Occupational noise and age: A longitudinal study of hearing sensitivity as a function of noise exposure and age in South African gold mine workers.
Leoni M Grobler, De Wet Swanepoel, Susan Strauss and 2 others
PMID 32242440WHAT IT FOUND
South African gold mine workers with high noise exposure had worse hearing at first test and lost more over repeated annual tests than administrative workers, even after accounting for age.
Age also contributed, especially at higher frequencies.
Key findings
01Noise-exposed rock drillers had worse baseline hearing and larger high-frequency threshold increases than non-exposed administration workers.
02Age contributed to threshold increases, because models without age adjustment showed larger year-to-year increases than models adjusted for age.
03Continued hearing threshold increases in the noise-exposed group occurred even in a setting where noise exposure was supposed to be controlled.
STILL TO COME
How it was doneWhat they foundWhat it means for SLPs
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What it does not show
This was an observational record review, so it shows that noise exposure and age were linked to hearing decline, not that either one alone caused it. The analysed sample was restricted to workers with complete repeated audiograms, so workers without those records were excluded. The noise-exposed group already had worse hearing at the first audiogram, so some damage occurred before the study period. Genetic predisposition, health co-morbidities, ototoxicity, non-occupational noise and chemical exposure were not measured. The sample was mostly black male gold mine workers, so it may not apply to other populations.
The easy way to misread this
Do not read this as proof that removing noise exposure after years of exposure reverses or stops hearing loss. The noise-exposed group started with worse hearing and continued to decline, and the authors say this may reflect incomplete control of exposure or lasting effects of earlier exposure.