Canada and the prevalence and incidence rates of autism (again)

"During the period from 2004 to 2015, both prevalence and incidence rates of diagnosed ASD [autism spectrum disorder] in preschoolers and toddlers residing in Manitoba increased significantly."

That was the conclusion reached in the paper by Amani Hamad and colleagues [1] who undertook analysis of the Manitoba Population Research Data Repository to examine "the annual prevalence and incidence rate of ASD between 2004 and 2015 in children aged 1 to 5 years residing in Manitoba." Such research follows quite a longstanding theme, where Canada is quietly producing some important information about the growth of autism across its population (see here and see here).

I mentioned two words in the title of this post - prevalence and incidence - which perhaps need further explanation. Prevalence refers to the number of existing cases of a condition / disorder / disease, typically expressed as a proportion of a population. Incidence is more about the number of new cases of a condition / disorder / disease during a specific period of time. Hamad et al reported data on both measures, where "1685 ASD cases were diagnosed between 2004 and 2015."

So: "The crude ASD prevalence increased from 0.46% in 2004 to 0.97% in 2015" and "The crude incidence rate increased from 0.16% in 2004 to 0.39% in 2015." These combined findings illustrate that the number of cases of diagnosed autism in young children in Manitoba over the period of 2004 and 2015 was not static; more and more people were being diagnosed, and with an increasing rate of diagnosis.

What's more to say? Well this data puts another nail in the coffin to the old 'autism isn't increasing' argument that has slowly fizzled out over the past decade or so. Autism diagnoses are on the increase; and as per the Hamad focus - preschoolers and toddlers - at least some of the increase is in the young and not just older children and adults who might have 'slipped through the diagnostic net'. Next questions: why and what? Why is autism still on the increase? What factors are driving the increase? And please, enough with the 'increasing awareness' dogma on this question...

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[1] Hamad AF. et al. Annual trends in prevalence and incidence of autism spectrum disorders in Manitoba preschoolers and toddlers: 2004-2015. Can J Public Health. 2019 Feb 11.

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Estimated autism prevalence in Canada in 2015: 1 in 66

"On March 29, 2018, the Public Health Agency of Canada published the first comprehensive review of the prevalence of autism spectrum disorder (ASD) in Canada."

So began the 'what did we find' summary (see here) covering the "Made in Canada" findings detailed in the Canadian National Autism Spectrum Disorder Surveillance System (NASS) 2018 Report (see here) [1]. Pertinent to the year 2015 and including some 88% of the children and young adults living in various participating Provinces and Territory, data was gathered from various sources (education, social services, health) onward to the estimated prevalence of diagnosed autism in Canada.

Their results: "Among children and youth 5–17 years old across seven provinces and territory, the combined prevalence of ASD for the year 2015 is 1 in 66 (15.2 per 1,000)" (bold text added by me).

Details, details, details... Such an estimate applies to children and young adults (youth) diagnosed with autism and does not say anything about the number of adults diagnosed with autism. It only covers those diagnosed with autism based on strict criteria: "The diagnosis of ASD is provided or confirmed by a licensed health care professional(s)... [and] The diagnosis of ASD is based on the clinical criteria in the Diagnostic and Statistical Manual (DSM) for Mental Disorders or the case is identified as ASD in the International Classification for Diseases (ICD)." It does not provide any information on how many people *might* be autistic but not yet in receipt of a diagnosis. Males made up the lion's share of those diagnosed. Most had been diagnosed by the age of 8 years (72%). Oh, and not every Province or Territory showed the same estimated prevalence rate for various potential reasons. And rest.

Also pretty important to the reported findings is the comparison with earlier years estimates: for 3 geographic locations in Canada we see the characteristic 'upward trend' in the estimated prevalence of ASD noted in other sample data from other countries, from around 4-6 per 1,000 in 2003 to between 16-20 per 1,000 in 2015. And when compared with a neighbour to the South (USA) and their estimated autism prevalence stats covering 2012 (see here) coming up with a figure of 1 in 68, the Canadian estimates are not a million miles away,. This, bearing in mind, some differences in the way the different country figures were arrived at and also the time periods covered. That also reminds me, we should be seeing the latest US stats on estimated autism prevalence from the CDC at some point in the (very) near future, and the promise that "the ADDM Network will be able to estimate ASD case status on the basis of both DSM-5 and DSM-IV-TR." Those comparisons should be rather interesting in light of other preliminary data (see here).

What else it there to say? Diagnosed autism is fairly prevalent across Canada (who have some important history in relation to the autism 'numbers game') and I assume we'll be seeing more on their tracking of the diagnosis in future times. Preparation is an important part of the figures being discussed; preparation of education, social and health services to support the numbers of children and young adults being diagnosed now and who, I assume, will eventually be transitioning to adult services. And on the topic of adult services, I'll refer you to Harold Doherty's blog and some of his opinions on adult services in a Canadian setting (see here).

Finally, is the question of 'why' the increase? Well, let's wait and see what those US CDC figures say first and how useful they might be to answering 'why' in the Canadian and other contexts too. I say this accepting that those 'better awareness', 'diagnostic switching' and 'broader criteria' arguments that have long been trumpeted as 'fact' are probably not all there is to see in this area (see here and see here).

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[1] Autism Spectrum Disorder among children and youth in Canada 2018. Public Health Agency of Canada. 2018. March 2018.

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Canada and the autism prevalence rate (yet again)

"At the end of 2013, the prevalence among children born in 2006 was 1 case of autism spectrum disorder per 46 children or 215.77 per 10 000."

That was the conclusions reached in the study by Lorine Pelly and colleagues [1] looking at "the incidence and 1-year cohort prevalence for autism spectrum disorders in children less than 15 years of age and living in the Avalon Peninsula at the time of diagnosis." The Avalon Peninsula by the way, is located in Canada.

Looking at data derived from the "Janeway Children’s Health and Rehabilitation Centre (St. John’s)" and specifically information pertinent to those with autism (this facility is apparently "the only child development centre in the region and is the only centre giving comprehensive autism spectrum disorder diagnoses to patients in this region") researchers set about looking at the numbers for autism diagnosis in the area. Autism spectrum disorder (ASD) diagnoses were based on DSM-IV criteria, confirmed through "multiple observations" and in most instances, involved data derived from the gold-standard assessment instrument that is ADOS (Autism Diagnostic Observation Schedule). Incidence and prevalence analyses were both undertaken.

So: "Between 2006 and 2010, 272 new cases of autism spectrum disorder were diagnosed within the study population." Most of these cases were male, and, get this, the median age of diagnosis was... 3.84 years. The lion's share of cases were autistic disorder (~47%) followed by autism spectrum disorder (27%) and then Asperger syndrome (20%). Complementing those diagnostic divisions and age at diagnosis was the fact that a module 1 ADOS was used for over 40% of assessments. The calculated incidence for 2006 was 10.1 per 10,000. This increased to 16.7 per 10,000 in 2010. The difference was statistically significant. Prevalence, as I've already said, was 1 in 46 in this cohort with males shouldering the largest risk.

Then, another important point emerges: "Our review found that many patients had at least one of the co-morbidities often associated with autism; the most prevalent were behavioural issues (n = 28), attention-deficit/hyperactivity disorder (n = 27) and anxiety disorder (n = 25)." It all sounds very ESSENCE-like if you ask me.

These are interesting data and add to previous studies looking at the autism numbers game in Canada (see here and see here). In that instance as in this, the numbers were increasing for whatever reason(s) and starting to look similar to the top-end CDC estimates from last year (2014). Pelly et al don't go into the specific hows and whys potentially linked to the increase in cases so I can't comment too much on that angle in their paper. Other recent publications talking about diagnostic substitution as one possible factor [2] in the increasing rate of autism makes a valid point but I dare say that things aren't so simple when it comes to the reasons behind the increase in different parts of the world [4]. Whether also such a increased rate of autism merits the term 'epidemic' is another issue covered recently in another paper [3] although I'm not getting too involved in that debate.

Music: Gossip - Standing In The Way Of Control.

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[1] Pelly L. et al. Incidence and cohort prevalence for autism spectrum disorders in the Avalon Peninsula, Newfoundland and Labrador. CMAJ Open. 2015. July 29.

[2] Polyak A. et al. Comorbidity of intellectual disability confounds ascertainment of autism: Implications for genetic diagnosis. Am J Med Genet B Neuropsychiatr Genet. 2015 Jul 22.

[3] Lilenfeld SO. et al. Fifty psychological and psychiatric terms to avoid: a list of inaccurate, misleading, misused, ambiguous, and logically confused words and phrases. Front. Psychol. 2015. August 3.

[4] Randall M. et al. Autism spectrum disorder: Presentation and prevalence in a nationally representative Australian sample. Aust N Z J Psychiatry. 2015 Aug 17. pii: 0004867415595287.

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Pelly, L., Vardy, C., Fernandez, B., Newhook, L., & Chafe, R. (2015). Incidence and cohort prevalence for autism spectrum disorders in the Avalon Peninsula, Newfoundland and Labrador CMAJ Open, 3 (3) DOI: 10.9778/cmajo.20140056