Socioeconomic disadvantage is associated with prevalence of developmental language disorders, but not rate of language or literacy growth in children from 4 to 11 years: evidence from the Surrey Communication and Language in Education Study (SCALES)

Objectives. The purpose of this study was to determine the changing prevalence of developmental language disorders at different quintiles of the Income Deprivation Affecting Children Index (IDACI), a measure of neighbourhood deprivation. In addition, this study investigated the long term association of IDACI rank with growth in language and literacy skills for children with and without language disorder over a six year period.Design. Prospective, population-based, longitudinal cohort study.Setting. State-maintained primary schools in Surrey, England.Participants and procedure. Teachers rated the language skills of 7267 children starting a state-maintained school in 2011 (aged 4;9-5;10, 59% of all eligible children). Comprehensive language and literacy assessment was conducted with a monolingual sub-sample in Year 1 (n = 529, age 5-6), Year 3 (n = 499, age 7-8), and Year 6 (n = 384, age 10-11).Analytic methods. Logistic regression determined the association of IDACI scores and teacher-rated language proficiency. Structural Equation Models using auxiliary variables estimated the association of IDACI and prevalence of developmental Language Disorder (LD) in Year 1, and IDACI and language and literacy growth from Years 1 – 6.Results. Predicted probability of language disorder was 2.5 times greater at the 10th centile of IDACI rank (.19 [.11, .27]) versus the 90th centile (.07 [.04, .09]). IDACI rank did not associate with growth in raw scores on measures of vocabulary, grammar, or word reading. Socioeconomic gaps in vocabulary and grammar were ameliorated when language status at school entry was accounted for, but persisted for word reading. Conclusions. The association of neighbourhood disadvantage with language and literacy primarily reflects higher rates of language disorder in areas of socio-economic deprivation. Interventions that alleviate deprivation and enhance the language and literacy experiences of disadvantaged children could reduce socioeconomic attainment gaps. However, the persistence of language disorder suggests on-going support is required to attenuate personal and societal cost.