Association of occupational noise exposure and shift work with non-alcoholic fatty liver disease: a cross-sectional study of male workers in the Chinese automobile manufacturing industry

Objective This study aimed to determine the relationship between occupational noise, shift work and non-alcoholic fatty liver disease (NAFLD) in male workers in the automobile manufacturing industry. Design Cross-sectional study. Setting This study was carried out at the Guangzhou Twelfth People's Hospital using data from April to September 2022. Participants A total of 4672 eligible participants were included in the study. Primary and secondary outcome measures Diagnosis of NAFLD was made using ultrasound. Noise was detected according to the Measurement of Physical Factors in the Workplace-Part 8: Noise. Environmental noise intensity was assessed using an EDGE personal noise dosimeter manufactured by CASELLA (UK). The working status of workers was investigated by questionnaire. Results The OR of NAFLD was 1.39 (1.03, 1.88) in the cumulative noise exposure (CNE)>= 95 group compared with CNE<85 group. Improved risk of NAFLD in workers with shift work compared with those without shift work (OR=1.35, 95% CI: 1.09, 1.68). As stratified analyses showed, the ORs of NAFLD prevalence related to occupational noise and shift work exposure appear to be increased in young workers. When both shift work and noise exposure work are present simultaneously, the synergy index between them was 0.47 (95% CI: 0.25, 0.89). Combined effects analysis revealed that the OR of NAFLD was 2.02 (95% CI: 1.34, 2.99) in CNE >= 95 and cumulative length of night shifts work>2920 hours. Conclusion Occupational noise exposure may be an independent risk factor for NAFLD. It may synergistically affect disease when combined with night shift work, particularly among younger workers. These findings underscore the importance for companies to prioritise the management and training of younger workers, along with targeted occupational health education initiatives, as crucial measures for reducing the incidence of NAFLD.