As part of its epidemiological surveillance mission, Santé publique France estimates the prevalence of autism spectrum disorders at various administrative levels (national, regional, and departmental), tracks trends over time, and helps inform the general public and healthcare professionals.

Epidemiological Surveillance of Autism

Several factors contribute to the complexity of epidemiological surveillance of ASD and the estimation of prevalence: the heterogeneity of clinical presentations, a diagnosis that is exclusively clinical and may be made late, the diversity of care approaches, and changes in diagnostic criteria and classifications.

Disparities in prevalence rates

In international studies, there is significant heterogeneity in prevalence figures. The vast majority of studies originate from North America and Europe. As in France, various methodologies have been used for data collection: administrative data (school records, applications for social assistance, etc.), surveys with standardized measures sometimes combined with a clinical examination, or registry data. Generally, studies relying solely on administrative data report lower prevalence rates than those using a diagnostic procedure specific to the survey.

Numerous methodological factors contribute to the observed disparity in prevalence rates, the main ones being:

• the nature of the data sources;

• data collection methods;

• the age of the children included in the studies;

• the definitions and classifications of disorders (expansion of diagnostic categories in international classifications over time);

• the resources allocated for the identification, diagnosis, and care of affected children;

• the allocation of specific resources to increase the availability of referral and care facilities for children (which may lead to overdiagnosis to facilitate access to financial assistance and/or institutional care).

Specific epidemiological networks

In North America, there are specific epidemiological surveillance systems for ASD:

• In the United States, an epidemiological surveillance system was established in 2000 in 11 states by the Centers for Disease Control and Prevention (CDC) through the Autism and Developmental Disabilities Monitoring (ADDM) network. Very similar to the one established by the French registries of childhood disabilities, this network regularly produces prevalence estimates and descriptions of the characteristics of 8-year-old children with ASD. In 2014, the prevalence of ASD was estimated at 168 per 10,000 8-year-old children (or one in 59 children), with a male-to-female prevalence ratio of 4.0.

• The Public Health Agency of Canada recently established a national ASD surveillance system, the SNSTSA, initially focused on children and adolescents aged 5 to 17. This system uses several complementary data sources: records from the education and health sectors; review of these records by trained clinicians who confirm the diagnosis; survey data collected using an established methodology; and finally, analysis of administrative databases to document access to health care, education, or social services. The 2018 report presents the results of the analysis of 2015 data from seven of the 13 provinces and territories, covering 40% of Canada’s population of children and adolescents aged 5 to 17. It reports, for the year 2015, a prevalence of ASD of 152 per 10,000 children and adolescents in this age group, and 159 per 10,000 8-year-olds, with a male-to-female prevalence ratio of approximately 4.

In France, published prevalence rates have, since the 1990s, been primarily documented through the two French registries of childhood disabilities.

The French registries of childhood disabilities

The 1990s saw the creation of two population-based registries on childhood disabilities: the Registry of Childhood Disabilities and Perinatal Observatory (RHEOP), established in 1991 in Isère, Savoie, and Haute-Savoie, and the Registry of Childhood Disabilities of Haute-Garonne (RHE31), established in 1999.

Using a common methodology, these registries conduct epidemiological surveillance of childhood disabilities by actively identifying cases of children diagnosed with PDD during their eighth year of life.

The estimates produced in this way, while extremely valuable, are nevertheless limited to the geographic areas covered by these registries and to children in their eighth year of life.

To learn more about the Haute-Garonne Childhood Disabilities Registry (RHE31): https://rhe31.org/

To learn more about the Child Disability Registry and Perinatal Observatory (RHEOP):

North American estimates are currently the highest among all estimates cited in a recent review of the English-language literature by Fombonne et al. (2019). According to these authors, the results of recent studies yield an overall average figure of 69.0 per 10,000 (median = 61.9), corresponding to 1 in 145 children, which can be used as a current estimate of PDD/ASD.

The prevalence estimated by Santé publique France based on SNDS data (74 per 10,000 among 7-year-olds, or 1 in 136 children) is very close to this average figure.

ELENA: A French Cohort for Research

ELENA is a prospective, multicenter cohort of children with autism established in 2012. The children, who were under 16 years of age at the time of enrollment, have a diagnosis of ASD rigorously established in specialized centers. The primary objective is to study the developmental trajectories of these children and their determinants across multiple dimensions. The extensive data collection covers clinical, psychological, social, biological, and environmental variables. The ELENA cohort (Longitudinal Study of Children with Autism: http://elena-cohorte.org/) is supported by a multidisciplinary team linked to networks of clinicians and researchers in France and abroad.

See also:

van Bakel MM, Delobel-Ayoub M, Cans C, Assouline B, Jouk PS, Raynaud JP, et al. Low but increasing prevalence of autism spectrum disorders in a French area based on registry data. J Autism Dev Disord. 2015;45:3255-61.

Delobel M, Van Bakel ME, Klapouszczak D, Vignes C, Maffre T, Raynaud JP, et al. Prevalence of autism and other pervasive developmental disorders: data from French population registries. Generations 1995–2002. Neuropsychiatry of Childhood and Adolescence. 2013;61(1):23-30.

Vignes C, van Bakel M, Delobel M, Klapouszczak D, Arnaud C, Cans C. Prevalence of autism and other pervasive developmental disorders: data from French population registries. Generations 1995-2000. 2011.

Bejaoui B, Delobel M, Carroussel L, Cans C, Arnaud C. Prevalence of autism and other pervasive developmental disorders: Literature review (2000-2009). 2010.

Fombonne E, Myers J, Chavez A, Presmanes Hill A, Zuckerman K. Epidemiology of autism: where do we stand? Enfance. 2019;1:13-47.