Residential urban greenspace and hypertension: a comparative study in two European cities

Background: Living in green areas has been associated with several health benefits; however, the available evidence on such benefits for hypertension is still limited. This study aimed to investigate and compare the association between residential exposure to greenspace and hypertension in Barcelona, Spain and Brussels, Belgium. Methods: This cross-sectional study was based on data from the 2016 Barcelona Health Interview Survey (HIS) (n = 3400) and the 2013 Belgian HIS (n = 2335). Both surveys were harmonized in terms of outcomes, confounders and exposure assessment. Residential exposure to greenspace was characterized as 1) surrounding greenspace (normalized difference vegetation index (NDVI) and modified soil-adjusted vegetation index 2 (MSAVI2)) across buffers of 100 m, 300 m, and 500 m; 2) surrounding green space across 300 m and 500 m buffers; and 3) Euclidean distance to the nearest green space. Our outcome was self-reported hypertension. We developed logistic regression models to evaluate the city-specific association between each greenspace measure and hypertension, adjusting for relevant covariates. Results: One interquartile range (IQR) increase in residential distance to the nearest green space was associated with higher risk of hypertension in Barcelona [odds ratio (OR): 1.15; 95%CI 1.03-1.29 (IQR: 262.2)], but not in Brussels [OR: 0.95; 95%CI 0.77-1.17 (IQR: 215.2)]. Stratified analyses suggested stronger associations in older participants (≥65 years) for both cities. Findings for residential surrounding green space and greenspace were not conclusive. However, in Brussels, we found protective associations in older participants for both residential surrounding greenspace metrics [NDVI 300 m buffer OR: 0.51; 95%CI 0.32-0.81 (IQR: 0.21) and MSAVI2 300 m buffer OR: 0.51; 95%CI 0.32-0.83 (IQR: 0.18)]. We did not find any indication for the modification of our evaluated associations by sex and education level. Conclusion: Our study suggests that living closer to greenspace could be associated with lower risk of hypertension, particularly in older age. Future research is needed to replicate our findings in other settings and shed light on potential underlying mechanism(s).MB is funded by an individual PhD grant supported by the Research Foundation - Flanders (FWO) (grant number 11A9718N) and a Gustave Boël - Sofina Fellowship (grant number V422218N). WLZ is supported by a Sara Borrell grant from the Instituto de Salud Carlos III (CD17/00195). PD is funded by a Ramón y Cajal fellowship (RYC-2012-10995) awarded by the Spanish Ministry of Economy and Financ