Hearing damage in military service. A study on 38,294 conscripts

In an audiometric study on 38,294 conscripts, noise-induced high-frequency hearing deterioration during basic training (mean 245 days) was studied. On reporting for training, 29% were found to have hearing defects, predominantly in the high-frequency area. After training, high-frequency deterioration, predominantly unilateral or asymmetrical, was found in 5%. In 0.5%, this deterioration had reached a symptomatic level, causing minor handicap. In 0.03% (12 conscripts), it fulfilled the criterion of "10% hearing disability" applied in Swedish industrial insurance. The incidence of high-frequency deterioration rose from 3% in conscripts having 'normal' hearing on reporting, to 17% among those with the greatest hearing loss on reporting. This means that the presence of sensorineural hearing loss implies an increased risk of noise-induced hearing deterioration. No correlation was found between hearing status on reporting and magnitude of deterioration during training. The results imply that hearing data obtained on reporting for training should be taken into account in deciding the assignability of conscripts to noisy training courses and posts.