Abstract
Background: Lesotho Flying Doctor Service workers use aircraft as a main mode of transport to deliver health services in to hard-to-reach remote areas of Lesotho. This mode of transport presents a major source of occupational noise pollution at their workplace. Consecutively depending on the level of exposure to noise, employees are at risk of suffering from occupational diseases such as hypertension and noise-induced hearing loss with other complications these diseases could bring along.
Aim: The study aimed to ascertain the association between occupational noise exposure and hypertension. Secondly, the association between occupational noise exposure and hearing impairment in Lesotho Flying Doctor Service Workers.
Objectives: To determine the proportion of LFDS employees affected by hypertension and hearing impairment following noise exposure; to determine which group of workers is mostly affected by the disease; and lastly to assess the relationship between noise exposure and these two diseases namely hypertension and hearing loss.
Methodology: A quantitative study design was applied, it consisted of a retrospective cohort component that provided information about past exposure and a prospective component that assessed the current health status of the research participants through direct audiometry and blood pressure measurements. A stratified random sampling was used to select 350 employees from the eleven health centers of the Lesotho Flying Doctor Service Department, of which 88 participants were exposed, while 262 participants were unexposed to noise. Data collected from this research were analyzed using the Statistical Package for Social Sciences Software IBM-SPSS version 29.0 and data analysis was performed by running frequencies and descriptive statistics. To compute the central tendency and dispersion of data, frequency distribution tables, means, and standard deviations were used; Logistic regression such as ANOVA, T-test, and correlation tests were used to assess the association and relationship between noise exposure, hypertension, hearing loss, gender, age, and type of ear.
Results: Respondents female-to-male sex ratio was 1.8, with a mean of 1.65 and a standard deviation of .079. Out of the whole sample(n=350), 97 (28%) had hypertension. Of 88 exposed
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participants only 22 (25%) had hypertension. And out of 262 unexposed participants, 75 (28.6%) had hypertension. Of 350 participants, 113 (32.3%) had hearing loss for the overall sample. Out of 88 exposed respondents, 64 (72%) had hearing loss, against only 18.7% of hearing loss in unexposed study subjects or 49 over 262 respondents. ANOVA for the correlation between age and hypertension revealed a significant mean difference in Systolic BP mmHg (F (66.220) = 24.15,p < .001). Results also showed the correlation between hypertension and job entry date, the mean difference between the two variables was 339, and 8 respectively for normal, abnormally low, and abnormally high BP, the difference was statistically significant with a lower bound of the true significance between (.000 - .200). The risk of presenting severe hearing loss in hypertensive participants was significant for both systolic BP (r = .191) and diastolic BP (r = .146), the correlation was positive and statistically significant p < .01. From otoscopy, 23% of participants had hearing loss, while with audiometry 32.6% of participants had hearing problems, and the majority suffered from the left ear.
Conclusion: Hypertension was found not to be directed and correlated to noise exposure, besides noise, other factors could have contributed to its occurrence. However, respondents diagnosed with hypertension were at high risk for presenting severe hearing loss. Age and duration of employment positively contributed to disease occurrence, while gender did not affect the outcomes and informed that males and females could be affected equally. Hearing impairment was found to be significantly correlated to noise exposure. Lastly, an audiometric test was able to detect hearing problems in some participants before even they presented abnormalities on otoscopy, therefore audiometry proved to be the best screening test for prevention and control.
Keywords: Noise exposure; Noise-induced hearing loss; hypertension; Lesotho Flying Doctor Service employees; degree of hearing