Residential greenness associated with decreased risk of metabolic- dysfunction-associated fatty liver disease: Evidence from a large population-based epidemiological study

Background: Numerous studies have shown that residential greenness positively correlates with enhanced health. Metabolic dysfunction-associated fatty liver disease (MAFLD) affects about a quarter of the population while lacking specific treatments. Given that the association between green space and MAFLD is still unknown, we explored the association between residential greenness and MAFLD as well as the potential mechanisms based on the baseline survey of the China Multi-Ethnic Cohort (CMEC). Methods: Residential greenness was expressed as normalized difference vegetation index (NDVI) and enhanced vegetation index (EVI). MAFLD was assessed through hepatic steatosis, the presence of overweight/obesity, type 2 diabetes mellitus, and evidence of metabolic dysregulation. We used logistic regression to examine the association between NDVI/EVI and the prevalence of MAFLD. Moreover, we utilized causal mediation analyses to explore the role of physical activity and ambient particulate matters (PM1, PM2.5, and PM10) on the association between residential greenness and MAFLD. Results: We included 72,368 participants from the CMEC and found that residential greenness was negatively associated with the prevalence of MAFLD. For an interquartile range (IQR) increase in NDVI500 m and EVI500 m, the odds ratio (OR) of MAFLD were 0.78 (95 %CI: 0.75, 0.81) and 0.81 (95 %CI: 0.78, 0.84), respectively. Greater association between residential greenness and MAFLD was observed among males. Air pollutants and physical activity could mediate a partial effect (8.5–22.9 %) of residential greenness on MAFLD. Conclusion: Higher residential greenness was associated with decreased risk of MAFLD. Moreover, the association was greater among males. The protective effects of residential greenness may be achieved by mitigating the hazardous effects of air pollutants and encouraging physical activity.