PubMed · 8107729
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B S Levy, D H Wegman. 1994-03-10. Hearing loss.. https://pubmed.ncbi.nlm.nih.gov/8107729/
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Histological and functional derangement of the vestibular system has been reported in laboratory animals exposed to high levels of noise. However, reports of clinical series give contradictory results with regard to vestibular disturbances in industrial workers and military personnel suffering from noise-induced hearing loss (NIHL). This study evaluates vestibular function in 22 men with documented NIHL and in 21 matched controls, using electro-nystagmography (ENG) and the smooth harmonic acceleration (SHA) test. There was a significantly lower vestibulo-ocular reflex gain (p = 0.05), and a tendency towards decreased caloric response in the patients. There were no differences between patient and control groups in: incidence of vertigo and of spontaneous, positional and positioning nystagmus; directional preponderance and canal paresis in the ENG; or in phase and asymmetry parameters in the SHA test. These results demonstrated a symmetrical, centrally compensated decrease in vestibular end-organ response associated with symmetrical hearing loss in the patients. Statistically significant correlations were found between average hearing loss, and decrease in average vestibulo-ocular reflex gain (p = 0.01) and ENG caloric lateralization (p = 0.02). These correlations might indicate a single mechanism for both cochlear and vestibular NIHL. The results imply subclinical, well compensated malfunction of the vestibular system associated with NIHL.
OBJECTIVES: To review the evidence suggesting that occupational hearing conservation programs prevent noise-induced hearing loss; to describe the features, prevalence, and handicap associated with noise-induced hearing loss; and to describe the otolaryngologist's role in prevention of noise-induced hearing loss. DATA SOURCES: Recent statements from the American College of Occupational Medicine, the National Institutes of Health, and the International Organization for Standardization are supplemented by published articles known to the author (no formal literature search was done). STUDY SELECTION: Articles that purported to measure the effects of occupational hearing conservation programs on preventing noise-induced hearing loss. DATA EXTRACTION: Each article was separately critiqued without a priori assessment criteria. DATA SYNTHESIS: Several studies suggest that occupational hearing conservation programs prevent noise-induced hearing loss, but none of these are conclusive. No randomized clinical trial has been reported, of which I am aware, and previously reported data suffer from one or more of the following shortcomings: failure to match treatment and control groups for age, nonoccupational noise exposure, and/or prior hearing loss; failure to control for audiometric learning effects; and inclusion of workers who had already worked long careers without hearing protection (and thus had little risk of additional noise-induced loss). CONCLUSION: Although noise reduction for individuals obviously can prevent noise-induced hearing loss, to my knowledge, no single study offers convincing evidence of the efficacy of occupational hearing conservation programs, primarily due to methodologic flaws.
Loss of hearing due to chronic noise exposition is a well-known pathology and many nations have regulations for the protection of workers with periodical audiometry and ONT check-ups. For the last 15 years, the authors have followed state railway workers of the Milan area who were professionally exposed to noise. All were periodically examined by ONT specialists and submitted to audiometry. The findings underscore the importance of these periodical examinations and their efficacy for the prevention of hearing loss due to noise.