Hearing loss in divers: a 6-year prospective study.

Occupational diving is associated with hearing loss, but the cause is disputed. Our aim was to follow a cohort of divers through the first 6 years of their career in order to look for evidence of permanent threshold shift associated with diving activity, occupational noise exposure or acute injuries. Hearing was measured by pure tone audiometry in 67 participants at a basic course for working divers. Hearing thresholds were adjusted for age (ISO 7029). The subjects were examined and interviewed by an otologist. Additional medical and exposure data were recorded in questionnaires and personal logbooks. The procedure was repeated after 3 and 6 years. None of the subjects suffered inner ear barotrauma or inner ear decompression sickness during follow-up. Middle ear barotrauma was common. The prevalence of subjective hearing difficulties increased during follow-up, and there was a significant threshold shift at 4 kHz (mean 2.6 dB, 95% confidence interval 0.9-4.3 dB). Both subjective and objective hearing loss was associated with occupational noise exposure, but not with diving frequency or with a history of middle ear barotrauma. In the absence of manifest inner ear barotrauma or inner ear decompression sickness, noise seems to be the most important cause of long-term hearing loss in occupational divers. This study did not find evidence of long-term hearing loss caused by uneventful diving per se.