Original Research - Special Collection: Occupational Hearing Loss in Africa

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, Piet Becker, Zahan Eloff
South African Journal of Communication Disorders | Vol 67, No 2 | a687 | DOI: https://doi.org/10.4102/sajcd.v67i2.687 | © 2020 Leoni M. Grobler, De Wet Swanepoel, Susan Strauss, Piet Becker, Zahan Eloff | This work is licensed under CC Attribution 4.0
Submitted: 23 October 2019 | Published: 17 March 2020

About the author(s)

Leoni M. Grobler, Department of Speech-Language Pathology and Audiology, Faculty of Humanities, University of Pretoria, Pretoria, South Africa
De Wet Swanepoel, Department of Speech-Language Therapy and Audiology, Faculty of Humanities, University of Pretoria, Pretoria, South Africa
Susan Strauss, Department of Speech-Language Therapy and Audiology, Faculty of Humanities, University of Pretoria, Pretoria, South Africa
Piet Becker, Department of Health Sciences, Faculty of Health, University of Pretoria, Pretoria, South Africa
Zahan Eloff, Occupational Health Department, AngloGold Ashanti, Carletonville, South Africa


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Abstract

Background: A relationship exists between occupational noise exposure and age, which remains poorly understood.

Objectives: The aim of this study was to establish the relationship between hearing loss and age over time.

Method: Audiological data from 2583 mine workers in South Africa were utilised. Data were received from a non-noise exposed group (NNEG) (n = 951) and a noise exposed group (NEG) (≥85 dBA) (n = 1632). Data comprised a low-frequency average (LFA512) (average of audiological thresholds for 0.5 kHz, 1 kHz and 2 kHz) and high-frequency average (HFA346) (average of audiological thresholds for 3 kHz, 4 kHz and 6 kHz). Data were compared by using mixed-effects regression analysis.

Results: Base threshold values were higher for the NEG than for the NNEG across frequencies. All year-to-year increases in mean hearing thresholds were statistically significant (p < 0.01). When correcting for age, increases in mean hearing thresholds were higher for the NEG than for the NNEG for HFA346 (3.5 dB vs. 2.9 dB decline over a 4-year period) but similar for LFA512 (0.6 dB vs. 0.7 dB decline). Uncorrected for age, increases in mean hearing thresholds were higher than when age was corrected for.

Conclusion: Age and occupational noise exposure influence hearing thresholds over time. The continued increase in hearing thresholds of the NEG above that of the NNEG can be related to ineffective noise management programmes and/or the fact that early noise exposure leads to a higher burden of hearing loss over time – even after noise exposure had stopped.


Keywords

Age-related hearing loss; Noise exposure; Noise-induced hearing loss; Occupational noise exposure; Mining

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