A team from Stafford and London, England, investigated the prevalence of pervasive developmental disorders (PDDs), otherwise known as autism-spectrum disorders, in a geographically defined population of preschool children.
The researchers conducted a survey between July 1998 and June 1999 in Staffordshire, England.
15,500 children aged 2.5 to 6.5 years were screened for developmental problems.
A multidisciplinary team intensively assessed children with symptoms suggestive of a PDD. They conducted standardized diagnostic interviews and administered psychometric tests.
Prevalence estimates for the different subtypes of PDDs were made.
A total of 97 children (79.4% male) were confirmed to have a PDD.
The prevalence of PDDs was estimated to be 62.6 per 10,000 children.
The researchers found that prevalence was 16.8 per 10,000 for autistic disorder, and 45.8 per 10,000 for other PDDs.
|16.8 preschool autistic children per 10 000
The mean age at diagnosis was 41 months. Health visitors (nurse specialists) originally referred 81%.
Of the 97 children with a PDD, 25.8% had some degree of mental retardation and 9.3% had an associated medical condition.
Dr Suniti Chakrabarti, of the Child Development Centre, Central Clinic, Stafford, concluded on behalf of colleagues, "Our results suggest that rates of PDD are higher than previously reported.
"Methodological limitations in existing epidemiological investigations preclude interpretation of recent high rates as indicative of increased incidence of these disorders, although this hypothesis requires further rigorous testing.
"Attention is nevertheless drawn to the important needs of a substantial minority of preschool children."
In an accompanying editorial, Dr Susan Hyman, of Rochester, New York, USA, comments, "Chakrabarti and Fombonne have corroborated that PDDs are not rare among preschool children.
"Given the limitations of current knowledge, valuable data sets such as these should be used to increase understanding of the characteristics of young children with PDDs, as well as to determine the current prevalence."
"Accurate prevalence data will assist in planning for services that affected children and their families will need," she concludes.