Friday, 28 June 2013

Canada and the autism prevalence rate

[Update: 01/07/13: Further discussion on this topic can be found here].

The autism numbers game has been a long running discussion in many quarters. Even with estimates now suggesting that anywhere between 1 in 88 children or 1 in 50 children (or 1 in 57 if you prefer) in the United States (depending on who and how you count) might present with an autism spectrum condition, arguments still rage about the hows and whys, often over and above the question: 'what are we going to do about it'.
Waterloo Bridge @ Wikipedia 

I'm sitting on the fence a bit about why the numbers are increasing as they are. I appreciate that we are better at detecting autism than we were 30 or 40 years ago and all the related opinions about changes in diagnostic schedules (see here) and reclassification from other conditions in favour of the autism spectrum. There is little doubt that these factors exert an effect and are probably going to be significant ones.

Having said that though I'm not yet ready to give up on the idea that some of the increase in cases is due to other factors including being representative of a true and real increase in cases. My reasoning for this opinion is multi-faceted but includes the fact that we have, at least in the Western world, more than adequate provisions for the detection of [pediatric] autism and to say that its all about reclassification or awareness really brands our autism diagnosticians as being pretty incompetent over the years. They're not by the way; indeed they do a sterling job often in very, very difficult circumstances. What I should also point out is that the reasons for the increase might not necessarily be the same for every part of the world.

Just before also you tell me there is no evidence that the incidence - not prevalence - of autism is increasing, I beg to differ as per some of my previous posts which can be seen here and here. Indeed this leads into an interesting paper that has recently appeared by Hélène Ouelette-Kuntz and colleagues* on the prevalence rate of autism in several regions in Canada which forms the topic of this post.

I'll admit to not having the full-text of the Oueltte-Kuntz paper so you might need to do some further fact-checking on any conclusions that I reach. Actually, the chances are that I'm probably not going to reach any conclusions on the paper so maybe this is a moot point.

The first thing that we do get from the abstract to the paper is that based on an analysis of data from the National Epidemiologic Database for the Study of Autism (NEDSAC) (yes same author) autism prevalence is increasing in this study. That increase in annual prevalence ranges from 9.7% up to 14.6% I assume because of the differing prevalence rates among the different regions of Canada the study authors looked at.

The next thing to glean from the abstract are some of the reasons put forward to account for the increase: previously unidentified cases being identified and the issue of "in-migration" which concerns movement between regions of the same country/territory.

Finally, a quote: "we cannot rule out the possibility of a true increase in incidence, particularly given the lack of a leveling-off of prevalence among the 6- to 9-year olds". In other words, the door is still open to a 'real' increase in cases being contributory to the numbers.

I'm sure the arguments will continue about the hows and whys of the autism numbers game. One thing is abundantly clear from most of the emerging data: autism is fast becoming a 'common condition' as per another recent report on the autism numbers game from Evald Saemundsenand and colleagues** (open-access) and a particularly interesting table. As we stand at the moment, we don't really know all the reasons why and what to do about it.

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* Ouellette-Kuntz H. et al. The changing prevalence of autism in three regions of Canada. J Autism Dev Disord. 2013 Jun 16.

** Saemundsen E. et al. Prevalence of autism spectrum disorders in an Icelandic birth cohort. BMJ Open. 2013 Jun 20;3(6). pii: e002748. doi: 10.1136/bmjopen-2013-002748.

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ResearchBlogging.org Ouellette-Kuntz H, Coo H, Lam M, Breitenbach MM, Hennessey PE, Jackman PD, Lewis ME, Dewey D, Bernier FP, & Chung AM (2013). The changing prevalence of autism in three regions of Canada. Journal of autism and developmental disorders PMID: 23771514