Evolution of the Auditory Environment of Hospitalized Very Preterm Infants in Relation to Room Type and Parental Presence

Background: Infants born very preterm (VP) display rapid brain development including the auditory cortex before term equivalent age (TEA). This critical period occurs in the neonatal intensive care unit (NICU), where meaningful auditory experiences can enhance brain development, while prolonged adverse exposure to noises and/or excessive silence may be detrimental.1 We examined the trajectories of auditory exposures of VP infants before TEA, and assessed implications of room type and parental presence.

Methods: We conducted a prospective study of infants born < 33 weeks’ gestational age in a hybrid design level-III NICU, where VP infants typically transition from single-family room (SFR) to semi-open bay (SOB) when they achieve medical stability. We used the Language Environment Acquisition (LENA) device to collect weekly auditory recordings of 16 hours for of up to 6 consecutive weeks for each infant. Room type (SFR vs SOB) and parental presence (6 hours or more vs less than 6) were documented at each measurement. We assessed the evolution of auditory exposures with advancing postmenstrual age (PMA) using repeated measure correlations. Results: We obtained 128 recordings among 25 VP infants. 73 measurements (57%) were performed in a SFR and 44 (34%) while parents were present 6 hours or more. The NICU auditory environment was predominantly composed of silence (53.2±27.4%), electronic sounds (19.0±18.9%), and noise (15.6±19.4%), while distant language (6.4±7.4%) and meaningful language (4.3±3.5%) represented the minority exposure. With advancing PMA, there was an increase in meaningful language (r = 0.54, p = 0.001) and a decrease in noise (r = -0.59, p<0.001) exposures. These trajectories continued as infants transitioned from SFR to SOB. The degree of exposure to meaningful language and adult word count appeared greater with high parental presence, especially before 37 weeks’ PMA. Conclusions: VP infants experienced primarily silence and undesirable exposures while in the NICU before TEA, with limited exposure to meaningful language. The increase in meaningful language and decrease in noise exposures with advancing PMA continued as infants transitioned to SOB. Higher parental presence appeared to coincide with more meaningful language and adult word count exposures in the earliest PMAs. Modifiable NICU environmental factors including architectural design and parental presence may play a role to optimize auditory experiences of VP infants before TEA. Bibliography: 1. Maitre NL, Key AP, Chorna OD, et al. The Dual Nature of Early-Life Experience on Somatosensory Processing in the Human Infant Brain. Curr Biol. 2017;27(7):1048-1054. doi:10.1016/j.cub.2017.02.036