Effects of Home Literacy Environment and Home Physical Environment on Expressive Language Development of Children: Systematic Review and Population-based Data Analysis

Abstract

Background Expressive language development is integral to shape and fulfil potential from infancy onwards. Not only Home Literacy Environment (HLE) but also Home Physical Environment (HPE) have been related to the development of children, and understanding these relationships may bring us an opportunity to facilitate the language development of children. Aim The study investigates the effect of HLE and HPE on expressive language development at the age of two years. Methods This thesis has two parts. Part I is a systematic review of published studies, which assessed the effects of HLE and HPE on expressive language development of children under three years age. Part II presents the secondary data analyses of the records of 5960 cohort children who participated in the Growing Up in New Zealand (GUINZ) study. Longitudinal associations between HLE and the language outcome, and between HPE and the language outcome were explored. The interaction effects of HLE and HPE on the language outcome were then investigated using multivariate regression models. Results Part I: We identified 21 studies that examined the association between HLE and the language outcome, and a study that assessed the association between household heating and the language outcome. We, however, did not find any study that examined the interaction effect of HLE and HPE on the language outcome. Part II: In the secondary data analyses, there were significant positive associations between HLE and the language outcome. There was also a significant association between some measures of HPE such as the level of crowding and household heating, and the language outcome. There was a dose-response relationship between the composite measure of HLE and HPE, and the language development, but the interaction effect was not detected. Media exposure and the number of languages spoken significantly influenced the association between HLE and the language outcome. Conclusion The findings highlight the importance of HLE and HPE in shaping language development at the age of two years in New Zealand. Future research is required to better understand the complex associations between home environments and language development.