What does the MIND study on autism prevalence really say?
Abstract: Background: Autism prevalence in California, based on individuals eligible for state-funded services, rose throughout the 1990s. The extent to which this trend is explained by changes in age at diagnosis or inclusion of milder cases has not been previously evaluated.I know you will correct me if I'm wrong in my interpretation of this abstract, but it seems to me that the media has been far off the mark. Here are the points that I believe to be particularly significant:Methods: Autism cases were identified from 1990 through 2006 in databases of the California Department of Developmental Services, which coordinates services for individuals with specific developmental disorders. The main outcomes were population incident cases younger than age 10 years for each quarter, cumulative incidence by age and birth year, age-specific incidence rates stratified by birth year, and proportions of diagnoses by age across birth years.
Results: Autism incidence in children rose throughout the period. Cumulative incidence to 5 years of age per 10,000 births rose consistently from 6.2 for 1990 births to 42.5 for 2001 births. Age-specific incidence rates increased most steeply for 2- and 3-year olds. The proportion diagnosed by age 5 years increased only slightly, from 54% for 1990 births to 61% for 1996 births. Changing age at diagnosis can explain a 12% increase, and inclusion of milder cases, a 56% increase.
Conclusions: Autism incidence in California shows no sign yet of plateauing. Younger ages at diagnosis, differential migration, changes in diagnostic criteria, and inclusion of milder cases do not fully explain the observed increases. Other artifacts have yet to be quantified, and as a result, the extent to which the continued rise represents a true increase in the occurrence of autism remains unclear.
- While changes in diagnostic criteria and related issues may not explain the entire rise is autism diagnoses, they do explain no less than 68% of the increase. I'm no mathematician, but if at least 68% percent of the increase is explainable as a result of changes NOT related to increased incidence of autism, then only 32% of the increase has yet to be explained. That seems to me to be a very significant finding.
- The conclusion of this study is NOT "autism is on the rise as the result of environmental factors," but rather "the extent to which the continued rise represents a true increase in the occurrence of autism remains unclear." This statement is in direct contradiction to both the headlines and the contents of most recent articles.
- Contrary to what was stated in many major articles (which variously say that the researchers included data from census and other sources), the research was based SOLELY on "Autism cases... identified from 1990 through 2006 in databases of the California Department of Developmental Services." Since the Department of Developmental Services has stringent guidelines about which individuals they'll serve (they serve only those individuals with "significant" limitations), it's reasonable to believe that the study was somewhat skewed toward counting more severely impacted children with autism.
Comments
Have you ever seen Al Gore’s documentary “An Inconvenient Truth”? As a mom of a six year old with a ASD diagnosis it is my opinion that the rise in autism is every parent’s ‘Inconvenient Truth’. It is clear to me that the rise in toxins in our environment is a huge factor in our children’s development. It is our responsisbility as parents to join together and protect the children of today and tomorrow. How can we not want to find out the truth about toxic metals, pesticides and things that are harming our children and our world!!??
Karen – I absolutely agree that we should be investigating environmental triggers of autism. I’m not sure, though, that this particular study is much help along those lines (except insofar as the media has hyped its findings far beyond what’s actually been discovered).
Personally, I would love to see studies that actually select kids with particular symptoms, and look for common threads that might explain the causes of those symptoms. For example, there seems to be a group of children with autism who ALSO have GI issues (constipation, diahhrea, reflux). Is there a causal connection, or is it just coincidence? We still don’t know!
The same goes for children with autism who have (or don’t have) severe sensory issues; epilepsy; sleep disorders; etc. We don’t know whether those symptoms are truly related to autism, whether there’s a causal connection, or why those symptoms occur.
And what about the 38% of children whose diagnoses can’t be accounted for based on changes in diagnostic procedures, etc.? Who ARE those kids? What do they have in common?
Best,
Lisa (autism guide)
I believe the percentages you quoted are a little confusing. I don’t have access to the full article, either, but my understanding is that the autism rate (per 10,000) in California has increased 585% (42.5 – 6.2)/6.2 over the time period covering 1990 to 2001. The abstract does not state that earlier diagosis accounts for 12% of the total increase nor that inclusion of milder cases accounts for 56% of the total increase. It states that a 12% increase appears to be the result of earlier diagnosis and a 56% increase appears to be the result of inlusion of milder cases. That leaves a 548% (585 – 12 – 56 = 548) increase in the rate of autism that is not statistically explained by earlier diagnosis and inclusion of milder cases combined.
Correction on my math in prior post. (585 – 12 – 56 = 517). Same order of magnitude but I mistyped the numbers while my autistic son was on my lap.
I believe your math is wrong also. Neurologist Steven Novella, who took the time to read the study before starting critical 3 blog entries, states in his blog “So in total they could explain only about a 68% increase in autism diagnosis, which is about 10% of the total increase. “.
There also been some confusion over the study vs the UC Davis press release, which states “Published in the January 2009 issue of the journal Epidemiology, results from the study also suggest that research should shift from genetics to the host of chemicals and infectious microbes in the environment that are likely at the root of changes in the neurodevelopment of California’s children. “. The media has chosen to write on the plain language of a press release vs the actual study, which if I had to bet is what happens with virtually every study ever reported on.
This is a what’s left kind of study that eliminates a large region of speculation in the dismissal of a true autism epidemic. Congratulations to those who can sit around and list problems with this study, but the burden of proof now rests with you to prove there is not an epidemic. Nobody denies a rise in the numbers. You need to do more than speculate about the 90% unexplained portion. Its time to re-evaluate the merit of spending 10-20 times more on genetic research vs environmental research.
[Congratulations to those who can sit around and list problems with this study, but the burden of proof now rests with you to prove there is not an epidemic. Nobody denies a rise in the numbers. You need to do more than speculate about the 90% unexplained portion.]
This is an excellent demonstration the misunderstanding of what “epidemic” is, as well as misunderstanding of scientific burden of proof.
“Epidemic” is a situation where prevalence would exceed the epidemiological predictions for prevalence. That doesn’t happen in either the CDDS data or the IDEA data. “Epidemic” is a notion not addressed by this study.
There is no burden of proof for the non-existence of an epidemic, because that’s not the claim. The actual scientific version of the perspective is that there is no evidence of an autism epidemic. There might be an epidemic (it is possible), and all that’s needed to support this is scientific evidence of its truth from those who claim there is. This study likely provides no information in this regard, nor was it designed to.
There’s nothing in the abstract that suggests to me that the percentages relate to anything larger than the usual 100%. Obviously, I could be wrong – but I’d need more info to be absolutely certain.
As regards the issue of epidemic-or-not, I honestly think the jury is still out.
What I would say is that I am morally certain that at least a large percentage of the increase in diagnoses are due to “artifacts” such as expanded diagnostic criteria; new educational programs and laws; increased awareness; and so forth.
If one really does remove all of those elements, the number that is left may or may not represent a true “epidemic.”
It seems to me, though, that separating out those individuals whose diagnoses are NOT due to “artifacts” would be extremely helpful. By looking closely at those individuals whose diagnoses are NOT due to “artifacts,” we may be able to better understand what autism IS, to what degree its incidence has increased, and what people with autism diagnoses really do have in common relative to possible causal factors.
Lisa (autism guide)
There is no burden of proof in establishing the fact of an autism epidemic, only in assigning a cause. Nobody is on trial here in this foundational question – not vaccine makers, not the coal fired plants, not the household chemical industry, not the deer ticks, or even ultrasound makers, neither are the geeky mom’s and dads, the CDC, or the pediatricians. Some absurd definitions won’t call anything an epidemic unless it involves infectious disease. Choose your own definition and call it what you want, but a problem with a 700% rise since 1990 (and rising still), with 90% unexplained by technicalities is not a genetic centered problem unless the end of humanity is near and it is most definitely not static. There will be a lack of clarity in the rates of mild forms of autism, but there is no such lack of clarity in the rise of the severe forms.
There is abundant specific and non specific evidence of environmental factors in autism besides this study:
1.A COMPLETE VOID in family histories of anything resembling the autism disability that is appearing today. In one particular sample(mine) you have a generation of 92 great grandchildren seeing an autism rate of 1:10 for boys representing 3 of 4 of the great grandparents children, with no known or suspected autism in any other generation. Isolated mild autistic traits that have always been around are not the same thing as autism the disability that is separating society into two groups at an alarming pace
2.Identical twin studies do not support a genetics only model. A less than 100% rate in the second twin tends to discredit the genetic only theory.
3.Wide variations in autism rates by state – from 1:88 in Minnesota to 1:432 in New Mexico
4.The rain study, goofy as it may sound, if nothing else showed that autism rates are not static across adjacent regions. How on earth we all bought a uniform 1:150 rate I’ll never know.
5. Regressive autism – kids born with the genetic ability to develop language who lose it
6.The lack of a need for a diagnosis prior to 1943. Many very obscure conditions were well defined hundreds of years earlier.
7.The Hannah Polling case, which amongst other things showed that having a neurologist father and attorney mother can help cut through the BS claims of ubiquitous vaccine safety in the “autism like” symptom vaccine related injury debate.
8.“Proximity to point sources of environmental mercury release as a predictor of autism prevalence” by R. Palmer, S. Blanchard and R. Wood
9.Autism rates of 1:28 Somali immigrants in Minnesota school systems
10.Room 5 – Northvale NJ 2007 autism rate of 3:39 amongst children of people who worked in the room – A more dramatic account states “A task force found that children born to staffers who once worked at St. Anthony’s on Walnut Street had a higher percentage of autism. 57 percent were diagnosed with neurodevelopmental disorders, 24 percent, or 1 in 4, were diagnosed with autism”. In 1999 a cluster was reported in Brick NJ.
11.Valporate (Depakote) – which has been shown to induce autism at a rate 7 times higher than with mothers on other epilepsy medication( Autism Spectrum Disorders Following In Utero Exposure to Antiepileptic Dugs
Bromley et al. Neurology.2008 )
12.Rubella-susceptible pregnant women exposed to rubella have a 1:24 chance of having an autistic child (see 1964 Rubella outbreak and “Autism in children with congenital rubella” – Journal of Autism and Developmental Disorders )
Did we we need this study to tell us environment plays a key role in the rise of severe autism? I don’t think so. Some people are just determined to make this exercise in the obvious as difficult as possible. Genetic markers may be the low hanging fruit in the equation, but ultimately they are not likely to play a key role in change, especially if expensive testing is required of two parents to develop a probability matrix of autism traits in offspring. The more practical developments will come from making the environment safer for all.
The study offers what they found causes were not related to but really offered not what the causes could be. That is still open for interpretations, observation and speculations.
There is no burden of proof in establishing the fact of an autism epidemic, only in assigning a cause.
There is no burden of proof in establishing the fact that moon is made of green cheese, only in determining its origin.
Some absurd definitions won’t call anything an epidemic unless it involves infectious disease.
Such a definition was not suggested.
Choose your own definition and call it what you want, but a problem with a 700% rise since 1990 (and rising still), with 90% unexplained by technicalities is not a genetic centered problem unless the end of humanity is near and it is most definitely not static.
What percentage is not explained by increased awareness and recognition? Please be precise.
What percentage is not explained by diagnostic substitution?
How has this reported “increase” contributed to an increase in the proportion of students in special education (as a percentage of the population) in California?
I’m open to the idea that there has been a real increase in California, I just want to know what evidence you have that it is real. After all, even the study concluded:
Autism incidence in California shows no sign yet of plateauing. Younger ages at diagnosis, differential migration, changesin diagnostic criteria, and inclusion of milder cases do not fully explain the observed increases. Other artifacts have yet to be quantified, and as a result, the extent to which the continued rise represents a true increase in the occurrence of autism remains unclear.
As regards the issue of epidemic-or-not, I honestly think the jury is still out.
Honestly? Which jury is that? What evidence do you have that the rise in diagnoses is due to anything more than a combination of expanded criteria, diagnostic substitution, greater awareness, expanded services, and other social factors? Like DoC said, the burden of proof is on the person making the claim of an epidemic. If you’re honest, that is.