Preschool Speech Intelligibility and 8-Year Literacy: A Moderated Mediation Analysis

Purpose The aims of this study were (a) to examine the relationship between speech intelligibility at the age of 5 years and literacy skills at the age of 8 years, (b) to explore the possible mediating or moderating role of broader language skills at 5 years in the relationship of interest, and (c) to assess whether the potential risk factors (child gender; maternal education levels; and family history of speech, language, reading, and writing difficulties) influence the relationship between speech intelligibility and literacy in terms of moderated mediation effects. Method We used mother-reported questionnaire data on 16,184 children participating in the population-based, prospective Norwegian Mother, Father and Child Cohort Study as well as conducted linear regression analyses using the PROCESS macro in SPSS. In addition, logistic regression was conducted to make predictions about risk. Results The association between speech intelligibility at 5 years and literacy skills at 8 years was statistically significant (β = .168, p < .001). Children with speech problems at 5 years had a risk ratio of 2.38 (95% CI [2.10, 2.70]) and an odds ratio of 2.74 (95% CI [2.35, 3.19]), as compared to children without such problems. Broader language skills at 5 years partially mediated the relationship between speech intelligibility at 5 years and literacy at 8 years, and the effect of language skills appeared to be moderated by child gender, a family history of language difficulties, a family history of reading difficulties, and maternal education. Conclusions Severity of speech problems indexed by parent-reported speech intelligibility in preschool predicted school-age literacy problems. Broader language skills are a crucial mediating mechanism through which these problems are linked, and the mediated relationship is amplified by female gender, low maternal education, family history of language difficulties, and family history of reading difficulties. The findings call for increased use of a multiple-risk model when planning early interventions in children with unclear speech.