Synergistic Effect of Ambient PM_2.5 Exposure and Waist-Hip Ratio on Non-Alcoholic Fatty Liver Disease Risk in a...

Epidemiological studies have established a connection between environmental factors and the prevalence of non-alcoholic fatty liver disease (NAFLD). Fine particulate matter with an aerodynamic diameter ≤ 2.5 μm (PM_2.5), a major component of ambient air pollution, has been implicated in systemic inflammation and metabolic dysfunction. The waist-hip ratio (WHR), an important measure of body composition, is a key risk factor for metabolic syndrome and NAFLD. We investigated the association between ambient PM_2.5 exposure, WHR, and NAFLD. We used data from the Taiwan Biobank collected between 2016 and 2020, involving 15,049 individuals aged 30 to 70 years. Ambient PM_2.5 exposure was estimated using a land-use regression model and categorized into quartiles. NAFLD was identified using liver function tests and imaging, and WHR was classified as normal or abnormal based on sex-specific cutoffs. Participants with NAFLD (n = 7179) had higher body mass index, a greater prevalence of abnormal WHR, and less favorable lipid profiles compared with those without NAFLD (n = 7870). Higher PM_2.5 exposure was associated with increased odds of NAFLD, with participants in the highest quartile (PM_2.5 > 39.85 μg/m³) showing an odds ratio (OR) of 1.251 (95% CI: 1.114-1.404). An abnormal WHR was also associated with higher odds of NAFLD (OR = 1.641, 95% CI: 1.507-1.787). A statistically significant interaction between PM_2.5 exposure and WHR was observed, with individuals with abnormal WHR exhibiting consistently higher odds of NAFLD across all PM_2.5 quartiles. In the highest PM_2.5 quartile, participants with abnormal WHR had an OR of 2.020 (95% CI: 1.708-2.389), compared with an OR of 1.442 (95% CI: 1.215-1.712) among those with normal WHR. These findings suggest that central obesity may amplify the association between PM_2.5 exposure and NAFLD, highlighting the importance of integrated public health strategies targeting both air pollution and metabolic health.