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.
