Occupational hearing loss--an otologist's view of a long-term study

Tinnitus prevalence in industrial hearing loss compensation claimants

In a study of 3466 claimants for noise-induced occupational hearing loss tinnitus was reported by half of the patients. Its characteristics in this select group were different from tinnitus seen in other groups. Specifically, tinnitus prevalence seemed to be independent of age, state of hearing and duration of noise exposure if greater than 10 years. The reasons for these differences are unclear, though the possibility of financial motivation by some claimants is raised. Further work in this area is urgently required to achieve standardization and objectivity. Being a subjective complaint these aims will be difficult to accomplish. However not until then can a fair handicap scale be developed for workers who develop this disquieting symptom as a result of their occupation.

Development of hearing loss during long-term exposure to occupational noise. A 20-year follow-up study

Occupational noise-induced hearing loss is still responsible for the majority of occupational ailments and injuries, with very large sums being paid in compensation. Repeated hearing tests over a 20-year period have been performed on 319 employees of a timber processing firm, working in sawmills and paper pulp production, exposed to mean noise levels of around 95-100 dB (A) and in a chemicals division with mean noise exposure levels of 80-90 dB (A). During the observation period, mean hearing levels deteriorated slowly, especially at 4 kHz, but no dramatic changes from one year to another were seen. We therefore propose 3-year intervals between regular hearing tests in this type of industry where noise exposure is predominantly of the continuous type, thus releasing resources for more active measures against noise-induced hearing loss. Cases of manifest hearing loss or otherwise at risk must of course be followed up at shorter intervals. A remarkably large proportion of the employees in the chemicals division suffered a hearing loss corresponding to 10% disablement according to Swedish criteria, which raises the question of a possible relation between exposure to industrial solvents and hearing loss.

Results of otologic referrals in an industrial hearing conservation program

Baseline and periodic audiometry was performed on noise-exposed workers in 21 industrial plants. Workers showing moderate hearing loss, asymmetry, or significant threshold shifts were referred for otologic evaluation. The overall referral rate was 2.76%. Of 107 referrals, 53% had otologic diagnoses other than noise-induced hearing loss, or required specific intervention, or both. The results support the use of criteria at least as stringent as those used in this study.

Speech pure tone audiometry as a screen for exaggerated hearing loss in industrial claims

We examined 596 patients referred with possible noise-induced hearing loss, by conventional and cortical evoked response audiometry. Discrepancies between the two tests identified 121 (20.3%) as exaggerating their hearing loss. We then studied the validity of simple conventional tests, which would be available in primary diagnostic facilities, in screening for the exaggrerators we had idenfied. By selecting those whose puretone average (for 0.5 and 1 kHz) was more than 10 dB different from the speech reception threshold, or whose initial puretone threshold at 0.5 kHz was 40 dB or greater, we identified 112 (93%) of the exaggerators, at the cost of additional examination of 209 (35% of the total) false-positive. However, this screening means that 46% of the claimants could be evaluated completely in a primary diagnostic facility, and only a small fraction of the exaggerator should be overlook.