Canada Announces Autism Prevalence Study Results – On Time and Going Up

April 05, 2018

While America’s attention has been focused on its southern border, our northern neighbors have announced the results of a Canadian autism prevalence study. The study received little attention in the U.S., despite its relevance to our situation here.

The study found the prevalence of an autism spectrum disorder among Canadian children to be 1 in 66, or 15.2 per 1000 children. The study results were announced on March 29 by the Public Health Agency of Canada, in time for World Autism Awareness Day on April 2. The survey data was collected in 2015 and covered 40% of the Canadian school-aged population ages 5-17. Seven of the 13 provinces/territories in Canada participated in the survey.

[Source: Canadian Broadcasting Company]

For 4 of the 7 Canadian provinces included in the study, 2015 was their first year of data collection. Three of the provinces, however, have collected prevalence data for many years. All three showed a steady increase in autism prevalence over time, as presented in the graph below. For example, Prince Edward Island reported a 5 per 1,000 rate in 2003 and a 17.7 per 1000 rate in 2015, or 3 1/2 times more autism in the space of 12 years. Similarly, Newfoundland and Labrador grew 3 1/4 times (from 6.0 in 2003 to 19.6 in 2015) and Quebec’s increase was 4 1/2 times (from 3.5 in 2003 to 15.7 in 2015).

[Source: Public Health Agency of Canada]

These increases parallel the alarming rise in autism reported here in the US, including data from California’s Department of Developmental Services and the US Department of Education’s IDEA Data System.

It is tempting to compare these new Canadian numbers with the U.S. numbers from our own public health agency, the Centers for Disease Control and Prevention (CDC), but caution is warranted.

The CDC last reported prevalence from its ADDM surveillance network in 2016. It gave a prevalence rate of 1 in 68, or 14.6 per 1000 children, close to Canada’s 1 in 66. The CDC was supposed to release their 2018 report last week, also in time for Autism Awareness Day. But they are late and not reporting for several weeks. The new autism rate could be different from the previous 1 in 68 or from Canada’s 1 in 66.

The reason is that the CDC’s ADDM methodology differs in many ways from Canada’s approach.

ADDM surveys collect records of 8 year olds, rather than all school ages (5-17), and prevalence varies by the age of the child, being lowest in the youngest and the oldest kids and highest in kids 8-12 according to a number of studies. Canada’s survey covers 40% of their child population across 7 of their 13 provinces/territories, whereas the US only covers 8.5% of its 8 year olds in just 11 of 50 states. As shown in both ADDM and Canadian studies, prevalence varies widely by data collection site. Canada counts children with a confirmed ASD diagnosis written in medical, educational or social services records, while the CDC infers an ASD case based on both diagnosis and indicated symptoms/behaviors contained in medical or educational records.

That methodology can make a big difference in results is shown by yet another U.S. Government study, this one from the National Center for Health Statistics. Its most recent survey in 2017 from interviews conducted in 2014-2016 reported a 1 in 36 autism rate. This study is a nationally representative sample, with interviews among parents of 3-17 year old children, asking: “Has a doctor or health professional ever told you that [sample child] had Autism, Asperger’s disorder, pervasive developmental disorder, or autism spectrum disorder?”

What is most noteworthy is that this study too has shown a rapid increase in the rate of autism, from 1 in 91 for the 2009 report for 2007 interviews to the current 1 in 36, or 2 1/2 times the earlier rate in just 10 years.

[Source: Age of Autism]

The main take-away from all these studies is that no matter the source, the place or the methodology, the rate of autism continues to climb. The causes of this increase must be found. The needs of the burgeoning autism population must be acknowledged and funded. Accurate counting of cases is critical to address both these issues.

The Canadian effort shows that more timely reporting and a more representative sample are possible for a large epidemiology study. The U.S. could do the same and more is if it were serious about addressing the crisis of autism. Living south of the border, we can only hope.

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