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Hearing Loss and Serum Lipid Profile Differences among Healthcare Versus Automotive Industry Workers: Cross-Sectional
Ramin Mehrdad1, Mahsa Naserpour2, Gholamreza Pouryaghoub1
1Center for Research on Occupational Diseases, Tehran University of Medical Sciences, Tehran, Iran.
Background:
Noise-induced hearing loss remains a common occupational disease. Although hazardous noise is primary cause, metabolic factors like dyslipidaemia may contribute, yet comparative evidence across diverse occupational settings remains limited.
Objective:
This study aimed to compare hearing thresholds and serum lipid profiles between healthcare employees and automotive industry workers and to assess the relative contributions of occupational noise exposure and dyslipidaemia to auditory outcomes.
Methods:
In this cross-sectional study, 9965 employees (5698 automotive workers and 4267 healthcare employees) were evaluated. Pure-tone audiometry was performed in accordance with International Organization for Standardization 8253-1 standards, and fasting lipid panels were analysed using standardised protocols. Occupational noise exposure was characterised using representative workplace monitoring data. Healthcare staff experienced the equivalent continuous sound level (LAeq) 60-70 dBA, exceeding WHO comfort recommendations. Automotive workers were exposed to LAeq 75-85 dBA, above long-term exposure limits. Comparative analyses were conducted using independent-samples t-tests and chi-square tests. Multivariable regression models were applied to identify independent predictors of hearing thresholds.
Results:
Despite their higher noise exposure, automotive workers demonstrated significantly better auditory thresholds than healthcare employees (mean binaural threshold: 8.2 ± 6.8 dB vs. 10.7 ± 8.0 dB; P < 0.001). Occupation type was an independent predictor of hearing status. Lipid parameters (total cholesterol, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, non-HDL cholesterol and triglycerides) showed only weak and clinically negligible associations with auditory thresholds.
Conclusions:
Hearing outcomes were more strongly influenced by occupational setting and preventive frameworks than by noise intensity or lipid status. Structured hearing conservation programs in the automotive sector showed protective effects, contrasting with limited measures in healthcare workplaces. These findings highlight the need to extend hearing conservation strategies beyond other sectors.
