"?

[ERRATA 11/24/2007: The year 2006 was mistakenly referred to as 1996 in a couple places.]

I presume most of my readers are pretty familiar with this sort of claim by now. For example, column writer Evelyn Pringle has proclaimed autism to be the "worst welfare disater in history" and further claims that "as more autistic children reach late adolescence, the need for out-of-home residential services is beginning to have a heavy impact on state budgets" (source.) When Mark Geier was interviewed by the conspiracy talk radio program Radio Liberty, he stated that if "we end up with one in six of them having brain damage, that’s fifty million Americans, we’re not going to be the number one country in the world anymore." He further suggested that "if we are not careful it’s going to destroy the United States" (source.)

These scare tactics are, of course, unsubstantiated. Note that it's not sufficient to point to the increasing administrative prevalence of autism, considering the very distinct possibility of diagnostic substitution and increasing recognition of various conditions. It's also not sufficient to point to the high costs of ABA therapy, for example, for the same reasons.

To determine if there is any merit to these claims, I think we need to look at some basic metrics, and that's what I intend to do in this post. I will use data going back to 1992 which may be requested from California DDS (CDDS). California population data is obtained from the California Department of Health Services.

Let us first look at trends in cognitive disability as a whole, by analyzing data on an aggregation of moderate, severe and profound mental retardation in the state of California as registered by CDDS. Mental retardation (MR) in CDDS is more of an assessment than a diagnosis. That is, all CDDS clients, including autistic clients, are assigned to a category such as "No MR", "Profound MR", "Unknown MR", etc. This categorization is presumably based on IQ testing. I am choosing moderate, severe and profound MR because I believe these categories would be "hard to miss" if you will, and it is unlikely that there's a recent trend of parents deciding to pursue CDDS services for these conditions where they would not have in the past. In other words, many of the caveats that would apply to the autism classification probably do not apply to these categories.

The following is a graph of the prevalence change in moderate, severe and profound MR from 1992 to 2006, as reported in July of each year.



As we can see, administrative prevalence of moderate, severe and profound mental retardation has been stable since 1992. The aggregated prevalence was 15.4/10,000 in 1992 and 15.5/10,000 in 2006.

Let us now look at a direct measure of residential costs. The following is a graph of the total number of persons, per 10,000 population, registered with CDDS, who do not live either at home (being cared for by a parent or guardian) or independently. This would include residential options such as group homes, as well as institutional care facilities, nursing facilities, etc.



As readers can see, there is actually a slight downward trend in the number of developmentally disabled persons who do not live at home or independently. The prevalence of this type of living arrangement was 10.7/10,000 in 1992 and 10.3/10,000 in 2006. I think we can all agree this is a positive trend.

Conclusion

California data does not support unsubstantiated claims by Evelyn Pringle, Mark Geier and others to the effect that "epidemics" of developmental disabilities will result in either an unmanageable fiscal burden or the destruction of the United States.

6 comments:

  1. Evelyn Pringle is not a journalist. She is a muckraker for a cabal of personal injury lawyers:
    http://www.lawyersandsettlements.com/articles.html?area=&page=53

    Even if she has moved on to other pastures, she still has the stain of doing PR for ambulance chasers.

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  2. Yes, I wasn't sure if it was appropriate to describe her as a journalist. That's why I chose "column writer".

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  3. Geier really screwed up with that quote, didn't he. We took the mercury out of vaccines and we still have 1 of 6 messed up. But, we'll still be #1 because we keep giving the full dose of thimerosal to the rest of the world. Imagine how fucked up those third world countries will be in a few years.

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  4. In a normal distribution, you will have a 1 out of 6 who are on the top part of the curve, and one out of 6 on the bottom part of the curve. It is called a "standard deviation".

    The standard deviation of 1 sigma (that looks like a un upside down Q) is where the cut off point is 16% on the upper point, and correspondingly on the lower point. See:
    http://en.wikipedia.org/wiki/Normal_distribution#Standard_deviation

    It is a point of definition. That is not a scary number, it is just basic statistics.

    Of course, the plots that are noted showing Mentally Retarded are 15 per Ten THOUSAND.... or more accurately: .15%, or 1 out of 667.

    Just like Geier and Pringle (ok, I did notice you said column writer, I just wanted to make sure folks know for WHO she writes) are using basic statistics as a scare point. And doing it badly.

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  5. These are the same people who freak out when someone tells them that half of Americans have a below average IQ, aren't they?

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  6. Do you think David Kirby could explain the statistics of the matter to Mark Geier? I suspect that would be interesting to watch.

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