Hearing symptoms and audiometry in professional divers and offshore workers

AIMS: The aims are to compare hearing loss between professional divers and offshore workers and to study whether hearing loss symptoms reflected physical disorder. A secondary objective was to study total threshold shift assessment as a method of detecting noise-induced hearing loss (NIHL). METHODS: Participants (151 divers and 120 offshore workers) completed a questionnaire for symptoms and screening audiometry. Audiograms were assessed for total threshold shift at 1, 2, 3, 4 and 6 kHz and the prevalence of referral (within population 5th centile) or warning levels (within population 20th centile) of hearing loss. Audiograms were assessed for an NIHL pattern at four levels by two occupational physicians. RESULTS: Hearing loss symptoms were commoner in divers at all levels of hearing loss regardless of differences between groups on audiometry. Hearing loss in offshore workers was within the population age-adjusted norm. Thirteen per cent of divers were within the 5th percentile for threshold shift for the population norm in contrast to 4% of offshore workers and this was predominantly left sided (OR 3.16, 95% CI 1.13-8.93). This difference was lost after adjustment for history of regular exposure to explosion or gunfire. Divers were more likely to have a pattern of severe NIHL on the left (OR 4.61, 95% CI 1.39-15.39, P < 0.05). Approximately 50% of participants with severe NIHL did not have a referral level of hearing loss. CONCLUSIONS: Divers suffer more NIHL than a control population. Current guidance on the assessment of total threshold shift for the detection of significant NIHL was inadequate in the sample studied.