Background: Leisure noise may have a significant impact on hearing thresholds and young adults are often exposed to loud music during leisure activities. This behavior puts them at risk of developing noise-induced hearing loss (NIHL). A frequent initial indication of NIHL is reduced hearing acuity at 4 kHz. The objective of the current study was to assess the role of the medial olivocochlear reflex (MOCR) in leisure noise-exposed individuals with and without a 4-kHz notch.
Materials and methods: Audiological evaluation, including pure-tone and immittance audiometry, was performed for 156 college-going, young adults between May 2019 to December 2019. All participants had averaged pure-tone audiometric thresholds within normal limits, bilaterally. Annual individual exposure to personal listening devices (PLDs) was calculated using the Noise Exposure Questionnaire. The participants were then categorized into exposed (with and without audiometric 4 kHz notch) and nonexposed groups. Transient-evoked otoacoustic emission amplitude and its contralateral suppression were measured using linear and nonlinear click stimuli to study the effect of leisure noise exposure on MOCR.
Results: A significantly reduced overall contralateral suppression effect in participants exposed to PLD usage (P = 0.01) in both linear and nonlinear modes. On the contrary, significantly increased suppression was observed in linear mode for the 4 kHz frequency band in the PLD-exposed group without an audiometric notch (P = 0.009), possibly suggesting an early biomarker of NIHL.
Conclusion: Measuring contralateral suppression of otoacoustic emissions may be an effective tool to detect early NIHL in leisure noise-exposed individuals.
Keywords: Medial olivocochlear reflex (MOCR); Noise Exposure Questionnaire (NEQ); noise-induced hearing loss (NIHL); transient-evoked otoacoustic emission (TEOAE).