title: Incidence of autism spectrum disorders in children in two Australian states.
abstract: OBJECTIVE
  To ascertain the incidence of autism spectrum disorders in Australian children.
  
  
  METHODS
  New South Wales (NSW) and Western Australia (WA), July 1999 to December 2000.
  
  
  METHODS
  Data were obtained for WA from a prospective register and for NSW by active surveillance.
  
  
  METHODS
  Newly recognised cases of autism spectrum disorders (defined as autistic disorder, Asperger disorder and pervasive developmental disorder not otherwise specified [PDD-NOS]) in children aged 0-14 years; incidence was estimated in 5-year age bands (0-4 years, 5-9 years, 10-14 years).
  
  
  RESULTS
  In WA, 252 children aged 0-14 years were identified with autism spectrum disorder (169 with autistic disorder and 83 with Asperger disorder or PDD-NOS). Comparable figures in NSW were 532, 400 and 132, respectively. Most children were recognised with autistic disorder before school age (median age, 4 years in WA and 3 years in NSW). Incidence of autistic disorder in the 0-4-years age group was 5.5 per 10,000 in WA (95% CI, 4.5-6.7) and 4.3 per 10,000 in NSW (95% CI, 3.8-4.8). Incidence was lower in older age groups. The ratio of all autism spectrum disorders to autistic disorder alone was 1.5:1 in WA and 1.3:1 in NSW, and rose with age (1.8:1 and 2.9:1 in 10-14-year-olds in WA and NSW, respectively).
  
  
  CONCLUSIONS
  These are the first reported incidence rates for autism for a large Australian population and are similar to rates reported from the United Kingdom. Ongoing information gathering in WA and repeat active surveillance in NSW will help to monitor any future changes.
authors.affiliation: Children's Hospital at Westmead, Sydney, NSW. katrinaw@chw.edu.au
authors.forename: Katrina
authors.initials: K
authors.lastname: Williams
authors.forename: Emma J
authors.initials: EJ
authors.lastname: Glasson
authors.forename: John
authors.initials: J
authors.lastname: Wray
authors.forename: Marshall
authors.initials: M
authors.lastname: Tuck
authors.forename: Megan
authors.initials: M
authors.lastname: Helmer
authors.forename: Carol I
authors.initials: CI
authors.lastname: Bower
authors.forename: Craig M
authors.initials: CM
authors.lastname: Mellis
mesh_terms: D000293:Adolescent; D017677:Age Distribution; D020817:Asperger Syndrome / Q000453:epidemiology; D001321:Autistic Disorder / Q000453:epidemiology; D002648:Child; D002659:Child Development Disorders, Pervasive / Q000453:epidemiology*; D002675:Child, Preschool; D005260:Female; D006801:Humans; D015994:Incidence; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D009517:New South Wales / Q000453:epidemiology; D014904:Western Australia / Q000453:epidemiology