Age at First Diagnosis of An Autism Spectrum Disorder in Different Regions of Canada

Background:

Early diagnosis of autism spectrum disorders (ASDs) reduces family stress, empowers parents to make choices such as seeking genetic counseling, and may lead to better treatment outcomes. There are no empirical data on the age at which Canadian children are first diagnosed with an ASD.

Objectives:

To examine: 1) the age at which children are first diagnosed with an ASD in different regions of Canada; 2) whether the age at diagnosis is decreasing; and 3) the association between specific factors and age at diagnosis.

Methods:

The data for this analysis were collected as part of a Canadian surveillance program for ASDs (National Epidemiologic Database for the Study of Autism in Canada: NEDSAC). Population-based surveillance of diagnosed cases of ASD among children has been ongoing since 2002 in Manitoba and Prince Edward Island (PEI), and since 2003 in Newfoundland/Labrador and Southeastern Ontario. From 2002 to 2007 data were also collected on children diagnosed with an ASD at three referral centres in Vancouver, British Columbia (BC), and from 2003 to 2006 on children with an ASD identified through various sources in Calgary, Alberta. The sample for this analysis included children living in one of the surveillance regions who were first diagnosed with an ASD between 1997 and 2005. For the first two objectives, we included data from Manitoba, Southeastern Ontario, PEI, and Newfoundland/Labrador. We used the Kruskal-Wallis test to compare age at diagnosis among regions, and the Spearman’s rank correlation to examine intra-regional trends by three-year period of initial diagnosis. We included data from all six geographic areas to examine factors related to age at diagnosis. Due to small cell counts for some variables in Calgary, Southeastern Ontario, PEI, and Newfoundland/Labrador, we pooled the data from those four regions (=four combined regions). The multiple imputation procedure in SAS was used to impute values for missing data, and generalized linear regression models were fit for BC, Manitoba, and the four combined regions.

Results:

There were significant differences in the age at first ASD diagnosis among the regions (p<.001), ranging from a median of 39 months in Newfoundland/Labrador to 55 months in Southeastern Ontario. No temporal decreases in age at diagnosis were found, and in Southeastern Ontario the age at diagnosis increased significantly (p=.004). Asperger disorder, PDD-NOS, birthplace outside Canada, being adopted, being female, and Aboriginal identity were all associated with a later age at diagnosis in one or more regions. No significant associations were found between age at diagnosis and urban/rural residence or household income.

Conclusions:

Our findings suggest that Canadian children with an ASD are not being diagnosed at as young an age as the literature suggests they could be. Future studies should include a broader range of factors that may affect age at diagnosis, such as waiting times for assessment. Such research will complement efforts to increase awareness of ASDs among parents and professionals, in the hopes that this will lead to earlier detection and access to treatment and support for children with ASDs and their families.