Evaluation of hidden hearing loss in normal-hearing firearm users

Abstract

Some noise exposures resulting in temporary threshold shift (TTS) result in cochlear synaptopathy. The purpose of this retrospective study was to evaluate a human population that might be at risk for noise-induced cochlear synaptopathy (i.e., “hidden hearing loss”). Participants were firearm users who were (1) at-risk for prior audiometric noise-induced threshold shifts, given their history of firearm use, (2) likely to have experienced complete threshold recovery if any prior TTS had occurred, based on this study’s normal-hearing inclusion criteria, and (3) not at-risk for significant age-related synaptopathic loss, based on this study’s young-adult inclusion criteria. 70 participants (age 18–25 yr) were enrolled, including 33 firearm users experimental (EXP), and 37 non-firearm users control (CNTRL). All participants were required to exhibit audiometric thresholds ≤20 dB HL bilaterally, from 0.25 to 8 kHz. The study was designed to test the hypothesis that EXP participants would exhibit a reduced cochlear nerve response compared to CNTRL participants, despite normal-hearing sensitivity in both groups. No statistically significant group differences in auditory performance were detected between the CNTRL and EXP participants on standard audiom to etry, extended high-frequency audiometry, Words-in-Noise performance, distortion product otoacoustic emission, middle ear muscle reflex, or auditory brainstem response. Importantly, 91% of EXP participants reported that they wore hearing protection either “all the time” or “almost all the time” while using firearms. The data suggest that consistent use of hearing protection during firearm use can effectively protect cochlear and neural measures of auditory function, including suprathreshold responses. The current results do not exclude the possibility that neural pathology may be evident in firearm users with less consistent hearing protection use. However, firearm users with less consistent hearing protection use are also more likely to exhibit threshold elevation, among other cochlear deficits, thereby confounding the isolation of any potentially selective neural deficits. Taken together, it seems most likely that firearm users who consistently and correctly use hearing protection will exhibit preserved measures of cochlear and neural function, while firearm users who inconsistently and incorrectly use hearing protection are most likely to exhibit cochlear injury, rather than evidence of selective neural injury in the absence of cochlear injury.

Effects of Age and Noise Exposure History on Auditory Nerve Response Amplitudes: A Systematic Review, Study, and Meta-Analysis

“…Sex differences in self-reported noise exposure history and AN response amplitudes have been reported in other studies, with males more likely to report a positive noise exposure history and exhibit smaller AN response amplitudes than females (e.g., Dewey et al, 2020; Fulbright et al, 2017; Grinn & Le Prell, 2022; Johannesen et al, 2019). Previous studies of noise exposure history and AN function that have investigated and controlled for sex differences in the relationship between noise exposure and AN response amplitudes have failed to identify a significant relationship between noise exposure history and AN function in either males or females (Dewey et al, 2020; Fulbright et al, 2017; Grinn & Le Prell, 2022; Grinn et al, 2017; Washnik et al, 2023). We also did not find evidence for a difference in the relationship between noise exposure history and AN response amplitudes between male and female participants in our meta-analysis.…”

“…We used linear regression models (LM) to test whether CAP N1 amplitudes were predicted by age group (younger or older) and noise exposure history (positive or negative). Participant sex was incorporated into our statistical analyses to evaluate whether sex-differences in AN response amplitudes and noise exposure history could account for variability in CAP N1 amplitudes explained by age and noise exposure history (Dewey et al, 2020; Fulbright et al, 2017; Grinn & Le Prell, 2022; e.g., Johannesen et al, 2019). Average pure-tone thresholds from 0.5 to 4 kHz were similarly incorporated into our statistical analyses to evaluate whether inter-subject variability in pure-tone thresholds across frequencies could account for variability in CAP N1 amplitudes explained by age and noise exposure history.…”

“…There has been some evidence suggesting that not all types of noise exposure affect the AN equally. Impulse/impact noise, such as from firearms, has been found to be negatively associated with AN response amplitudes (e.g., Grinn & Le Prell, 2022; Pinsonnault-Skvarenina et al, 2022b). When our data were reanalyzed with noise exposure exclusively restricted to a history of exposure to firearms, the pattern of relationships reported above did not change.…”

Investigação dos efeitos da exposição ao ruído ocupacional nas vias auditivas periférica e central de indivíduos normo-ouvintes

“…Este resultado corrobora o estudo de Grinn e LePrell (2022), que avaliaram usuários de arma de fogo com um grupo controle sem exposição ao ruído, no qual também não foram observadas diferenças nos limiares da AAF entre os grupos.Por outro lado, outros estudos encontram diferenças na avaliação da AAF.…”

“…. Contudo, existem grandes variações nos resultados encontrados, que podem ser justificadas pelas diferentes metodologias adotadas e características da casuística dos estudos(Le Prell, Clavier e Bao, 2023).Por fim, também consideramos uma limitação relevante e abordado no estudo de Grinn e LePrell (2022), refere-se ao uso dos dispositivos de proteção auditiva (DPA), que têm o papel de minimizar os efeitos que a exposição ao ruído tem sobre o sistema auditivo, principalmente evitando a perda auditiva. No estudo citado, os pesquisadores relataram que os participantes, embora normo-ouvintes, que usavam de maneira inadequada ou não utilizaram o DPA, apresentavam resultados piores nas avaliações realizadas.…”