Estimation de la prévalence et du taux d’incidence du trouble du spectre de l’autisme (TSA). Comparaison interprovinciale Estimating the Prevalence and Incidence Rate of Autism Spectrum Disorder (ASD): Interprovincial Comparisons

Résumé

L’objectif de cet article est d’estimer la prévalence et le taux d’incidence du trouble du spectre de l’autisme (TSA) diagnostiqué chez les enfants et les adolescents à partir de données médico-administratives jumelées de quatre provinces canadiennes. Un objectif secondaire est de comparer les résultats obtenus afin d’établir si les fichiers administratifs peuvent servir de système d’information pour la surveillance du TSA au Canada.

Les estimations ont été produites à partir des données provenant des provinces du Manitoba, de l’Ontario, du Québec et de la Nouvelle-Écosse. La population à l’étude est composée de tous les résidents âgés de 24 ans et moins admissibles au régime d’assurance maladie en vertu de la loi provinciale entre 1999 à 2012. Pour être considéré comme ayant un TSA, l’individu devra avoir eu au moins une visite médicale ou une hospitalisation avec un diagnostic principal de TSA (codes 299 de la CIM-9 ou leurs équivalents CIM-10-CA). La prévalence annuelle et le taux d’incidence sont mesurés pour la période allant de 1999-2000 à 2011-2012, et présentés selon le sexe et par groupes d’âge.

La prévalence du TSA entre 1999 et 2012 a connu une forte progression dans toutes les provinces et pour tous les groupes d’âge. Le taux d’incidence a suivi la même tendance d’accroissement dans le temps. La prévalence et le taux d’incidence du TSA n’ont pas augmenté de façon similaire dans toutes les provinces du Canada. L’Ontario semble afficher les plus fortes proportions, suivi de la Nouvelle-Écosse.

Nos résultats permettent non seulement de dresser un portrait du TSA dans quatre provinces canadiennes, mais soulèvent aussi de nombreuses pistes pour de futures recherches. Cette étude discute également de l’utilité, de la fiabilité et du potentiel des fichiers médico-administratifs en matière de recherche.

Mots-clés :

• trouble du spectre de l’autisme,
• données médico-administratives,
• surveillance,
• prévalence,
• taux d’incidence

Abstract

Objective The prevalence of diagnosed autism spectrum disorders (ASD) has risen steadily over time. There is therefore a need for the monitoring of treated ASD for timely policy making. The objective of this study is to report and compare over a 10-year period the prevalence and incidence rate of diagnosed ASD in four Canadian provinces.

Methods This study utilized data from the provinces of Manitoba, Ontario, Quebec and Nova Scotia with access to linked administrative database sources used in the Canadian Chronic Diseases Surveillance Systems to assess the prevalence and incidence rate of a physician diagnosis of ASD. Estimates were produced using health datasets for outpatient and inpatient care (Med-Echo in Quebec, the Canadian Institute of Health Information Discharge Abstract Database in the three other provinces, plus the Ontario Mental Health Reporting System). Dates of service, diagnosis, and physician specialty were extracted. The target population consisted of all residents aged 24 and under eligible for healthcare coverage under provincial law between 1999 and 2012. To be considered as having ASD, an individual had to have at least one physician claim or hospital discharge abstract indicating one of the following: ICD-9 codes 299.0 to 299.9 or their ICD-10 equivalents, F84.0 to F84.9. The estimates were presented in yearly brackets between 1999-2000 and 2011-2012 by sex and age groups. The main analyses focused on those aged 17 years or less, with the 18 to 24 years group added to show the subsequent progression of the disorder.

Results Our findings show that the annual prevalence of ASD rose steadily between 1999 and 2012 in all provinces and for all age groups although this increase varied across Canadian provinces. There were higher annual prevalence estimates in Ontario (4.8 per 1,000) and Nova Scotia (4.2 per 1,000) compared to Quebec (3.0 per 1,000) and Manitoba (2.5 per 1,000), among persons aged 17 years and younger in 2011. As compared to 1999, Quebec and Ontario reported a fivefold and fourfold increase in 2010-2012, the highest among provinces. The prevalence was four times higher in boys than in girls. By age group, the highest prevalence was observed in those aged between 1 to 4 and 5 to 9 years depending on the province. ASD was generally diagnosed before age 10. Incident cases were more frequently diagnosed by pediatricians followed by either psychiatrists or general practitioners depending on the province.

Conclusion Our research confirms that ASD has risen steadily in terms of prevalence and incidence rate and that it varies considerably across provinces. It also demonstrates that health administrative databases can be used as registers for ASD. Information derived from these databases could support and monitor development of improved coordination and shared care to meet the continuous and changing needs of patients and families over time. Implication for future research include exploring the etiology of ASD in more recent cohorts as well as investigating the association between variations in health service availability and the prevalence of ASD.

Keywords:

• autism spectrum disorders,
• administrative databases,
• surveillance,
• prevalence,
• incidence rate