title: Rate of first recorded diagnosis of autism and other pervasive developmental disorders in United Kingdom general practice, 1988 to 2001.
abstract: BACKGROUND
  There has been concern that the incidence of autism and other pervasive developmental disorders (PDDs) is increasing. Previous studies have been smaller, restricted to autism (excluding other pervasive developmental disorders such as Asperger's syndrome), included boys only, or have not been based on a national sample. We investigated time trends in the rates of diagnosis of pervasive developmental disorders.
  
  
  METHODS
  We analysed the rates of first diagnosis of pervasive developmental disorders among people registered with a practice contributing to the United Kingdom General Practice Research Database during the period 1988 to 2001. We included 1410 cases from over 14 million person-years of observation. The main outcome measures were rates of diagnosis of pervasive developmental disorders by year of diagnosis, year of birth, gender and geographical region.
  
  
  RESULTS
  The rate increased progressively from 0.40/10,000 person-years (95% CI 0.30 to 0.54) in 1991 to 2.98/10,000 (95% CI 2.56 to 3.47) in 2001. A similar change occurred in the age standardised incidence ratios, from 35 (95% CI: 26-47) in 1991 to 365 (95% CI: 314-425) in 2001. The temporal increase was not limited to children born during specific years nor to children diagnosed in a specific time period. The rate of diagnosis of PDDs other than autism rose from zero for the period 1988-1992 to 1.06/10,000 person-years in 2001. The rate of diagnosis of autism also increased but to a lesser extent. There was marked geographical variation in rates, with standardised incidence ratios varying from 66 for Wales to 141 for the South East of England.
  
  
  CONCLUSIONS
  Better ascertainment of diagnosis is likely to have contributed to the observed temporal increase in rates of diagnosis of PDD, but we cannot exclude a real increase.
authors.affiliation: Department of Epidemiology and Population Health, London School of Hygiene and Tropical Medicine, Keppel Street, London WC1E 7HT, UK. liam.smeeth@lshtm.ac.uk
authors.forename: Liam
authors.initials: L
authors.lastname: Smeeth
authors.forename: Claire
authors.initials: C
authors.lastname: Cook
authors.forename: Professor Eric
authors.initials: PE
authors.lastname: Fombonne
authors.forename: Lisa
authors.initials: L
authors.lastname: Heavey
authors.forename: Laura C
authors.initials: LC
authors.lastname: Rodrigues
authors.forename: Peter G
authors.initials: PG
authors.lastname: Smith
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Hall
mesh_terms: D020817:Asperger Syndrome / Q000175:diagnosis / Q000453:epidemiology; D001321:Autistic Disorder / Q000175:diagnosis / Q000453:epidemiology; D016022:Case-Control Studies; D016009:Chi-Square Distribution; D002648:Child; D002659:Child Development Disorders, Pervasive / Q000175:diagnosis* / Q000453:epidemiology; D005260:Female; D006801:Humans; D015994:Incidence; D008297:Male; D013997:Time Factors