Rate of first recorded diagnosis of autism and other pervasive developmental disorders in United Kingdom general practice, 1988 to 2001

Liam Smeeth,Peter G Smith,Professor Eric Fombonne,Lisa Heavey,Claire Cook,Laura C Rodrigues,Andrew J Hall

doi:10.1186/1741-7015-2-39

Liam Smeeth, Peter G Smith + Show 5 more

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BackgroundThere 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.MethodsWe 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.ResultsThe 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.ConclusionsBetter 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.

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There has been concern that the incidence of autism and other pervasive developmental disorders (PDDs) is increasing
The term pervasive developmental disorder (PDD) refers to a range of disorders with onset in childhood characterised by abnormalities in the domains of language development, communication abilities and social interactions and by a rigid, repetitive pattern of behaviours and interests [1]
Within PDDs, autism refers to children meeting full diagnostic criteria for the above three domains of developmental impairments and onset before the age of three years

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Introduction

There has been concern that the incidence of autism and other pervasive developmental disorders (PDDs) is increasing. The other PDDs are Asperger's syndrome (a less severe form of PDD with the features described above but without language delay and with intelligence within the normal range), pervasive developmental disorder not otherwise specified (not fulfilling complete criteria for autism), and childhood disintegrative disorder (a severe form of autism developing in previously normal children who undergo massive regression between the ages of 2 and 10 years) [2]. There is some evidence that increased prevalence rates are due to a broadening of the concept of PDD and changes in diagnostic practice [6,7] This has not gone unchallenged, and it is likely that increased awareness and changes in educational and social policies account for some of the recent upward trend in rates[6,8]. A real increase in the incidence cannot be ruled out [3]

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