1/07/2010

Clusters of Autism in CA: Better Educated Parents Are the Common Denominator

In this month's Autism Research journal, Van Meter, Christiansen, Delwiche, Azari, Carpenter, and Hertz-Picciotto looked at whether it was possible that prenatal environmental exposures were responsible for an increased autism incidence. What they found was that the autism clusters they identified were not associated with any environmental exposures but were related to parental education levels (and note that we're talking about a researcher on a study from last year that drew some heat for having a press release that was substantially different from the actual study's conclusions-- see here for an interview with Hertz-Picciotto that addresses the discrepancy).

MedPage Today has an audio interview with Hertz- Picciotto and an accompanying article explaining why people living in these cluster areas should not be worried that it means they are at increased risk for autism in their children, as well as to why this would appear to be an artifact of better reporting rather than a true disparity in the number of autism cases across the population.

While all this is well and truly interesting, I found other things in the study to be of specific interest, especially based on the way that the folks at AoA and the like attached themselves to last year's study by Hertz-Picciotto and Delwiche, which concluded:
"In summary, the incidence of autism rose 7- to 8-fold in California from the early 1990s through the present. Quantitative analysis of the changes in diagnostic criteria, the inclusion of milder cases, and an earlier age at diagnosis during this period suggests that these factors probably contribute 2.2-, 1.56-, and 1.24-fold increases in autism, respectively, and hence cannot fully explain the magnitude of the rise in autism. Differential migration also likely played a minor role, if any. Wider awareness, greater motivation of  parents to seek services as a result of expanding treatment options, and increased funding may each have contributed, but documentation or quantification of these effects is lacking. With no evidence of a leveling off, the possibility of a true increase in incidence deserves serious consideration."
A careful reading of the actual study notes that the inflammatory rhetoric of those who used the press release as a testament to the epidemic of autism is not warranted. Joseph at Natural Variation examines the discrepancies in the press release, noting that it is off the mark of what the actual study found. Hertz-Picciotto addresses it, as well, with Lisa Jo Rudy:
"The relationship to the investigation of environmental causes is not the subject of the paper, and the press release did go somewhat astray. Here is the connection, in the big picture: as we pare away, one by one, the artifacts (changes in definition, inclusion of milder cases, and earlier age at diagnosis, each of which contributes to or reflects 'better ascertainment' or 'greater awareness'), we are not yet able to explain all of the rise. I don't know how much of it is due to a true increase in cases, and in fact, nobody does."
I'm sure that it's no surprise to anyone that AoA might misread something. Look what they're doing with the new consensus reports from Pediatrics. And notice that once again, another day passes with no mention of the Zakh Price story, not even to ask loyal supporters to donate to Carole Reynolds so that she can get her grandson the legal support he needs to face this court hearing. But I digress.


In this study, "The Rise in Autism and the Role of Age at Diagnosis" from 2009, we have language discussing the dramatic increase in autism since the 1990s, noting that for the 2000-2001 birth cohorts, that the prevalence of autism in California was .4%  or 1 in 250 (40 in 10,0000 and not including all ASDs). And yet, in this month's study, cowritten in part by these two same researchers, we have language which downplays the idea of autism as an epidemic while still noting the 40 in 10,000 prevalence of autism. Yet here, in this study (Van Meter et al., 2010), the magnitude of the numbers is not attended to.  Indeed, the authors in the present study note that autism "is sufficiently rare that, e.g. two siblings with autism could constitute a highly significant spatial cluster in a certain CDT" (p.2). Where did the intensity of Hertz-Picciotto and Delwiche(2009')s "major public health and educational concern" go? And isn't it interesting that AoA mentions this latest study not at all. Hmmm.

References:

Hertz-Picciotto, & Delwiche, L. "The Rise in Autism and the Role of Age at Diagnosis." Epidemiology:
2009, 20:1; 84-90.
 
Van Meter KC, et al "Geographic distribution of autism in California: A retrospective birth cohort analysis" Autism Res 2010; 3: 1–11. (links to abstract, can provide actual study via email)

1 comment:

Joseph said...

I'm glad to see that Dr. H-P corrected the press release. It was quite appalling.

Note, however, that she mentions awareness as one of the artifacts. H-P et al. (2009) did not quantify the impact of awareness at all. I do think there are ways to do that.