Trends in Special Education Code Assignment for Autism: Implications for Prevalence Estimates

There is considerable controversy over reasons for observed increases in the prevalence of autism spectrum disorders. We examined trends in British Columbia education database coding of children with autism from 1996 to 2004. There was a significant linear increase in autism prevalence. The proporti...

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Bibliographic Details
Published in:Journal of autism and developmental disorders 2007-11, Vol.37 (10), p.1941-1948
Main Authors: Ouellette-Kuntz, Helene, Coo, Helen, Lloyd, Jennifer E. V, Kasmara, Liza, Holden, Jeanette J. A, Lewis, Suzanne M. E
Format: Article
Language:English
Subjects:
Age
Age Factors
Autism
Autism Spectrum Disorders
Autistic Disorder - classification
Autistic Disorder - diagnosis
Autistic Disorder - epidemiology
Biological and medical sciences
British Columbia
Canada
Child
Child clinical studies
Child, Preschool
Coding
Cohort Studies
Cross-Sectional Studies
Current Procedural Terminology
Developmental disorders
Diagnostic and Statistical Manual of Mental Disorders
Education, Special - statistics & numerical data
Female
Females
Foreign Countries
Health Surveys
Home Schooling
Humans
Identification
Incidence
Infantile autism
Interpersonal Relationship
Male
Medical sciences
Mental Disorders
Partnerships in Education
Pervasive Developmental Disorders
Prevalence
Psychiatry
Psychology. Psychoanalysis. Psychiatry
Psychopathology. Psychiatry
School Districts
Sex Ratio
Special Education
Trend Analysis
Verbal Communication
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Summary:There is considerable controversy over reasons for observed increases in the prevalence of autism spectrum disorders. We examined trends in British Columbia education database coding of children with autism from 1996 to 2004. There was a significant linear increase in autism prevalence. The proportion of children identified by age 6 increased significantly from 1996 to 1999. When we calculated prevalence assuming onset prior to age 3, previously unidentified cases, particularly among girls in 1996 and 1997, accounted for substantial increases in estimated prevalence. The magnitude of under-identification decreased from 1996 to 2000, and rose slightly in 2001. Analyses of prevalence trends must take into account effects of earlier age at identification and inclusion of previously undetected cases on prevalence estimates.
ISSN:0162-3257
1573-3432
DOI:10.1007/s10803-006-0326-4