Hearing loss from industrial noise, head injury and ear disease. A multivariate analysis on audiometric examinations of 110,647 workers.

From compulsory screening examinations of 260,917 noise-exposed workers standardized audiograms as well as medical and occupational histories of 110,647 workers were selected because of full-time exposure to well-defined noise greater than 85 dB (A) and analyzed by loglinear and multiple linear regression. The most important factors for prediction of pure-tone hearing loss at 4 kHz were found to be age, sex and noise immission level. For predicting speech impairment and handicap the history of ear disease, head injury and tinnitus were more important than noise immission level. Dose-response relationships are given to improve prevention and compensation of hearing loss from combined factors.