Outcomes of early language delay: I. Predicting persistent and transient language difficulties at 3 and 4 years.
Dale PS., Price TS., Bishop DV., Plomin R.
Parent-based assessments of vocabulary, grammar, nonverbal ability, and use of language to refer to post and future (displaced reference) were obtained for 8,386 twin children at 2 years of age. Children with 2 year vocabulary scores below the 10th centile were designated the early language delay (ELD) group, and their outcomes at 3 and 4 years were contrasted with the remainder of the sample, the typical language (TL) group. At 3 and 4 years old, children were designated as language impaired if their scores fell below the 15th centile on at least 2 of the 3 parent-provided language measures: vocabulary, grammar, and use of abstract language. At 3 years, 44.1% of the ELD group (as compared to 7.2% of the TL group) met criteria for persistent language difficulties, decreasing slightly to 40.2% at 4 years (as compared to 8.5% of the TL group), consistent with previous reports of frequent spontaneous resolution of delayed language in preschoolers. Although relations between language and nonverbal abilities at 2 years and outcome at 3 and 4 years within the ELD group were highly statistically significant, effect sizes were small, and classification of outcome on the basis of data on 2-year-olds was far too inaccurate to be clinically useful. Children whose language difficulties persisted were not necessarily those with the most severe initial difficulties. Furthermore, measures of parental education and the child's history of ear infections failed to substantially improve the prediction.