Prevalence of occupational noise-induced hearing loss and its associated factors among marine technicians working on the Royal Malaysian Navy vessels

INTRODUCTION: Noise-induced hearing loss (NIHL) is the second most common form of sensorineural hearing loss. It is one of the occupational health concerns worldwide with a prevalence rate of 16%. In Malaysia, there is an increasing trend of occupational NIHL prevalence encompassing agriculture, manufacturing, transportation, and construction sectors. The Malaysian Armed Forces (MAF) personnel, particularly the marine technicians of the Royal Malaysian Navy (RMN), have a heightened risk of developing NIHL due to prolonged exposure to hazardous noise levels onboard the military vessels. Previous studies involving MAF participants recorded a prevalence rate of approximately 22%. However, limited information is available regarding occupational NIHL among the RMN marine technicians. This study aimed to determine the prevalence of occupational NIHL and its associated factors among marine technicians working on the RMN vessels.

MATERIALS AND METHODS: A cross-sectional study was conducted among 127 randomly selected participants among marine technicians working on RMN vessels stationed at the Lumut Naval Base, Perak, Malaysia. The research instruments were questionnaires that contained information about sociodemographic, socioeconomic, occupational characteristics, and lifestyle behaviours, followed by a pure tone audiometric (PTA) assessment. Diagnosis of NIHL was made when the hearing threshold was ≥25 dB at 3 kHz to 6 kHz, with a recovery at 8 kHz on PTA.

RESULTS: The participants' median age was 32 years (interquartile range=27-37 years). The prevalence of occupational NIHL was 29.9% (95% CI=22.1-38.7). Factors associated with occupational NIHL on unadjusted regression analysis include age >30 years (OR=2.56, p=0.0185), middle household income (OR=2.76, p=0.0227), military rank especially the warrant officer (OR=7.12, p=0.0038), and length of service ≥15 years (OR=2.40, p=0.0246). After adjusting for ethnicity, smoking status, types of vessels, and participation in noise-related leisure activities, middle household income (OR=3.15, 95% CI=1.29- 7.87, p=0.0121) and warrant officer (OR=4.38, 95% CI=1.08- 20.52, p=0.0384) remained as significant predictors for occupational NIHL in this population.

CONCLUSION: In this study, the marine technicians working on board the RMN vessels had a higher prevalence of occupational NIHL compared to the prevalence among other MAF personnel as well as the global data. In addition, the probabilities of having occupational NIHL were significantly higher for middle-income technicians and those who ranked as warrant officers. These findings highlight the need for routine audiometric assessment and adoption of hearing conservation initiatives for individuals at high risk within this occupational cohort.