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Professor Peter Bearman on vaccines and autism revisited

21 Apr

I’ve posted a few pieces on the work of Prof. Peter Bearman recently. I mentioned his work on vaccines and autism in one post but the lecture was not one that could be embedded and the part on vaccines is only a relatively short bit towards the end of the lecture.

So I took that section of the lecture out and put it on YouTube so I could embed it. This is discussing data from what I assume is an upcoming paper by Prof. Bearman’s group.

Prof. Bearman notes that vaccine refusal rates in California are higher in areas where autism organizations have a presence. However, vaccine refusal rates are *not* higher in areas with high autism prevalence.

In other words: autism isn’t scaring people away from vaccination. But, autism organizations are.

can be as much as 7 times higher if there are autism organizations in a given area. The baseline refusal rate in California is about 1.6% (in 2003). In other words, there are pockets of vaccine refusal of 10% or more in California, correlated with autism organization presence.

There are those who gloat about increasing fear of vaccines. It is too bad that time, money and effort didn’t go into something valuable to the autism communities. Let’s hope it doesn’t backfire on us in the form of infectious disease outbreaks blamed on the autism community.

Prof. Peter Bearman interviewd by Tom Insel

21 Apr

Prof. Peter Bearman is a sociologist at Columbia University who has undertaken a monumental task: figure out what is behind the increase in autism prevalence. He has chosen (at least so far) to work with California Department of Developmental Services data. This dataset is no where near the “gold standard of autism epidemiological data” that some have touted it to be. But it remains as one of, if not the best, dataset in the US.

I wrote about his most recent paper in Social influences on the rise in autism prevalence and Diagnostic change and the increased prevalence of autism.

Given the importance of this work, I thought it worthwhile to present this short interview of Prof. Bearman by the NIMH Director and IACC chair, Dr. Tom Insel. It is significantly shorter than the full lecture I linked to, and it is possible to embed it:

Prof. Bearman’s team is working on analyzing the California Department of Developmental Services (CDDS) dataset to see what trends can be identified.

Ascertainment, change in diagnostic criteria, increases in parental age, socio-demographic changes are factors in the increase in prevalence.

For example, in the past, it was wealthy families who were more likely to obtain an autism diagnosis for their child. Now that socio-economic divide is disappearing. This is a sign that ascertainment has been an effect.

Professor Bearman notes that some effects have been quantified:

25% of the increase is diagnostic change on the border between autism and mental retardation
16% of the increase is diagnostic change on the other border–between autism and other disorders
3% spacial clustering
11% increased parental age

Prof. Bearman suggests that the increased parental age factor is likely genetic in origin. Increased parental age leads to more copy number variations (CNV), leading to more autism.

I don’t expect this to change the “there can’t be a genetic epidemic” slogan. At this point it isn’t proven that this large factor is genetic. But it is possible.

There is still a large fraction of the increase which is unaccounted for. Prof. Bearman warns at the end that a search for a “quick and dirty” answer may not be advancing science.

I take “quick and dirty answer” to mean vaccines.

The problem is highly complex. The next steps in this study will be very difficult. The social influences on increasing autism prevalence can amplify other factors. Finding possible causes for a real increase in autism incidence will be complicated by other factors. But unless someone quantifies and understands those factors, the likelihood is very low of ever finding causes of autism which might drive part of the increase in prevalence.

Shocking news from Danish autism epidemiolgists!

18 Mar

Danish epidemiolgists have looked at criminal behavior in autistics, and the results are nothing short of startling:

In their paper, Pervasive developmental disorders and criminal behaviour: A case control study, authors S.E. Mouridsen, B. Rich, T. Isager, and N.J. Nedergaard, show:

The prevalence and pattern of criminal behaviour in a population of 313 former child psychiatric in-patients with pervasive developmental disorders were studied. The patients were divided into three subgroups and compared with 933 matched controls from the general population. Age at follow-up was between 25 years and 59 years. An account of convictions in the nationwide Danish Register of Criminality was used as a measure of criminal behaviour. Among 113 cases with childhood autism,.9% had been convicted. In atypical autism (n = 86) and Asperger’s syndrome (n = 114) the percentages were 8.1% and 18.4%, respectively. The corresponding rate of convictions in the comparison groups was 18.9%, 14.7%, and 19.6% respectively. Particular attention is given to arson in Asperger’s syndrome (p =.0009). © 2008 Sage Publications.

Yes, autsitics are as much as 20 times less likely to be convicted of crimes as their “typical” counterparts (0.9% compared to 18.9%).

I ran across this abstract and, given the current hype over Danish epidemiologists I couldn’t resist presenting it in this sensational mode. Besides, the title may draw some readers from the contingent bent on portraying child autistics as a looming threat to the well being of society.

Autism-study doctor facing grant probe

13 Mar

A story in the Philadelphia Inquirer today sheds some light on the situation involving Dr. Poul Thorsen.

Background for anyone who needs it: Dr. Thorsen is a Danish researcher who is co-author on a number of important studies. These include epidemiological studies on vaccines and autism. Dr. Thorsen did this work at the University of Aarhus, and has since left. There is an investigation ongoing apparently implicating Dr. Thorsen in a possible shortfall of about US$2M from the University.

Dr. Thorsen’s work was funded largely by the CDC. He started working for Emory University before leaving Aarhus (and this is a point of contention with Aarhus, as they state that Dr. Thorsen was not allowed a joint full-time appointment). He was also listed as adjunct faculty at Drexel University. Dr. Thorsen has also left Emory and his adjunct appointment at Drexel.

There has been a lot of speculation and discussion on this for the past week or so. The story has broken into the mainstream media, who have been good enough to get us some facts to work with. I have sent many emails over the past week, and almost all have been unanswered. I finally heard from one group in Denmark yesterday, and they to are unaware of the details of this case.

Today’s Philadelphia Inquirer has a story about Dr. Thorsen, Autism-study doctor facing grant probe by Jeff Goldstein:

A Danish scientist involved in two major studies that debunked any linkage of vaccines to autism is suspected of misappropriating $2 million in U.S. grants at his university in Denmark.

He also notes that Dr. Thorsen’s appointment at Drexler was unpaid, and he resigned it this week. (Drexel University is local to Philadelphia, where Mr. Goldstein works). Also of note, Dr. Thorsen was working with Emory University for about 6 years, much of that part time. The complaint by Aarhus involves him working “full time” in both Aarhus and Emory. This may go to the fact that it was pretty clear that Dr. Thorsen was at both Emory and Aarhus from his publication record. The complaint may not be about working in both places but, rather, having changed to full time status at Emory.

Mr. Goldstien notes that some groups have “seized” on these allegations to discredit the studies Dr. Thorsen worked on:

Anti-vaccine groups have seized on the allegations to contend that scientific studies disproving the vaccine link to autism are wrong. Those groups have long argued that thimerosal, a preservative in some vaccines, can cause autism, as can the MMR vaccine for measles, mumps, and rubella.

“I think it is quite significant,” said Dan Olmsted of the Age of Autism. “I think someone allegedly capable of ripping off his own university by forging documents from the CDC is capable of pulling off anything.”

And this is where the this situation becomes very important. If these allegations are true, does this negate the studies Dr. Thorsen worked on?

Mr. Goldstein addresses this with quotes from Mr. Olmsted (above) and people at the CDC and Denmark.

“Poul Thorsen had absolutely no influence on the conclusions regarding this paper,” wrote Mads Melbye, head of the division of epidemiology at the Statens Serum Institut in Copenhagen and senior author of the study, in response to e-mailed questions.

“Thorsen was not actively involved in the analysis and interpretation of the results of this paper,” Melbye said.

The second study, published in Pediatrics in 2003, examined 956 Danish children diagnosed with autism from 1971 to 2000. It concluded the incidence of autism increased in Denmark after thimerosal was removed from vaccines.

Kreesten Meldgaard Madsen, the lead author, said Thorsen played a minor role.

“Dr. Thorsen was not in a position to change or compromise the data,” Madsen wrote. “Dr. Thorsen was part of the review cycle, but never very active in giving input. Dr. Thorsen never had access to the raw data nor the analysis of the data.”

I doubt these statements will mollify Mr. Olmsted’s readers.

In a piece on WHYY (a public radio station in Philadelphia) has a story, Investigation of autism researcher’s conduct sparks controversy.

Dr. David Mandell of the Center for Autism Research agrees the studies Thorsen worked on should be reviewed. But he doesn’t believe the research has been compromised. He noted that Thorsen was not a lead researcher, the studies used government data, and they were peer-reviewed. This view is echoed in a statement from the Centers for Disease Control, which partly funded the vaccine research.

So, where does this leave us? With a lot more questions than answers still. One question in my mind at least is whether Dr. Thorsen is accused of transferring money to his own use or if he is accused of transferring money to fund his research at Emory when he left Aarhus. That aside, no matter what happens from here, this will be used to imply that vaccine-autism research (and not just that by Dr. Thorsen) is performed by corrupt individuals and should not be trusted.

Assume that the allegations are real. I can state that I am very angry at that possibility. I do not like dishonest people. I do not like dishonest researchers.

Mostly, I don’t like the fact that this will be (and already is being) used to put doubt in a lot of people’s minds about the role of thimerosal and MMR and autism. $2M is a small sum compared to the amount of suffering that will go on as this breaths a little life back into that movement.

My guess is that some readers are now ready to blame me of bias, of believing that Dr. Thorsen’s studies are accurate when I should be questioning everything he did. Let’s ignore the statements by his collaborators that Dr. Thorsen didn’t have access to the data to manipulate. Let’s just stick with the fact that the studies Dr. Thorsen worked on agree with the results of multiple other studies. The surprising outcome would be if on review the conclusions changed.

I am sure this story isn’t going away. And it should not. We need to know and we deserve to know what the details are here. Beyond that, I am sure that this will be forever in the lore of the vaccines-cause-autism community and will be used to convince ever more people to join.

For that, whoever is responsible for this mess, I am angry.

California’s Invisible Autism Epidemic Continues

13 Feb

Over a year ago, I wrote a post at Autism Street titled,
“California’s Invisible Autism Epidemic“.

At the time, IDEA child count and population data was available through 2007. Admittedly, what follows is a bit of a repeat, but there is updated information included too.

That January 2009 post asked the following question:

It would seem that many an “autism advocate” has warned us of an impending “crisis” that looms for California’s healthcare systems and schools. If autism caseload is increasing, and it represents a real increase in autism itself, then a next logical conclusion is that, ceteris paribus, similar increases will also be seen in the total numbers of children in special education in California’s schools, right?

And suggested an answer:

Wrong – well, maybe wrong.

Another year has passed, and IDEA data for 2008 is beginning to become available. Here’s what the preliminary IDEA data for California kids in elementary, middle, and high schools shows for autism now:

Autism

To borrow a phrase from Bev over at Asperger Square 8, “Don’t Panic!”.

Also, please remember, that like the CDDS client data, the IDEA is not descriptive epidemiology.

The USDE data are not reliable for tracking the prevalence of autism, and they in fact never were meant to fill this need.

Source

What we can actually learn from this, is that the increase in the number of kids receiving special education services who wear an “autism” category label continues to increase.

Of course the, “not so fast” is next.

The Invisible Epidemic

The next graph shows a bigger picture in California. It’s the number of students (age 6-17) receiving special education services, as a percentage of the population (age 6-17) for all disability categories.

All Disabilities

The percentage has been flat, at a little under 9.2%, for 11 straight years. How is this possible? If there have been “epidemic” increases in the autism category, all things being equal, we should have seen this number rise, shouldn’t we? And therein lies one potential answer – all things are probably not equal. It’s true that within the IDEA data for California, the increase in the use of the “Autism” category label is not offset by decreases in the use of the category label “Mental Retardation”. The increase is also not offset by a corresponding decrease in use of the label “Speech or Language Impairment”.

Speech or Language Impairment

A communication disorder such as stuttering, impaired articulation, a language impairment, or a voice impairment that adversely affects a child’s educational performance.

Source

So what else is there? Something big in California?

Autism and SLD's

Specific Learning Disability

A disorder in one or more of the basic psychological processes involved in understanding or in using language, spoken or written, that may manifest itself in an imperfect ability to listen, think, speak, read, write, spell, or to do mathematical calculations, including conditions such as perceptual disabilities, brain injury, minimal brain dysfunction, dyslexia, and developmental aphasia. The term does not include learning problems that are primarily the result of visual, hearing, or motor disabilities, of mental retardation, of emotional disturbance, or of environmental, cultural, or economic disadvantage.

Source

I can still see how, in days of lower awareness and recognition of autism among parents and educators, an autistic child could easily be placed in this category (as a kind of catch-all), based on the first portion alone – “A disorder in one or more of the basic psychological processes involved in understanding or in using language, spoken or written…”. It could even be the case, that alongside less awareness and recognition, there was also some degree of unwillingness to use a category label like “Autism” on the part of both parents and educators.

Interestingly, the apparent in increase of .09% of the resident population categorized under “autism” appears to be offset by a .09% of the resident population decrease for “specific learning disabilities” in 2008.

Source data can be found at http://www.ideadata.org

Maternal age affects autism development?

10 Feb

A new study that looked at a large birth cohort (almost 5 million participants) over a 10 year period has announced that maternal age is an indicator of developing autism with an approximately 50% higher risk for a woman in her forties than a woman in her twenties.

The researchers looked at the records for all births in California between Jan 1990 and Dec 1999. Cases of autism were identified from this cohort using the records from the Early Start Report (ESR) for children under three, and the Client Development and Evaluation Report (CDER) for children over three.

A diagnosis of autism was defined as either positive for Developmental Disabilities on the ESR, or an autism level of one a CDER record/ICD code for autistic disorder. After excluding children from multiple births and those with missing data there were 12,159 cases and 4,935,776 controls.

Thats an interesting autism rate of 0.2% which might indicate more than maternal age that ESR or CDER is not that good at catching autism diagnoses as its a very low rate compared to the US national 1%.

This paper also lacks strength when looking at confounding factors – admittedly a tricky proposition as we don’t know what causes autism – but it may be of interest that the confounding factors that they _did_ account for were mainly ethnocentric i.e. race, gender etc and that they found that yep – whites were mainly very well represented. It seems very likely therefore that of possibly more interest that maternal age might be that not enough efforts are being made by local authorities to go into non-white enclaves.

More on autism “clusters”

4 Feb

There are regions of California where the autism “rate” is much higher than in other regions. If you are a regular reader of this blog, you are likely thinking “repeat!” Yes, between Kev and myself and even the Evil Possum himself, David N. Brown, we have about 10 posts about the GMC ruling on Andrew Wakefield and the retraction of his article in The Lancet. Now another “autism cluster” post?

Only a month ago I blogged “Autism Clusters Found: areas with high incidence of autistic children“, discussing a paper by Dr. Hertz-Picciotto at the U.C. Davis MIND Institute. Well, it turns out that another “cluster” paper has been published. This article, The spatial structure of autism in California 1993-2001, is by Prof. Bearman’s group at Columbia. This is the same group that recently published Diagnostic change and the increased prevalence of autism

Here’s the abstract:

The spatial structure of autism in California, 1993-2001.

Mazumdar S, King M, Liu KY, Zerubavel N, Bearman P.

Institute for Social and Economic Research and Policy Columbia University, New York, NY, USA.

This article identifies significant high-risk clusters of autism based on residence at birth in California for children born from 1993 to 2001. These clusters are geographically stable. Children born in a primary cluster are at four times greater risk for autism than children living in other parts of the state. This is comparable to the difference between males and females and twice the risk estimated for maternal age over 40. In every year roughly 3% of the new caseload of autism in California arises from the primary cluster we identify-a small zone 20km by 50km. We identify a set of secondary clusters that support the existence of the primary clusters. The identification of robust spatial clusters indicates that autism does not arise from a global treatment and indicates that important drivers of increased autism prevalence are located at the local level

They used data from the California Department of Developmental Services (CDDS). This dataset has been discussed a lot online. While the work of Dr. Bearman’s group and Dr. Hertz-Picciotto’s group are both much more rigorous than the simple comparisons done by myself and others, there are severe limitations in using CDDS data. The CDDS does not make an effort to seek out all autistics, for one thing. There are variations by Regional Center in identification and services for disabled Californians.

That said, Prof. Bearman’s group found a large “cluster”. If a child was born in this region, he/she is about 4 times more likely to be listed by the CDDS with the label of autism than if he/she were born in the rest of California.

The cluster is in the Los Angeles area. (map was taken from the Wall Street Journal’s story, L.A. Confidential: Seeking Reasons for Autism’s Rise)

Prof. Bearman’s group checked that the cluster was stable over time and found that there was a region with the high administrative prevalence existed for 5 or more years. That is one good check that this is a “real” cluster and not a statistical artifact.

The Wall Street Journal quotes Prof. Bearman:

Dr. Bearman says he believes social influences are the leading cause for the high autism rates in Los Angeles, although the researchers continue to examine environmental issues.

Other studies have shown that older parents run a greater risk of having an autistic child. But when the Columbia researchers adjusted the Los Angeles cluster to factor out parental age, the higher levels remained. Dr. Bearman says he believes the high levels will also remain after the data are adjusted for education levels, socio-economic status and other demographic characteristics in future studies.

You may recall that the MIND Institute study found multiple “clusters”, using different criteria.

There is a cluster roughly centered on Hollywood in those maps, consistent with the newer Columbia study. (as an aside, the closeup map from the MIND Institute press release doesn’t look like the same region to me.)

It seems reasonable to assume that both groups were looking for clusters in a search for a possible “hot spot” of some environmental trigger for autism. Instead, Bearman’s group indicates “social issues” and Hertz-Picciotto’s group found parental education and proximity to autism treatment centers were linked to the “clusters”.

Both groups are to be commended, in my view. They are looking for some answers on causation. They are working with data that are much less than high quality, and they are dealing with shifting awareness and societal influences which could cloud any trends that may or may not exist.

Autism Epidemic Talk

20 Jan

A couple of slap dash blog pieces appeared today both on the same subject – the so called autism epidemic. First off is Harold who writes about a series of interviews with David Kirby. David says:

<blockquote>It’s crazy that in this debate, we’re still debating whether autism numbers are actually going up or not, which is insanity to me. It’s people desperately clinging to this belief that autism is genetic, that it’s always been with us at this rate, that we’re just better at counting it, better at diagnosing it.</blockquote>

Harold claims David has ‘hit the nail on the head’ with this quote. I disagree with Harold and I disagree with David. Its far from insanity to examine a perfectly valid hypothesis. More later.

Anne Dachel at the Age of Autism writes :

<blockquote>Why do I personally know so many young people with severe autism, whose symptoms can’t be ignored?  How could we have just ignored these people in the past?  Where are those misdiagnosed adults with classic autism—those with the same symptoms we see in so many children today?

I’m not talking about [Kristina] Chew’s autistic neighbor who was able to have a conversation with her, or [Paul] Offit’s people who are kind of ‘quirky.’  I mean adults who can’t talk, those in diapers, people who scream for hours and pound hours in walls and who constantly rock back and forth.</blockquote>

Dachel goes on to list several news reports which question the idea of there not being some kind of an epidemic. I disagree with her view and I disagree with the way she has reached her view.

Both Dachel and Harold (and David Kirby come to that) are claiming that epidemiology can be ursurped by individual experience – Dachel’s individual experience with ‘so many young people’ and David’s individual experience with the idea that people are desperately clinging on to some sort of belief in a genetic form of autism.

Now, casting aside the fact that the some of the forms of autism that we know about (Rett Syndrome etc) _are_ solely genetic we have to – as we do with _all_ forms of science, cast aside personal anecdote when making sweeping statements about a very large group of people. What we need to do instead is look at the science. So what does the science say?

Nothing. As far as I can see no firm case has been made that there either is or is not an autism epidemic. Why? Because the science hasn’t been done. It is maybe worth noting that it is the firm opinion of autism experts that a large part of any possible rise is due to:

a) Better diagnostic tools

b) More places at which to recieve a diagnosis

c) More awareness amongst clinicians of autism

d) Earlier diagnosis

e) Diagnostic substitution

f) Widening of diagnostic criteria

Experts such as Eric Fombonne, Roy Richard Grinker and Simon Baron-Cohen have all spoken about these ideas at length. However, that doesn’t make them right. There still seems to be no hard and fast science that says there is an autism epidemic or not.

Autism Clusters Found: areas with high incidence of autistic children

1 Jan

Researchers at the U.C. Davis MIND Institute has discovered regions in the state of California that have notably higher autism incidence. But the story is more complicated, and more sad, than one might think at first. Instead of indications of an “autism epidemic”, these clusters point to the fact that minority and poor children are much less likely to receive autism diagnoses.

I don’t have the paper yet (I’m still trying to find the abstract), but articles in the Woodland Daily Democrat and the San Diego Union-Tribune are reporting the story.

The clusters do not appear to point to environmental causes. Instead…well, read for yourself:

Researchers said that in this investigation the clusters probably are not correlated with specific environmental pollutants or other “exposures.” Rather, they correlate to areas where residents are more educated.

Children with autism diagnoses in these clusters are more likely to be White and have parents with high education levels. Again, a quote:

“In the U.S., the children of older, white and highly educated parents are more likely to receive a diagnosis of autism or autism spectrum disorder. For this reason, the clusters we found are probably not a result of a common environmental exposure. Instead, the differences in education, age and ethnicity of parents comparing births in the cluster versus those outside the cluster were striking enough to explain the clusters of autism cases,” said senior author Irva Hertz-Picciotto.

Kids in the “clusters” are about twice a likely to be diagnosed autistic and kids in nearby areas.

Twice as high.

To the many of us armchair epidemiologists who who have looked closely at the California Department of Developmental Services (CDDS) data, this comes as no surprise.

For me, the most memorable discussion of the autism clusters came from Autism Diva, in her post from July 1997, Malibu and Compton: Compare and Contrast.

Here is a graph from that post:

The South Central Regional Center, in a predominantly non-White, poor area of the Los Angeles basin, had an administrative prevalence of 33 per 10,000. Compare that to Westside Regional Center with a prevelance of 84. Westside is a much more affluent are with a higher proportion of White families.

From the San Diego Union-Tribune:

“There is mounting evidence that at least some of this clustering results from the greater access and utilization of services by those with more years of schooling,” the UC Davis researchers wrote.

Yes, there is a certain “I told you so” moment here. This blog, Autism Diva, Autism Natural Variation, Autism Street and others have been pointing out the apparent autism clusters in the raw CDDS data for years. Long before I started blogging. But the real story isn’t the effect such clusters have on the idea of the “autism epidemic”. Rather, this is a clear indication that we are underserving the disabled in our minority and poor communities. This is just plain wrong.

It is long past time for real autism advocacy organizations to work on increasing awareness and access to services in underserved areas. The autism “clusters” are probably not real. From where I sit, what is real are the “anti–clusters” of undiagnosed autistics, minorities, the poor, and, yes, adults.

CDC report 1 in 110 kids are identified autistic

19 Dec

You’ve probably already heard–the CDC’s estimate of the autism rate was announced as 1% today. This was published in an MMWR came out today, with the new CDC prevalence estimate of 1 in 110. I made some notes on the conference call, but I thought it worthwhile to make a few comments on the document itself.

This is the third in the autism prevalence MMWR’s. The first was
Prevalence of Autism Spectrum Disorders — Autism and Developmental Disabilities Monitoring Network, Six Sites, United States, 2000

and

Prevalence of Autism Spectrum Disorders — Autism and Developmental Disabilities Monitoring Network, 14 Sites, United States, 2002

This new one is titled

Prevalence of Autism Spectrum Disorders — Autism and Developmental Disabilities Monitoring Network, United States, 2006

In each they estimate the prevalence for 8 year olds. So, the 2000 study was on children born in 1992 and the 2002 study was on children born in 1994. They found prevalences of 1 in 166 (200) and 1 in 150 (2002), respectively.

The new prevalence is 1 in 110 for 2006 (8 year old children born in 1998). This is a big jump, no doubt. It is worth taking very seriously. Unfortunately, it isn’t as simple as saying, “the number of autistic children has increased”.

As the authors note in the introduction:

Since the early 1990s, the number of persons receiving services for ASDs has increased substantially. However, identifying children for services for autism might not be equivalent to using consistent diagnostic standards to identify persons in the population because services within communities are not available uniformly to all persons with ASDs. For this reason, studies that rely exclusively on single-source administrative datasets (e.g., disability service records or annual reports of special education counts) most likely underestimate ASD prevalence and might not adequately capture changes in the ASD population over time

Most of the states reporting in the ADDM use more than a single source. Most use medical and educational records. Those that use a single source (e.g. Florida) show lower prevalence estimates.

Let’s get back to that 1% estimate. This is a big jump in the prevalence–with the previous prevalence being 1 in 150 (about 0.67%). Yes, it should be taken seriously, but at the same time 1% is not a surprising number. The authors list 5 studies that show a prevalence >1%, using other methods.

Note that this is for the 1998 birth cohort, children born 4 years after those studied in the previous MMWR. I bring this up because the “buzz” before the MMWR was discussing this as the 1996 cohort. The studies are not spaced out evenly in time–2000, 2002, 2006.

Methodology
The methodology is through a record screen, not through direct observation of children:

Children aged 8 years with a notation of an ASD or descriptions consistent with an ASD were identified through screening and abstraction of existing health and education records containing professional assessments of the child’s developmental progress at health-care or education facilities.

If on review of the records, the child is deemed to meet the DSM-IV criteria for autism, he/she is counted. This is a good way to get an estimate, but there is a lot of room for children to fall through the cracks, in my opinion. As such, it is and has always been, an underestimate. In some cases, it is probably a very large underestimate. As will be shown below, there is a big variation by state–a factor of 3. I don’t think anyone really believes that the autism prevalence in Florida, or the prevalence amongst Hispanics is much lower than in other states or other ethnicities.

It is interesting to note that the ADDM network does find a significant number of children whom they (the ADDM) categorize as autistic even though they haven’t been given that diagnosis before. About 23% of the autisistics counted in the 1% value were not identified before the ADDM did their review.

That’s worth repeating–about 23% of 8 year olds identified as autistic were mislabeled as non-autistic by their schools, parents and doctors. That’s an interesting fact for those who claim that autism is easily identified.

The CDC study is not capable of explaining whether part of the increase represents a “real” increase in the number of autistic kids. It certainly can’t go into whether or not any specific proposed cause is valid. However, one can use the data to test hypotheses. This type of study just isn’t capable of making claims about causation.

States Reporting to the ADDM

This new study covers children born in 1994 living in 11 states:
Alabama, Arizona, Colorado, Florida, Georgia, Maryland, Missouri, North Carolina, Pennsylvania, South Carolina, and Wisconsin.

Note that this is different from the last MMWR, which looked at kids born 2 years earlier (1996) and included sites in:
Alabama, Arizona, Arkansas, Colorado, Georgia, Maryland, Missouri, New Jersey, North Carolina, Pennsylvania, South Carolina, Utah, West Virginia , and Wisconsin.

The new study added Florida, but took out Arkansas, New Jersey, Utah and West Virginia. These changes do make it more difficult to compare the prevalence data. They do not explain the increase. By that I mean, it isn’t as though the low prevalence states were removed from the previous MMWR study and high prevalence states were added.

I would have been very interested what happened to the prevalence in New Jersey. The last two MMWRs had New Jersey at about 1%. A good comparison would be if that state had the same autism prevalence or a higher value.

Prevalence by state

Data in Table 2 from the MMWR. Data from 11 states were reported. The prevalence ranged from 4.2 (Florida) to 12.1 per 1,000 (Missouri and Arizona). That’s a big spread, a factor of 3. The highest prevalence was for males in Missouri–19.1 per 1,000 (1.9%, or 1 in 52).

There was some variation in the male:female ratio, from 3.2 (Alabama) to 7.6 (Florida). Again, this shows that there is a big variation by state in how autistics are identified.

Variation by ethnicity.

There is a large difference in the prevalence by ethnicity. This also varies by state. For example, there is a 9.4 White-to-Hispanic ratio in Alabama, but the same ratio is only 0.7 in Florida. In general, Whites are identified more often than either Hispanic or African Americans.

We have a lot of work to do in making sure minorities are correctly identified and getting appropriate services and supports.

Earlier age of identification.

The median age of autism diagnosis is about 4.5 years. This is a big jump down from the 2002 data, which had a median of 5 years. That is a good thing.

This is worth a couple of comments. First, there is still room for improvement. Most of the children had development concerns noted in their records before age 2. The obvious question is whether these children could have been identified sooner. This was one comment stressed by the CDC in the conference call.

It is also worth noting that autism isn’t “obvious” or “easy” to identify autistics. 4.5 years old is the median age.

It is also worth noting that the big jump down in median age of identification is a very clear indicator that, yes, people are getting better at identifying and diagnosing autistics.

The range of age of identification is as low as 2 months (!) to as high as 106 months. The low end is pretty remarkable. I don’t think there are any tests qualified for such young children. At the high end, that is nearly 9 years old. Again, this goes to the idea that autism is not obvious.

One complaint that is always used in these discussions is “what, are you saying that no one noticed these kids?”. No. They likely had other diagnoses or that some concerns were noted about development for them.

Number of kids receiving special education services.

Table 3 of the report is quite interesting. They show for six states what fraction of identified autistic kids are getting special education, and under what primary label.

In Colorado, 76% of autistic students are in special education, while in Arizona it is 96%. Is there really such a big difference in the needs of these kids from state to state?

Colorado has only 34% of the autistic students under the primary category of autism. Compare that to Maryland with 76%. Again, it is pretty clear that there is a lot of variation in how special education services are granted by state.

Cognitive Functioning

From the MMWR:

Data on cognitive functioning are reported for sites having IQ test scores available on at least 70% of children who met the ASD case definition. The proportion of children with ASDs who had test scores indicating cognitive impairment (IQ ?70) ranged from 29.3% in Colorado to 51.2% in South Carolina (average: 41%)

I find this information rather interesting. Most of the children with IQ data were not cognitively impaired.

2004 Prevalence data.

There was also a small appendix released today, with information on 2004 prevalence data (note that the study noted above is for 2006). Those data show a prevalence of 8 in 1,000, or 1 in 125. This is a “smaller scale effort”

It is interesting to put the data from the various studies into a timeline:

2000 originally 1 in 166, revised to 1 in 150 (6.7 per 1,000) (1992 cohort)
2002 1 in 152 (6.6 per 1,000) (1994 cohort)
2004 1 in 125 (8.0 per 1,000) (1996 cohort)
2006 1 in 110 (9.0 per 1,000) (1998 cohort)

If you recall, David Kirby claimed the new CDC data would support his hypothesis that the Hepatitis B vaccine caused an upsurge. Mr. Kirby mistakenly assumed that the 1% figure would be for the 1996 birth cohort. Mr Kirby then correlated the jump from 1 in 150 to 1 in 100 with the uptake of HepB vaccination in that birth cohort. He stated (incorrectly, we now know):

But according to the CDC’s National Immunization Survey (which also includes parental telephone interviews), only 8% of infant children received the Hep B vaccine in 1992, when that birth cohort showed an ASD rate of 67-per-10,000.

By 1994, the number of children receiving Hep B vaccine had reached just 27% — and the cohort showed a similar ASD rate.

But the Hep B coverage rate had risen to 82% by 1996, when that cohort’s ASD rate rose to around 100-per-10,000.

So, there was a smaller jump that correlates with the uptake in HepB in the 1994 cohort–the rate increased from 0.66% (1994) to 0.80% (1996). Then, two years later, there is a similar jump, from 0.80% (1996) to 0.90%. But, this time without the big increase in HepB vaccination.

Not so dramatic a story with the real data. Just a constant rise.

Final words

I hope this highlights some of the information in the study. I wish I had the time to spend to make this summary a bit easier of a read. But, there are other posts to write. Like one talking about Autism Speaks and the way they are capitalizing on the new prevalence numbers with a very deceptive graph.

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