Thursday, 25 October 2012

Allergic and autoimmune diseases and autism

Comorbidity is quite a big topic of interest to me. Specifically comorbidity when talking about autism or schizophrenia or quite a few other behaviourally-defined conditions.

Venn-ting @ Wikipedia 
The reason for my interest? Well let's just say that although many a textbook so report, autism for example is not just the sum of its triad (soon to be dyad) of symptoms but much, much more.

That and the fact that based on the current data as it stands, a diagnosis of autism is seemingly protective of nothing and indeed, often significantly increases the risk that one or more of quite a few other conditions can appear alongside.

I've talked about comorbidity quite a few times on this blog (significantly over-represented... and all that) but am drawn back into this area again following the paper from Mu-Hong Chen and colleagues* describing the allergic and autoimmune comorbidity present in autism based on quite a large participant group.

OK you can perhaps see why I might be interested in this paper given the words 'allergy' and 'autoimmunity' in the title and some link back to previous posts (see here and here). Autoimmunity in particular, is something which I personally think is severely under-rated when it comes to conditions manifesting behavioural and developmental aspects, given the more traditional somatic associations that have been made. But that's just my thoughts...

Anyhow, a few details about the Chen paper:

  • Quite a big study based on finding cases of autism (N=1596) among a National Health Insurance Database in Taiwan between 1996 and 2010. 
  • Autism cases were compared (1:4 ratio) with age and gender-matched asymptomatic controls for the presence of various allergic and autoimmune-defined conditions.
  • Results: various allergy and atopic diseases were more readily associated with autism cases than controls including allergic rhinitis, atopic dermatitis and asthma (odds ratios between 1.7-1.5). That added to quite a bit more frequency in autoimmune conditions such as type 1 diabetes (OR=4) and Crohn's disease (OR=1.46). Please note I've not included confidence intervals (CIs) (look them up in the paper if you're interested).
  • The authors conclude that there might be some important associations and potentially shared underlying mechanisms between these very somatically defined comorbidities and autism.

I've talked previously about autism in Taiwan on this blog. That post was with reference to some data on the numbers of cases of autism being detailed in Taiwan and how even outside of Europe and North America, autism rates seem only to be going in one direction: up. I'm not wishing to get into any deep conversations about why they might be going up - see the post on the CDC figures - but rather that they are and what implications this might have for lots and lots of people and services right across the globe.

This new data whilst retrospective and reliant on formal recorded diagnoses pretty much confirms what is already out there in the autism research literature. Type 1 diabetes has again been something I've discussed before with autism in mind and cumulatively suggest that this is something that should be considered for testing when a diagnosis of autism is given. I'm not by the way suggesting everyone with autism has diabetes, merely that the possibility of a greater risk should be considered.

Same thing goes for the Crohn's disease overlap, accepting that chatter about inflammatory bowel diseases and autism is a little bit more of a controversial area (should I mention gastrointestinal symptoms...) and perhaps links into a few more recent findings on things like gut permeability and gut bacteria (speculatively). The allergy/atopy side of things is also something which needs to be looked at with greater assiduity bearing in mind where conditions like asthma may eventually lead.

I can't really say too much more about this study and its implications. Harking back to the opening sentence of this post, comorbidity is quite a big area of interest for me. Judging by these and other results, perhaps we need to really start looking at just how important it might be to at least some cases of autism.

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* Chen MH. et al. Comorbidity of allergic and autoimmune diseases in patients with autism spectrum disorder: A nationwide population-based study. Research in Autism Spectrum Disorders. 2013; 7: 205-212.

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ResearchBlogging.org Chen, M., Su, T., Chen, Y., Hsu, J., Huang, K., Chang, W., Chen, T., & Bai, Y. (2013). Comorbidity of allergic and autoimmune diseases in patients with autism spectrum disorder: A nationwide population-based study Research in Autism Spectrum Disorders, 7 (2), 205-212 DOI: 10.1016/j.rasd.2012.08.008