The Effect of Working Noise Exposure and Military Background on the Hearing Threshold / 예방의학회지

ABSTRACT

OBJECTIVES: Impaired hearing is a prevalent occupational hazard, not only in industry, but also in the armed forces. In military life, noise has unusual characteristics, and constitutes a serious hazard to hearing. The aim of this study was to analyze the hearing threshold data in order to compare the hearing loss among shipyard workers, representing different workers, and a military service background. METHODS: A cross-sectional audiological survey, combined with a questionnaire study, was conducted on a stratified random sample of 440 shipyard workers, with long-term exposure to noise. The employees were divided into four groups, according to their working and military service backgrounds, in relation to their exposure to noise. RESULTS: As expected, the working and military noise exposure group (Group I) had significantly poorer hearing than the other groups. The high frequencies (2-8 kHz) showed the greatest difference in terms of poorer hearing in both ears. The prevalence of noise-induced hearing loss (NIHL) was highest in Group I. A logistic regression analysis was applied to determine the dependence of the NIHL in relation to age, smoking, drinking, working duration, ear protection, past history of ear diseases, and working and military service backgrounds, on the noise exposure. The important factors found to be related to the NIHL, in relation to noise exposure were age, work duration, and working and military service backgrounds. The adjusted odds ratio estimates for NIHL in the right ear were 4.5 times greater (95% CI 1.7-11.6) for the military noise exposed group, and 7.9 times greater (95% CI 2.0-31.3) for the working noise exposed group than in the controls. The hearing thresholds at the pure-tone average and 4 kHz were significantly increased with age and work duration with both the working and military service backgrounds. CONCLUSIONS: From these results, specific preventive programs were planned, which should be assessed by epidemiological surveillance of the military noise exposed population.