In developing countries, like Namibia, there is limited data pertaining to the number of
individuals with hearing loss and its associated factors. This study aimed to determine the
prevalence of potential hearing loss in Namibian Class A mines and to describe the extrinsic
and intrinsic factors associated with hearing loss.
A cross-sectional design was utilised and data were collected from 132 respondents (mining
employees) from five different Class A mines throughout the country. A questionnaire and a
retrospective review of respondents’ medical records were utilised to determine the risk factors.
The most recent audiogram found in the respondents’ records was used to determine the
presence of potential hearing loss. Three definitions of potential hearing loss were used in this
study and included all major frequency hearing loss (AFHL), high frequency hearing loss
(HFHL) and low frequency hearing loss (LFHL). Potential hearing loss was identified when
the pure tone average (PTA) of 0.5, 1, 2, & 4kHz, 0.5, 1 & 2kHz and 4 & 8kHz respectively
was greater than 25dBHL in either one or both ears. Chi-square measurements or, where
necessary, Fisher’s exact tests, as well as Odds Ratios were used for the analysis of data. In
general a significance level of 5% was applied for all analyses.
Results indicated the prevalence of potential hearing loss in Namibian mining employees to be
27% and that both extrinsic and intrinsic factors were associated with hearing loss. The
extrinsic factors significantly associated with potential hearing loss were both occupational and
medical. The occupational factors found to be significant were the number of years employed
in whole life >10 years (p=0.012; OR=3.1, 95% CI=1.3-7.9), the number of years employed in
current job > 10 years (p=0.01; OR=3.9, 95% CI1.7-8.8) and the non-availability of formal
training in prevention of hearing loss (p=0.022; OR=0.3, 95% CI (0.1-0.9). Diabetes was the
sole significant extrinsic medical factor (p=0.035, OR=5, 95% CI 1.1-22.1). The only intrinsic
factor which was found to be significantly associated with hearing loss was Age, specifically
being older than 40 years (p=0.002; OR=3.5, 95% CI 1.6-7.8) and 50 years (p=0.001, OR=5.5,
95% CI1.9-15.8). A multiple logistic regression model of all significant factors found that only
no formal training of prevention of hearing loss was found to be significant in the presence of
all other factors (p=0.036, OR=0.036, 95% 0.1-0.92).
Findings from this study suggest that multiple factors may be associated with potential hearing
loss and not just the exposure to hazardous occupational conditions. Recommendations for
Stellenbosch University https://scholar.sun.ac.za
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future research and clinical practice should, therefore, include thorough investigations into the
aetiology of hearing loss. As this study focused on Class A mines, it is recommended that future
research be conducted in other mines that are not categorised as Class A mines.