Increasing parental age and autism severity?

An interesting paper by David Geier and colleagues [1] (open-access here) caught my eye recently, concluding that there was a lack of support for the suggestion that: "increasing parental age was associated with increasing autism spectrum disorder phenotypic severity".

"the snozzberries taste like snozzberries".

Before progressing through the paper and its possible implications, the eagle-eyed out there might have already spotted the name Dr Brian Hooker on the authorship list of the Geier paper. Outside of his other peer-reviewed work [2], I probably only need to mention the letters 'CDC' and everything that has [so far] followed including (at the time of writing) a removal statement retraction statement (updated: 04/10/14) for another paper [3]...

Anyhow, the idea behind the Geier paper stems from the quite widely disseminated notion that there may be a connection between increasing parental age at conceiving and an increased risk of offspring autism. I've covered it a few times on this blog (see here and see here). The authors elaborate about a recent hypothesis suggesting that "there must be a linkage between increasing genetic load and increasing parental age in autism spectrum disorder pathogenesis" based on studies like the one from Kong and colleagues [4] (covered in a previous post) and Lampi and colleagues [5]. Further, that as a consequence of an increasing genetic load (all those SNPs et al), "there should be a significant relationship between increasing parental age and increasing autism spectrum disorder phenotypic severity of subjects diagnosed with an autism spectrum disorder".

The paper is open-access but maybe a few details are in order:

• Participants (N=351), diagnosed with DSM-IV autism, were drawn from "patients presenting for outpatient genetic consultations at the ASD Centers, LLC". Mean age was approximately 9 years of age, most male and most reporting developmental regression following birth. Details of age of parents at time of offspring birth were analysed alongside use of the ATEC (Autism Treatment Evaluation Checklist) at initial clinical presentation. These variables formed the crux of the study.
• Results: "Overall, it was observed that no significant relationships were observed between increasing autism spectrum disorder phenotypic severity and increasing maternal or paternal age". Except, that is, for something that seemed to suggest that older maternal age at birth of child seemed to correlates with "improved sociability" in offspring. The authors report that their observations: "provide important insights into the apparent lack of a relationship between increasing parental age and increasing autism spectrum disorder phenotypic severity".

Of course one has to be careful with any study of correlation/association, particularly when it comes to something as simple as just looking at ATEC scores of severity of behaviours in the autism domains and parents age at time of birth of their children. I personally would also have liked to see some further discussion on whether the broader autism phenotype (BAP) for example, might have been an influencing variable too in light of studies like the one from Hasegawa and colleagues [6]. Also, the participant group is quite large - as the authors note - but even there I think back to the sort of sample numbers that those [big data] studies in Taiwan are including (see here) as to where we should be heading.

That all being said, I don't want to downplay the Geier results. Another quote might be useful here: "most observed de novo genetic events are unconnected to an autism spectrum disorder diagnosis, and those that do confer risk are distributed across many genes and are not necessarily sufficient for disease". This ties in rather nicely with the recent discussions on common variations and autism risk (see here) and how Gaugler and colleagues [7] questioned how much weight to give to de novo mutations in the grand scheme of autism 'causation'. This also might imply that non-genetic events, or at least non-structural genetic events headed under the general banner of environment might also play some contributory role to at least some cases of autism. Again, something which has cropped up on this blog before (see here).

Music to close. Given the recent vote near these parts, one of Scotland's most famous exports... Franz Ferdinand and Do You Want To.

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[1] Geier DA. et al. An Evaluation of the Effect of Increasing Parental Age on the Phenotypic Severity of Autism Spectrum Disorder. J Child Neurol. 2014 Aug 27. pii: 0883073814541478.

[2] Hooker B. et al. Methodological issues and evidence of malfeasance in research purporting to show thimerosal in vaccines is safe. Biomed Res Int. 2014;2014:247218.

[3] Hooker BS. Measles-mumps-rubella vaccination timing and autism among young african american boys: a reanalysis of CDC data. Transl Neurodegener. 2014; 3: 16.

[4] Kong A. et al. Rate of de novo mutations and the importance of father's age to disease risk. Nature. 2012 Aug 23;488(7412):471-5.

[5] Lampi KM. et al. Parental age and risk of autism spectrum disorders in a Finnish national birth cohort. J Autism Dev Disord. 2013 Nov;43(11):2526-35.

[6] Hasegawa C. et al. Broader autism phenotype in mothers predicts social responsiveness in young children with autism spectrum disorders. Psychiatry Clin Neurosci. 2014 Jun 6. doi: 10.1111/pcn.12210.

[7] Gaugler T. et al. Most genetic risk for autism resides with common variation. Nature Genetics. 2014. July 20.

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Geier DA, Hooker BS, Kern JK, Sykes LK, & Geier MR (2014). An Evaluation of the Effect of Increasing Parental Age on the Phenotypic Severity of Autism Spectrum Disorder. Journal of child neurology PMID: 25163730