A Cross-Sectional Study of the Time of Onset of Hearing Loss in Bus Drivers Following Exposure to Occupational Noise.

Abstract

Background and objectives: Occupational noise exposure is a significant risk factor for hearing loss, affecting approximately 5% of the global population. Although noise-induced hearing loss is commonly associated with reduced sensitivity to pure tones, there is limited information regarding when this hearing loss begins after noise exposure. This study aimed to investigate the time of onset of hearing loss in bus drivers exposed to noise for varying durations.

Subjects and methods: The study involved 102 bus drivers aged 25-40 years who had been exposed to noise for periods ranging from 6 months to over 10 years. A control group comprising 102 age-matched individuals without noise exposure was also included. Pure-tone audiometry was performed to assess hearing loss, and time of onset of hearing loss relative to noise exposure duration was evaluated.

Results: Bus drivers experienced only "slight" hearing loss, even after 10 years of noise exposure. By contrast, reduced sensitivity to pure tones was observed after 25 to 48 months of exposure.

Conclusions: This study confirms that prolonged noise exposure leads to "slight" hearing loss, which can appear as early as 25-48 months after exposure to noise. Among individuals under 40 years of age, significant hearing loss appeared to occur only after 10 or more years of exposure. These findings suggest that the impact of noise on hearing acuity may have been overestimated in previous studies.