Association between green space and hepatocellular carcinoma risk: a retrospective cohort study of seven South Korean metropolitan areas

This longitudinal study evaluated the association between urban green space density and hepatocellular carcinoma (HCC) in seven metropolitan cities of South Korea. Information on study participants was extracted from the Korea National Health Insurance Service database. The study population comprised 104,527 participants aged ≥ 40 years who underwent biennial health screening examinations between 2009 and 2010. Based on land use data retrieved from the Korean National Statistical Office, urban green space density was measured as the area of parks and artificially designed facilities per 1,000 people. Data on the incidence of new HCC were collected from medical treatment claims data from 1 January 2011 to 31 December 2019. Compared to those living in the lowest quartile of green space density, those residing in the highest quartile had a lower risk of HCC incidence (adjusted hazard ratio: 0.71, 95% confidence interval: 0.53–0.96). The effect of green space density on reducing HCC risk was especially significant among participants who did not have prior competing liver disease or who did not drink alcohol. An average 18.53 m² per capita in urban green space density resulted in a 29% decrease in the incidence of HCC.