%0 Journal Article
%T Noise-Induced Hearing Threshold Shift Correlated with Body Weight and External-Ear Amplification in Chinchilla: a Preliminary Analysis.
%A Grinn SK
%A Trevino M
%A Lobarinas E
%J J Assoc Res Otolaryngol
%V 24
%N 6
%D 2023 Dec 27
%M 38010580
%F 3.263
%R 10.1007/s10162-023-00913-2
%X <B>BACKGROUND: </B>External-ear amplification (EEA) has been shown to vary from 5-19 dB-A in large datasets of pediatric, adolescent, and adult human participants. However, variable EEA is an overlooked characteristic that likely plays a role in individual noise-induced hearing loss (NIHL) susceptibility. A noise exposure varying 5-19 dB-A translates to high-EEA individuals theoretically experiencing 3-4 times greater NIHL risk than low-EEA individuals.<BR><B>OBJECTIVE: </B>The purpose of this preliminary analysis was to test the hypothesis that higher EEA is correlated with increased noise-induced threshold shift susceptibility.<BR><B>METHODS: </B>Nine chinchillas were exposed to 4-kHz octave-band noise at 89 dB-SPL for 24 h. Auditory brainstem response thresholds were obtained pre-exposure, 24-h post-exposure, and 4-week post-exposure. Relationships between EEA and threshold shift were analyzed.<BR><B>RESULTS: </B>Open-ear EEA ranged 11-19 dB-SPL, and occluded-ear EEA ranged 10-21 dB-SPL. Higher occluded-ear EEA was correlated with increased NIHL susceptibility (p = 0.04), as was lower body weight (p = 0.01). Male animals exhibited more threshold shift than female animals (p = 0.02), lower body weight than female animals (p = 0.02), and higher occluded-ear EEA (male mean = 18 dB; female mean = 15 dB).<BR><B>CONCLUSIONS: </B>Taken together, increased threshold shift susceptibility was observed in the smallest animals, animals with the highest occluded-ear EEA, and in male animals (which tended to have higher occluded-ear EEA). Given the established relationship between smaller body size and higher occluded-ear EEA, these preliminary results suggest that body size (and occluded-ear EEA; a function of body size) could be a potential, underlying driver of NIHL susceptibility differences, rather than true sex differences.