Objectives: Aging and noise are generally considered the most common causes of adult hearing loss in developed countries. This study estimates the contributions of aging and occupational noise in the United States.
Design: A model of hearing loss burden in American adults was constructed using data from the Census Bureau, from an international standard that predicts age-related and noise-induced hearing loss (ISO-1999), from the American Medical Association method of determining hearing impairment, and from sources estimating the distribution of occupational noise exposure in different age and sex groups.
Results: Occupational noise exposure probably accounts for less than 10% of the burden of adult hearing loss in the United States; most of the rest is age-related. Most of the occupational noise burden is attributable to unprotected exposures above 95 dBA, and becomes apparent in middle age, when occupational noise exposure has ceased but age-related threshold shifts are added to prior noise-induced shifts, resulting in clinically significant impairment.
Conclusions: In our current state of knowledge, noise-induced hearing loss is still the most important preventable cause of hearing loss in the United States. The burden of occupational noise-induced hearing loss could probably be reduced by stricter enforcement of existing regulations. Longer lifespans in developed countries and migration of manufacturing jobs to developing countries will continue to reduce the relative contribution of occupational hearing loss in countries like the United States. Preventive interventions for age-related hearing loss, even if only partially effective, could potentially reduce the burden of adult hearing loss more than elimination of occupational noise.