Long-term exposure to residential greenness and development of hypertension in Stockholm County

TPS 702: Green space and population health, Exhibition Hall, Ground floor, August 28, 2019, 3:00 PM - 4:30 PM Background/Aim: Experimental and observational studies occasionally report associations between urban greenness exposure and blood pressure levels. These findings are, however, inconsistent and few longitudinal studies exist. We report from an ongoing study of the association between objectively measured exposure to residential greenness and the development of hypertension, in a longitudinal setting. Methods: Based on the Stockholm Diabetes Prevention Program (SDPP) cohort, our study includes 3,493 normotensive subjects from Stockholm County aged 35-56 years at recruitment in 1992-1994. These were followed up 2002-2006 and 123 incident cases of hypertension were identified. Hypertension was defined as 140/90 mmHg or higher. We defined surrounding greenness as a time-weighted average of satellite-based Normalized Difference Vegetation Index (NDVI) at 30 m×30 m resolution during 1990-2015 in buffers of 250 m and 500 m around participants’ residential addresses. The association between NDVI and development of hypertension was estimated using Poisson regression models with adjustment for potential confounders at individual and contextual level. We also investigated NDVI in combination with exposure to different environmental factors. Ongoing analyses also include information from hospital register and questionnaires in relation to NDVI exposure during of 1, 5 and 10 years prior to diagnosed hypertension, analysed using Cox regression models. Results: No overall association between NDVI and development of hypertension was observed (IRR 0.98, 95% C.I. 0.76; 1.27, using the 500 m buffer). Analyses of combined exposures to low levels of NDVI, high levels of air pollution (NOx), transportation noise and long distance to water indicated positive associations, in particular low levels of NDVI and high levels of NOx appeared to be associated with development of hypertension among men. Conclusion: Preliminary investigations did not indicate any association between long-term greenness exposure and development of hypertension, but accentuated the importance of further investigations, in particular on effect modification by other environmental exposures.