No accelerated 20‐year hearing decline after occupational noise exposure has ceased: The HUNT study

Abstract

AbstractObjectivesIt has been suggested that noise exposure can accelerate hearing decline after the noise exposure has ceased. We aimed to assess long‐term hearing decline in persons with and without prior occupational noise exposure.MethodsWe conducted a population‐based longitudinal study in Norway using the Trøndelag Health Study (HUNT) from 1996 to 1998 (baseline) and from 2017 to 2019 (follow‐up). The sample included 1648 participants with baseline age ≥55 years (42% men, mean age 60 years) and <5 years occupational noise exposure after baseline. We analyzed the association between occupational noise exposure before baseline and mean hearing decline between 1998 and 2018 (20‐year decline) at each frequency, adjusted for age, sex, education, and impulse noise exposure before baseline.ResultsOccupational noise exposure before baseline (N = 603) was associated with baseline hearing loss, but not with later accelerated 20‐year decline, at any frequency. Noise‐exposed persons had less subsequent 20‐year decline at 3 kHz than did nonexposed. Restricting the noise‐exposed group to persons who also had a baseline Coles notch (hearing thresholds at 3, 4, or 6 kHz of 10 dB or more compared with thresholds at 1 or 2 kHz and 6 or 8 kHz; N = 211), the exposed group showed less 20‐year decline at both 3 and 4 kHz, as well as less accelerated 20‐year decline at 8 kHz, compared with the nonexposed.ConclusionOur large long‐term longitudinal study shows no increased risk of continuing hearing decline after occupational noise exposure has ceased. The finding supports a conclusion that ear damage stops when the noise exposure is ended.