The prevalence, stability and significance of developmental language delay in preschool children.

A sample of 937 children in Dunedin, New Zealand, was assessed at ages three and five years in order to estimate the nature, prevalence, stability and significance of developmental language delays in three-year-olds. Assessments included language development, intelligence, and fine and gross motor-co-ordination. Detailed results are given which described three types of language delay at age three: delayed verbal comprehension only, delayed verbal expression only, and delayed development in both aspects of language. Follow-up testing at age five indicated that the specific language delays were not highly stable, whereas delays in both aspects were highly stable. A large proportion of the latter children gained very low scores on the measures at age five, and they accounted for 84 per cent of all children with very low intelligence. The implications of the results for a screening programme to identify three-year-old children at high risk of later developmental delays are considered.