The influence of a noisy environment on hearing impairment and tinnitus: The hearing outcomes of 50-year-old male Japan ground self-defense force personnel.

Objectives: Hearing loss is one of the biggest health problems in the world and occupational noise-induced hearing loss is recognized as the most common work-related illness. However, many factors that result in hearing loss make it difficult to define the specific factor that induces noise-induced hearing loss. To access the exact effect of occupational noise exposure on hearing, we conducted a cross-sectional cohort study of the relationship between noise exposure and hearing impairment in 50-year-old male Japanese Self-Defense Force (JSDF) personnel who work in a noisy environment. This population is ideal for the detection of noise-induced hearing impairments due to the homogeneity of genetic and social backgrounds.

Methods: The data utilized in this study were collected from a "50-year-old milestone health examination" of the JSDF from July 2013 to October 2015. One thousand sixty-seven male personnel were enrolled in the study. Pure-tone audiometry was conducted with an audiometer. A survey questionnaire asked participants to self-report occupational noise exposure.

Results: This cohort revealed that noise-exposed personnel had a higher hearing threshold and a higher odds ratio in 1) the average threshold of 4 frequencies (500 + 1000 + 2000 + 4000 Hz / 4), 2) the average threshold of higher 3 frequencies (2000 + 4000 + 8000 Hz / 3), and 3) the threshold of 4 kHz compared to no noise-exposed control personnel. The prevalence of tinnitus was also significantly higher in the noise-exposed group.

Conclusions: This study provides specific evidence for the relationship between noise exposure and noise-induced hearing impairments.