Hearing thresholds among young professional divers: a 6-year longitudinal study.

INTRODUCTION: Diving is associated with pressure effects and noise exposure that can impair hearing. We were interested in finding out whether changes in hearing thresholds were related to cumulative exposure in young professional divers.

METHODS: In a prospective follow-up design, we studied a cohort of 47 men from the beginning of their education as professional divers at a mean age of 25.6 yr (range 18-38 yr). They had audiograms taken at baseline, after 1 and 3 yr, and finally after 6 yr, during which they performed 40-1458 (median 184) sea dives, most of them to a depth of 10 m or less. The hearing tests measured pure tone air conduction thresholds at 0.25-8.0 kHz in a sound-treated booth. Annual change of hearing thresholds were calculated by fitting linear regression lines to individual data. For purposes of analysis, the divers were divided into two groups, low-exposure (199 or fewer dives, n = 26) and high-exposure (200 or more dives, n = 21).

RESULTS: Hearing was better in the divers than in the general population at baseline and follow-up. At 6 yr, significant reductions were found in the divers' hearing at 4 kHz and 8 kHz. Significant increases in thresholds were found at 0.5, 2, 3, and 6 kHz for the right ear and 3, 4, and 6 kHz for the left ear. The annual change at 4 kHz was 0.95 dB in the left ear and 0.18 dB in the right ear (p = 0.01). There was no significant difference in hearing changes between the high- and low-exposure groups.

DISCUSSION: The results suggest that a mild hearing impairment can occur in young professional divers due to occupational and other noise exposure.