Association of greenness with incidence of cardiovascular disease in China: Evidence from the China Kadoorie Biobank prospective cohort study with 0.5 million adults

Prospective evidence on the relationship of greenness with cardiovascular disease (CVD) incidence is limited in low- and middle-income countries. In 512,691 participants of the China Kadoorie Biobank cohort across 10 regions in China, we calculated the levels of greenness exposure based on satellite-retrieved Normalized Difference Vegetation Index (NDVI) data. Annual maximum NDVI (NDVI_max) values were estimated within 500 ​m and 1000 ​m buffers around the locations for the participants during the follow-up periods. Record linkages to healthcare databases provided incidence data of total CVD, ischemic heart disease and stroke during 2005-2017. Time-varying Cox proportional hazards regression was used to assess the associations between greenness exposure and CVD incidence. After 5.08 million person-years of follow-up, 148,032 incident CVD events were recorded. The overall average level of NDVI_max was 0.543 for all participants. We observed significant inverse associations of greenness with the incidence of CVD and its subtypes. Specifically, the hazard ratio for total CVD incidence was 0.976 (95% confidence interval: 0.958, 0.994) per 0.1 increase in NDVI_max within a 500 ​m buffer. As the 5 rural regions have achieved the WHO recommended greenness goal values, we compared the greenness levels in the 5 urban regions with the WHO's goal for greenness and found that, on average, 3.81% of total CVD incidence might be averted if the recommended greenness values could be achieved. Exposure to a higher level of greenness was associated with a lower risk of CVD incidence in Chinese adults.