Friday, July 09, 2010

Comment Spam at Blogger Getting Out of Hand

I've changed my comment policy slightly. I'm enabling comment moderation in posts that are older than 365 days.

This morning I got spammed in a way I've never been spammed before. A spam-bot with the handle xiaoyu posted the same comment spam in what appears to be each and every one of my blog posts.

It's a shame that Blogger doesn't have a good way to deal with comment spam. Their captcha obviously isn't working very well. Unfortunately, I don't believe spam-filtering is a breeze in other platforms either.

Wednesday, May 19, 2010

80% Divorce Stat is Complete Garbage

Of course, we already knew that. There's a prior survey by Easter Seals on the question of divorce among the parents of autistic people.

Readers might remember I also tackled another 80% stat having to do with the divorce rate of autistic adults.

Both 80% stats are clearly made up. They are impossible to track back to original sources. The question is: Who made them up, and for what purpose?

Either way, do check out the story:

80 Percent Autism Divorce Rate Debunked in First-of-Its Kind Scientific Study.

Monday, April 19, 2010

The Anti-Vax Movement Still Peaked in 2002-2003 and MJ's Excuses are Trivial to Address

MJ has written yet another rebuttal of my post on the media's interest in the anti-vax movement.

MJ's primary argument is basically that the absolute article count for "autism vaccines" has grown. The count for "autism" has simply grown more. I say that the relative count is what matters, but let's look into this in more detail.

As I've noted in comments, MJ fails to take into account that the total number of articles indexed by Google News Archive has also grown from year to year. Presumably, this doesn't mean people are reading more newspapers, but simply that Google is adding sources to its index all the time.

Estimating the total number of articles in Google News Archive could presumably be problematic algorithmically for Google. I have some ideas which I mentioned in comments, but I'm not confident that they would be unbiased.

Instead, let's check if searches for "autism genetic" relative to "autism" have the issue MJ thinks relative counts have.

They do not. There's no peak in 2002 here. There's no downward trend after 2002. There's no dilution of the word "genetic" in autism articles as more topics are covered. What we see instead is a remarkably stable trend.

We previously also looked at relative counts for "neurodiversity", which MJ had verified as well. This analysis also fails to support MJ's hypothesis. The same is the case of several other trends I've checked which I'm not going to go into here.

It's also illustrative to look at the raw article counts for "vaccine injury" (in quotes). These counts are presumably also biased by increasing coverage of autism topics, but maybe less so.

What we see here is consistent with a peak in 2002-2005, and a brief recovery in 2008 due to substantial propaganda efforts in relation to Jenny McCarthy and Hannah Poling. This effect cannot be expected to last very long, though.

MJ has failed to explain why the pattern of media coverage for "autism vaccines" generally matches VAERS autism submission trends and the number of autism cases filed with the vaccine court. It's lazy and convenient to simply say "the data was not meant to track this." What is the explanation?

Additionally, Smith et al. (2007) reports that:
MMR vaccine remains the number one ‘top of mind’ vaccination issue for parents. The proportion of parents believing MMR to be a greater risk than the diseases it protects against has fallen from 24% in 2002 to 14% in 2006. The proportion of ‘hard-core rejectors’ of MMR vaccine remains stable at 6%. There has been a gradual and sustained increase in the proportion of parents across all social groups saying MMR was completely safe/slight risk rising from 60% in 2002 to a current level of 74%. There now appears to be a sustained move away from fears over MMR safety and belief in the unfounded link to autism towards a more positive perception of the vaccine.

(My emphasis.)

Finally, an immunization report by the British NHS shows that MMR coverage had a low in the 2003-2004 period.


I've perseverated on this a lot more than I probably should, and I've gone out of my way to address ridiculous criticisms put forth by MJ.

Saturday, April 17, 2010

MJ Reproduces A Result of Mine

The anti-vax movement peaked in 2002, maybe in 2003. There are several different lines of evidence that point in this direction. I recently presented just two of them: Google News Archive articles matching "autism vaccines" relative to "autism" articles, and VAERS report submissions. Additionally, Sullivan over at LB/RB has put forth a graph of cases before the US vaccine court.

It's not surprising that such easy-to-confirm observations would hit a nerve with some people. Commenter MJ took issue with my methodology, at first claiming that as more autism articles are written, the word "vaccines" would tend to become rare in them, and later claiming that Google News Archive does not have the right bias for this type of analysis. None of this made any sense to me, and you can read the exchange in comments.

Then MJ wrote a post in response to my analysis where, evidently, MJ has come up with a reproduction (not repetition) of my prior result. You can see MJ's graph (which I copied with "fair use" in mind) on the right.

MJ takes comfort in the fact that newspaper articles matching the word "neurodiversity" are quite uncommon, relatively speaking. But see – and I doubt MJ doesn't realize this – that's a comparison of apples to oranges. Articles matching "autism vaccines" are about a public health issue, one that is bound to interest all kinds of readers. They are articles about court cases, studies, etc. Articles on neurodiversity are about an ideology, which reporters might not cover simply because they don't see a payoff in covering it.

If you're going to compare them, it obviously only makes sense to compare trends, not absolute article counts. MJ's scaling obviously doesn't allow us to see a trend, so I've produced the following graph.

It's an entirely different pattern. (Note that since article counts are relatively small, there's bound to be more noise in these series.)

One More Thing

Regarding VAERS, MJ says:
As for VAERS, it wasn't meant to do this sort of tracking nor is it an accurate measure of all children who had a reaction to a vaccine - especially for controversial relationships like autism.

I didn't look at a measure of "reactions" – and it's not clear if reports with "autism" as a symptom are even valid. I looked at submission counts. These are clearly a valid proxy of new parents recruited into either an anti-vax mindset or vaccine litigation.

Friday, April 16, 2010

IDEA's Bass Diffusion Model

In the previous post I argued that a Bass Diffusion Model fits the administrative prevalence of autism in California remarkably well, and made specific predictions based on this observation. You can think of a Bass Diffusion Model as a word-of-mouth or an adoption-of-innovation type of model.

For the sake of completeness, I will now present a couple of Bass models I derived for the administrative prevalence of autism at the US level, based on data from the Department of Education, otherwise known as IDEA data. The following is a graph of the 6-17 IDEA prevalence along with Bass model hind-casting and forecasting all the way to 2030.

Model # 2 (the red line) is the one I prefer in this case. (I'll explain why shortly.) It predicts that prevalence will eventually level off at almost 1.1%. This is completely plausible, not only because that's roughly the new consensus prevalence of ASD, but also because Minnesota is already there.

I also find it to be a fascinating prediction of the model. If you recall, a Bass model predicts a maximum prevalence of about 0.65% (at most 0.7%) for children 6 to 9 in California DDS. This absolutely makes sense. California DDS is not like IDEA. DDS does not find every autistic person to be eligible for services, and not all developmentally disabled Californians pursue eligibility with DDS. So, in my view, a Bass model makes predictions that are remarkably consistent with our current reality.

If the models are correct, by 2013 IDEA prevalence should just have surpassed 80 in 10,000. Additionally, a leveling-off trend should not be completely evident yet. It may be slightly noticeable. Meanwhile, in the California report of Q4 2013 (and let's hope they produce data equivalent to that of reports currently available) a leveling-off trend should already be evident in the 6-9 cohort.

Technical Details

For formulas and variable names, see the California post. Parameters of both models are, again, estimated by means of genetic programming. For model # 1 I simply tried to fit the 1993-2007 prevalence series without any modifications. The resulting parameters were:

p = 4.808·10-8
q = 0.22
t0 = 1938.809 (year)
m = 118.32 (per 10,000 population)

Model # 2 is based on the observation that IDEA practically did not have an autism category prior to 1993. However, once the category was introduced, many children would've been put in the category all at once. It's like introducing a product into the market that already has a number of owners. So I performed the calculation by reducing the prevalence in all report years by 3.864, which is the 1993 prevalence. Hence, t0 should be equal to 1993. The parameters actually derived by the code I wrote were:

p = 0.0072
q = 0.222
t0 = 1993.03 (year)
m = 105.992 (per 10,000 population)

Note: In this case, model results must be added to 3.864 to obtain the projected prevalence.

The rationale of the derivation of Model # 2 makes sense to me, and that's why I prefer it. However, there's not a huge difference between the models.

Addendum (4/16/2010)

I forgot to mention that the correlation coefficient R for both models was approximately the same: 0.99993. This is exceedingly good, and better than the fit for CalDDS.