Outcomes of Early Language Delay

Abstract

Genes are known to play an important role in causing specific language impairment, but it is unclear how far a similar etiology is implicated in transient language delay in early childhood. Two-year-old children with vocabulary scores below the 10th centile were selected from a cohort of over 2,800 same-sex twin pairs whose language was assessed by parental report at 2, 3, and 4 years of age. These children with early language delay (ELD) were divided into cases of transient and persistent language difficulties on the basis of outcome at 3 and 4 years. A DeFries-Fulker analysis (J. C. DeFries & D. W. Fulker, 1985) was used to compute group heritability (h2g) of 2-year vocabulary delay separately for those with transient and persistent difficulties. When 3-year and 4-year language attainments were used to categorize outcomes, h2g was similar and modest (.25 or less) for both transient and persistent difficulties. However, when persistent difficulties were defined according to whether parents expressed concern about language at 3 years or according to whether a professional had been consulted about language difficulties at 4 years, heritability was significantly higher. For 289 children with no professional involvement at 4 years, heritability of 2-year vocabulary delay was close to zero, whereas for 134 children with professional involvement, a significant h2g of .41 (SE = .127) was found. Early language delay appears largely environmental in origin for 2-year-olds whose parents do not go on to seek professional help.

Early Language Delay Phenotypes and Correlation with Later Linguistic Abilities

“…Although toddlers of the TD group were coming typically from families with no history of language delays (79.2%), the LT group toddlers presented a marginally higher percentage of a family history with language delays. The significant contribution of familial aggregation in early developmental language disorders has been well documented and has been considered, but its role as a risk factor remains equivocal [18,32,34] even though our results did not support this argument. It is possible that in a larger sample of LTs and with the use of more sensitive tools in determining familial risk one might actually observe stronger predictive power.…”

“…Consequently, a delay in expressive vocabulary marks a universal linguistic tendency that needs to be taken into consideration regardless of linguistic and/or cultural variation. This pattern has served as the impetus for researchers to advance hypotheses related to neurodevelopmental and neurobiological maturation substrate that impacts early linguistic milestones [18,31]. …”

“…This line of research has yielded variable results and has not yet identified specific determinants of ongoing problems in these children. The fact that it has not been possible to reveal predictors of outcome for these children has led some researchers to suggest that children identified at 2 years of age on the basis of an expressive vocabulary delay do not constitute a homogeneous group [14,15,18]. That is, expressive vocabulary alone does not differentiate children who continue to show linguistic difficulties at some later developmental point.…”

“…Despite variability in identifying robust risk factors, familial history, socioeconomic status, level of receptive language skills and gender appear to be strong correlates of later language challenges [18,32,35]. A factor that has not been examined extensively in children with late onset of expressive vocabulary is the impact of a history of otitis media (OM) onto later language abilities.…”

“…Furthermore, research suggests that although many toddlers seem to grow out of this delay, thus forming a ‘late bloomers' group, the rest of the children continue to exhibit significant language and academic challenges [14,15,16,17]. Although many LT children achieve age-appropriate scores on standardized batteries by the age of 3-5 years, others continue to lag behind on a number of language milestones, as well as reading and academic challenges [18,19,20,21,22]. Specifically, language outcomes during the preschool years indicated significant progress for lexical development but impaired morphological, phonological and syntactic skills [23,24,25,26,27,28,29,30].…”