Pervasive developmental disorders in preschool children

Context Prevalence rates of autism-spectrum disorders are uncertain, and sp eculation that their incidence is increasing continues to cause concern. Objective To estimate the prevalence of pervasive developmental disorders ( PDDs) in a geographically defined population of preschool children. Design, Setting, and Participants Survey conducted July 1998 to June 1999 i n Staffordshire, England. The area's 15500 children aged 2.5 to 6.5 years w ere screened for developmental problems. Children with symptoms suggestive of a PDD were intensively assessed by a multidisciplinary team, which condu cted standardized diagnostic interviews and administered psychometric tests . Main Outcome Measure Prevalence estimates for subtypes of PDDs. Results A total of 97 children (79.4% male) were confirmed to have a PDD. T he prevalence of PDDs was estimated to be 62.6 (95% confidence interval, 50 .8-76.3) per 10000 children. Prevalences were 16.8 per 10000 for autistic d isorder and 45.8 per 10000 for other PDDs. The mean age at diagnosis was 41 months, and 81% were originally referred by health visitors (nurse special ists). Of the 97 children with a PDD, 25.8% had some degree of mental retar dation and 9.3% had an associated medical condition. Conclusions Our results suggest that rates of PDD are higher than previousl y reported. Methodological limitations in existing epidemiological investig ations preclude interpretation of recent high rates as indicative of increa sed 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.