Residential green and blue spaces with nonalcoholic fatty liver disease incidence: Mediating effect of air pollutants

Abstract

Background: This study aimed to investigate the relationship of residential green and blue spaces with incident nonalcoholic fatty liver disease (NAFLD), and explore the potential mediation effects of air pollutants and modification effect of genetic susceptibility. Methods: 411,200 UK Biobank participants without prior liver diseases were included. Land use data were used to estimate residential green and blue spaces (land coverage percentage) at 300 m and 1000 m buffer. The study outcome was incident NAFLD, ascertained through linkage to hospital admissions and death registry records. Results: 5198 NAFLD cases were documented after a median follow-up of 12.5 years. Green and blue spaces were inversely associated with the hazard of NAFLD: per standard deviation (SD) increment of green space coverage at 300 m (SD: 14.5 %; HR, 0.88, 95 %CI, 0.86–0.91) and 1000 m (SD: 14.1 %; HR, 0.88, 95 %CI, 0.86–0.91) buffer, and blue space coverage at 300 m (SD: 1.0 %; HR,0.95, 95 %CI, 0.93–0.98) and 1000 m (SD: 1.2 %; HR,0.96, 95 %CI, 0.93–0.99) buffer were related with a 4–12 % reduction of NAFLD incidence. The beneficial effects of approximately 25–52 % of green space exposure and about 5–35 % of blue space exposure on NAFLD incidence were mediated by the reduction of PM2.5, NO2 and NOx (All P indirect effect <0.05). Moreover, genetic susceptibility of NAFLD did not modify the relationship of green and blue spaces with NAFLD incidence. Conclusion: Residential green and blue spaces were inversely related to NAFLD incidence. These results suggest that green and blue spaces are modifiable factors that may help prevent NAFLD, and therefore, can be considered as a novel environmental strategy to promote liver health at the community level, rather than only at the individual level.

Keywords

• Green space
• Blue space
• NAFLD
• Air pollutants
• Genetic susceptibility
• UK biobank