Mediating role of metabolic dysfunction-associated fatty liver disease in the association between individual-level noise exposure and liver enzymes in Chinese automotive manufacturing workers

Limited research has explored the relationship between occupational noise exposure and liver enzymes, particularly at the individual exposure level. This study examines the association between occupational noise exposure and liver enzyme levels and the mediating role of metabolic dysfunction-associated fatty liver disease (MAFLD). We recruited 3,427 workers from two factories in Guangzhou, China. Cumulative noise exposure (CNE) was estimated based on noise levels and years of exposure. Alanine aminotransferase (ALT), aspartate aminotransferase (AST), and γ-glutamyl transferase (GGT) levels were obtained from medical examinations. Linear and logistic regression models, along with subgroup and mediation analyses, were employed to assess the associations between CNE and liver enzyme levels. Cumulative noise exposure (CNE) demonstrated a dose-response relationship with liver health indicators, with significant associations observed across different statistical models. Specifically, each 10 dB(A)-year increase in CNE was associated with a 2.10 U/L increase in ALT levels and a 26% higher risk of elevated ALT. Concurrently, categorical models revealed that workers in the highest CNE group had significantly increased risks of elevated ALT, AST, and GGT, with the most pronounced effect observed for AST. These associations were significantly strengthened by insufficient physical activity ( P for interaction