Tinnitus as an early indicator of permanent hearing loss. A 15 year longitudinal study of noise exposed workers.

A retrospective study was designed to evaluate tinnitus (ringing or other sounds in the ears or head) as a potential early indicator of permanent hearing loss in a population of noise exposed workers. Data were examined from 91 male employees working in environments with noise levels ranging from 8 hour time weighted averages of 85 to 101 dBA over a period of 15 years. Results of annual audiometric testing were obtained as part of an ongoing hearing conservation program conducted since 1971 by ESCO Corporation, a steel foundry located in the Portland, Oregon metropolitan area. Results indicate the prevalence of tinnitus increases more than two and one half times for workers experiencing maximum threshold shifts > or = 15 decibels in hearing level (dBHL). Results also provide evidence that reports of tinnitus at the time of annual audiometric testing may be useful in identifying workers at greater risk for developing significant shifts in hearing thresholds.