Does long-term green space exposure improve hypertension and blood pressure? The Henan rural cohort study

Background: Growing epidemiological evidence has demonstrated green space could be a protective factor to high blood pressure. However, the evidence is very limited in China. We aimed to investigate the associations in a Chinese rural population. Methods: We did a cross-sectional study using baseline data of 39,259 participants from the Henan Rural Cohort study. Community greenness exposure was assessed using two satellite- derived vegetation indexes - the Normalized Difference Vegetation Index (NDVI) and the Enhanced Vegetation Index (EVI). The spatiotemporal model was employed to estimate the individual exposure to the particulate matter with aerodynamic diameter ≤ 2·5 μm (PM2·5). Hypertension and blood pressure were assessed using the standardized protocol. We used the generalized linear mixed models to investigate the associations of community greenness with hypertension and blood pressure. Findings: An interquartile range (IQR) increase in NDVI 500m was significantly associated with 8% decrease in odds of hypertension (OR= 0·92, 95% CI: 0·88, 0·95), a reduction in systolic blood pressure (SBP) of 0·88 mmHg (95% CI: -1·17, - 0·58), and a reduction in diastolic blood pressure (DBP) of 0·64 mmHg (95% CI: - 0·82, - 0·46) , respectively. Subgroup analysis showed that the effects of greenness are more pronounced in males, smokers, drinkers, and people exposed to the lowest quartile PM2·5. Interpretation: Higher community greenness exposure was associated with lower odds of hypertension and blood pressure in the Chinese rural population, and the association was affected by behavioral and environmental factors. Trial Registration: The Henan Rural Cohort study (Registration number: ChiCTR-OOC-15006699). Funding Statement: This work was funded by the National Key Research and Development Program of China (2016YFC0900803); the National Natural Science Foundation of China (81903279); the Bill & Melinda Gates Foundation (OOP1148464); and the Hubei Province Natural Science Foundation (2018CFB634). YG was supported by the Career Development Fellowship of the Australian National Health and Medical Research Council (APP1107107). SL was supported by the Early Career Fellowship of Australian National Health and Medical Research Council (APP1109193) Declaration of Interests: The authors declare no competing interests. Ethics Approval Statement: The study was approved by the Ethics Committee of Zhengzhou University and Wuhan University. Written informed consent was obtained before the survey and physical examination.