Prevention of noise-induced hearing loss.

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.