Mortality and 15-min green space access across urbanicity levels in China

Previous studies investigating the health benefits of green space primarily focused on its quantity, while individual accessibility has been insufficiently considered. This study aimed to investigate the associations between green space within accessible isochrones and mortality and the effect modification by regional urbanicity. Using a nationally representative survey of 47,086 participants with prospective death records according to ICD-10 codes (up to December 2017) and high spatial-resolution remote sensing data, this cohort study investigated the associations of green space (characterized using green land cover proportion and the Normalized Difference Vegetation Index [NDVI]) within 15-min walking and cycling isochrones with all-cause and cause-specific (cardiovascular disease, respiratory disease, and cancer) mortality. We also explored the associations across regions with different levels of urbanicity-related built environment factors using interaction models. Green space within 15-min walking and cycling isochrones was associated with lower risks of mortality. For instance, a 10 % increase in green land cover proportion within 15-min isochrones was associated with 5 % (hazard ratio [HR] = 0.95, 95 % CI: 0.90, 1.00 for walking) and 12 % (HR = 0.88, 95 % CI: 0.81, 0.96 for cycling) reductions in all-cause mortality risk. Stronger protective effects of green space on mortality were found in areas with higher nighttime light index (NLI), population density, road density, and impervious land cover proportion (P for interaction <0.05). Similar effect modification by urbanicity-related built environment factors was also found for associations of green space with cardiovascular disease mortality. Accessible green space within 15-min walking and cycling regions was associated with lower mortality risks, especially in regions with higher urbanicity levels. The findings underscore the importance of considering both the accessibility of green space and regional urbanicity in land planning to maximize the health benefits of green space.