Five Easy Graphs
January 28th, 2009
We still hear a lot about the “autism epidemic”. I suppose it’s only to be expected, since it is repeated so often and by so many people. And clearly, there has been an increase - a steady increase - in the number of children reported as “autistic” by educational sources and social service providers.
But is it a real epidemic?
This is a serious question because, if the rise in autism prevalence is real, then we need to find out why? Likewise, if the “autism epidemic” is an artifact of changes in awareness, diagnostic criteria, social implications, etc., then we should stop expending time, effort and - most of all - money trying to find the cause.
Here is a graph - similar to many that you may find all over the Internet - of the autism prevalence reported from 1993 (the first year “autism” was a mandated IDEA category) to 2007 (the last year USDE data is available).
Autism prevalence 1993 - 2007 (from USDE data) - click on image to enlarge
As you can see, the rise in autism - at least the USDE definition of “autism” - has been spectacular and continuous. There appears to be no slackening in the rise, no plateau in sight.
But is this an accurate view of autism?
Here is another graph. This one shows both autism and mental retardation prevalence - as reported to the USDE - over the period 1993 to 2007.
Autism and Mental Retardation prevalence 1993 - 2007 (from USDE data) - click on image to enlarge
The first thing that struck me about this graph is that autism doesn’t look so “scary”. The second is that the rise in autism coincides with a decline in mental retardation. More about that later.
The third graph shows autism and mental retardation along with all children served under the IDEA. I have not changed the autism numbers a bit.
Prevalence of Autism, Mental Retardation and All Disabilities 1993 - 2007 (from USDE data) - click on image to enlarge
Clearly, autism is not as significant a part of the total IDEA “picture” as some might imagine. You will note that over 10% of all US children are served under the IDEA.
In the next graph (number four), I have normalized the prevalence of autism and mental retardation by dividing the number of children in those categories by the total number of children served under the IDEA that year.
The reason for doing this is that the proportion of children classified under one or more IDEA disability categories has shown a slow but steady rise over the years. The possible reasons for this are many, but removing it by normalizing to the total number of children served under the IDEA eliminates one source of artificial (or administrative) drift in disability prevalence.
Autism and Mental Retardation as a percent of All Disabilities (from USDE data) - click on image to enlarge
As you can see, the prevalence of autism has shown a rise that rather closely parallels the decline in mental retardation.
Over the years, a number of people supporting the “autism epidemic” hypothesis have derisively asked those who question the “epidemic” where the “hidden hordes” of adult autistic people are. Their argument being that if autism prevalence weren’t actually rising, we should expect to find larger numbers of adults - even the elderly - with autism.
I may have found the “hidden horde”.
In the final graph (number five), I’ve added the autism and mental retardation prevalence and normalized to the total number of children served under the IDEA. This will more readily show how closely the decline in mental retardation is paralleled by the rise in autism.
Autism and Mental Retardation as a percentage of All Disabilities (from USDE data) - click on image to enlarge
As you can see, the rise in autism is almost exactly paralleled by the decline in mental retardation (slope = 0.017, r = 0.999), indicating that the total prevalence of autism and mental retardation - as a fraction of all children served under the IDEA - has not changed significantly since 1993.
Does this mean that all of the rise in autism is simply a shift away from “diagnosing” children with mental retardation? Unfortunately, these data can’t make that determination - all they can show is that the “epidemic” rise in autism has been accompanied by an…. what would you call an inverse epidemic?… an anti-epidemic of mental retardation. However, a number of studies - looking at different data sets [Shattuck (2006) and Coo et al (2007) come readily to mind] have shown that diagnostic substitution is a large part of the “autism epidemic”.
All these data show is where the “hidden horde” might have been hiding.
Of course, I don’t expect the folks who are heavily invested in the ”autism epidemic” idea to be very happy with this information. I expect that they will cast all sorts of aspersions on me, claiming that I am a “tool” of “Big Pharma” or even that I am in the pay of a sinister conspiracy of “the government”, “Big Pharma” and the “AMA”. Maybe they’ll even throw in the Rosicrucians, for good measure.
Regardless of my presence or absence on the payrolls of “Big Pharma” (or the Illuminati), I’d be interested in hearing an alternative explanation for these data that supports the idea of an “autism epidemic”.
Remember, in order to play, you have to be able to account for all of the data - you can’t just ignore the parts that don’t work for you. In addition, you can’t use large government/industrial conspiracies or aliens as part of your explanation.
Prometheus
Filed under: Autism Policy, Autism Science, Critical Thinking | 42 Comments »
Chelation: Not as safe as we’ve been told
January 2nd, 2009
Practitioners that promote the “biomedical” treatment of autism often claim that there is little risk of harming an autistic child with the interventions they recommend. “What’s the harm of trying?”, they ask; “What have you got to lose?”
As it turns out, the answer to that question may be “Quite a bit.” Apart from the cost in terms of money, time, effort and false hope, it now appears that one of the prominent “biomedical” treatments for autism may cause neurological damage.
In November, 2008, the journal Neurotoxicology released an “e-publication” of an article that casts further doubt on the efficacy and safety of chelating children with autism.
Rush T, Hjelmhaug J, Lobner D. Effects of chelators on mercury, iron, and lead neurotoxicity in cortical culture. Neurotoxicology. 2008 Nov 5. [Epub ahead of print]
In this study, the authors used primary cortical cell cultures to study the effectiveness of several chelators commonly used to treat “heavy metal poisoning”: calcium disodium ethylenediaminetetraacetate (CaNa(2)EDTA), D-penicillamine (DPA), 2,3 dimercaptopropane-1-sulfonate (DMPS), and dimercaptosuccinic acid (DMSA). All but DPA have been widely used to “treat” autistic children.
They treated the primary cortical cell cultures with four metal “toxicants”: inorganic mercury (HgCl2), methylmercury, ethylmercury (thimerosal!), lead (PbCl2) and iron (Fe-citrate) and then with one of the four chelators (and one control group that received the metals but no chelator). Their results may surprise some people.
DPA performed the worst of all, providing no protection and actually increasing the toxicity of inorganic mercury, thimerosal and iron. EDTA reduced the toxicity of inorganic mercury but “caused a severe potentiation” of iron toxicity.
Both DMPS and DMSA reduced inorganic mercury toxicity but increased the toxicity of thimerosal and iron. DMPS (but not DMSA) increased the toxicity of lead.
Now, these aren’t the results we have been led to expect. [Note: potential understatement of the year candidate]
If this had been the only study to suggest that chelation was potentially dangerous, I would be willing to shrug it off. After all, it is in cell culture, which is a questionable analogue for the intact organism. However, there have been two other studies looking at living organisms that have results consistent with the findings of Rush et al.
Dietrich et al (2004) showed that treating children with blood lead levels between 20 and 44 mcg/dl with DMSA [Note: chelation therapy with DMSA is recommended for blood lead levels of 45 mg/dl and above but not specifically recommended - or contraindicated - for blood lead levels from 10 - 44 mcg/dl] had no effect on a variety of neurocognitive tests at long-term follow-up (4 - 5 years).
However, they found a statistically significant decrease in attention and executive functions in the children treated with DMSA when compared to placebo. Given the nature of neurocognitive testing and the variation in genetic and environmental factors in humans, this result was not given a great deal of weight at the time.
In 2007, Stangle et al showed that DMSA, when given to rats that were truly lead-toxic (i.e. blood levels in the toxic range without “provocation”) improved learning and etc., but that when they gave it to rats that did not have toxic lead levels (i.e. the control group), there was a significant and sustained (i.e. permanent - it did not disappear during the duration of the study) decrease in cognitive function.
What does all this mean to parents who are - or are contemplating - chelating their autistic children? Well, it strongly suggests:
[1] Chelation with EDTA, DPA, DMPS and DMSA does not “work” for organic mercury, such as ethyl mercury from thimerosal. The Rush et al study was particularly pertinent to parents who think their children became “mercury poisoned” from thimerosal-containing vaccines, since it used thimerosal as the source of ethyl mercury.
[2] Giving DMSA or other chelators to children who do not have significant blood levels of heavy metals is likely to cause brain damage. It is probable that the chelating agents cause some degree of neurological damage, but that higher lead (or other heavy metal) levels cause sufficiently greater damage that the chelators are the “lesser of two evils”.
Many parents (and not a few practitioners) have argued, “Chelation is safe; why not give it a try? It can’t hurt and it might just help.” Well, now we have a growing body of data suggesting that chelation might not only be ineffective, it might make your child worse.
Since many practitioners following the “DAN! Protocol” or similar regimens commonly give chelating agents when (unprovoked) blood/urine levels of mercury (or other metals) are well below the toxic range, these studies are directly applicable to this practice.
An additional concern is that practitioners (and do-it-yourself parents) who chelate to “treat” autism often continue giving these drugs for years. Even the treatment of lead toxicity - which takes much longer since lead is incorporated into the bones - is usually limited to six months to a year, with careful monitoring.
People who may be tempted to smugly ignore these warnings because they are using “natural” chelating agents or other agents not mentioned in these studies should rethink their complacency. The mechanism that causes the cognitive impairments seen after DMSA treatment - and the toxicity to cell cultures seen after DPA, EDTA, DMSA and DMPS treatment - is unknown. It may well be that any heavy metal chelating agent can cause the same injury.
Prometheus
Filed under: Autism Practitioners, Autism Science, Autism Treatments | 40 Comments »