Language Exposure of Preterm Infants in the Neonatal Unit: A Systematic Review

Background: Elevated sound levels and low language exposures of preterm infants (< 37 weeks) cared for in the neonatal unit contribute to poorer growth, cognition, language and motor outcomes. These delays can have lasting effects on childhood development and continue throughout adult life. Whilst recommendations have been established for appropriate sound exposure levels in neonatal units, very little is known about the optimal level of language exposure. Objectives: To examine the evidence regarding language exposure, both measured (observational) and prescribed (interventional), in preterm infants (< 37 weeks) cared for in neonatal units and to identify optimal exposure levels to promote neurodevelopment. Search Methods: An electronic search of English-language articles with an open date range was conducted in the PubMed, MEDLINE, Joanna Briggs, CINAHL and Cochrane databases and in Google Scholar. The criteria were limited to original research studies of preterm infants (< 37 weeks) in which language was either measured as it naturally occurred in the neonatal unit environment or through a language intervention. Results: The search produced a total of 2,367 articles, 49 of which were related to language. A full-text review of these articles identified 10 eligible studies and 6 studies from reference searches. Conclusions: Preterm infants experience low levels of language exposure and high sound exposures in neonatal units. There is a lack of conclusive evidence to recommend an optimal level of language exposure to support improved neurodevelopmental outcomes in preterm infants. Further research from large, good-quality clinical trials is required before clear direction can be provided to inform clinical practice.