Body mass index modifies the association between occupational noise exposure duration and ultrasound‑detected hepatic steatosis: A cross-sectional study among male factory workers

BACKGROUND: Metabolic dysfunction‑associated steatotic liver disease (MASLD) is a multisystem metabolic disorder. The impact of occupational noise exposure on metabolic processes through non-auditory pathways is also closely associated with hepatic steatosis in addition to obesity. Most studies examine noise exposure or Body Mass Index (BMI) alone on ultrasound-detected hepatic steatosis(UDHS), while few examine BMI's interaction with occupational noise duration. The underlying mechanisms of these combined effects remain unclear. The correlation between occupational noise exposure duration and UDHS in automotive manufacturing workers is examined, as well as the interactive role of BMI. OBJECTIVE: This study investigates the correlation between occupational noise exposure duration and UDHS in automotive manufacturing workers, as well as the interactive moderating effect of BMI on this association. METHODS: A retrospective study involved 769 male workers exposed to occupational noise. Ultrasound was used to diagnose hepatic steatosis. Modified Poisson regression with robust variance estimation was used to analyze variable associations. A slope analysis and Johnson-Neyman test were used to validate BMI and variable interactions. A sensitivity analysis was performed to ensure robustness. RESULTS: Overall, 53.2% of workers had UDHS. Noise exposure duration showed a significant independent association with UDHS,with a negative interaction effect on BMI (P = 0.006) after adjusting for confounding factors. In normal-weight workers, each additional year of noise exposure was associated with an 8.2% higher UDHS likelihood (P < 0.001), but not statistically significant in overweight/obese individuals; BMI = 27.7 kg/m² represented the critical threshold where the magnitude of this association approached zero. Alcohol consumption and overweight/obesity were independent risk factors. CONCLUSION: Noise exposure is associated with UDHS risk among male workers, yet BMI modifies this association, whereby the magnitude of this association weakens as BMI increases. These findings are specific to male factory workers and cannot be generalized to female populations. Accordingly, tailored occupational health protection strategies can be developed for noise-exposed populations.