Short-term impact of preschool sound exposure on outer hair cell function in young children: An analysis using pressurised distortion product otoacoustic emissions

Abstract

Background Preschool children are regularly exposed to high noise levels that may affect hearing. A previous study has linked preschool noise exposure to reduced distortion product otoacoustic emission (DPOAE) amplitudes. Since DPOAEs primarily reflect outer hair cell (OHC) activity, they provide an indirect marker of cochlear function. Measurement accuracy can be affected by middle-ear pressure. Pressurised DPOAEs (pDPOAEs) compensate for middle-ear pressure during recording. Methods This cross-sectional study aimed to examine the relationship between preschool noise exposure and pDPOAE amplitudes while accounting for middle-ear pressure. Seventy-five children (4–6 years old) were monitored using dosimeters to measure the equivalent continuous sound level (LAeqTi) and the 95th percentile of maximum levels (LAFmax,95). Of these, 56 children completed pDPOAE testing at four time points during the preschool week. Linear mixed-effects models evaluated associations with noise exposure, time of day and progression across the week. Results For personal dosimetry, the mean LAeqTi was 80 dB (range: 60–98 dB) and the mean LAFmax,95 was 97 dB (range: 77–110 dB). Most LAeqTi levels (86.2%) were between 75–85 dB, with LAFmax levels exceeding 115 dB in 53.8% of the cases. No significant associations were found between LAeqTi or LAFmax,95 and pDPOAE amplitudes (p>0.05). Time-of-day differences were observed, with higher amplitudes in the afternoon at 4kHz (p=0.045) and 6kHz (p=0.047) in the right ear, and 3kHz in the left ear (p=0.021). Girls showed higher amplitudes than boys at 4kHz in the left ear (p=0.030). Conclusions Although pDPOAE amplitudes varied with time of day, and sex, a direct exposure–response relationship with preschool noise was not demonstrated. Short-term variations in typical preschool noise exposure may not measurably affect cochlear function in young children. Future research should refine exposure assessment and recording protocols to reduce variability and improve detection of small physiological changes.