Who benefits from green spaces? Surrounding greenness and incidence of cardiovascular disease in a population-based electronic medical records cohort in Madrid.

The objective was to study the association between surrounding greenness and the incidence of cardiovascular diseases (CVD) with a four years follow-up in almost half a million high CVD-risk women and men, as well as its differential effect by area-level deprivation in Madrid. We analyzed 2015-2018 primary healthcare electronic medical records for 437,513 high CVD risk individuals representing more than 95% of the population of that age range residing in Madrid. The outcome variable was any cardiovascular event. We measured surrounding residence greenness at 200 m, 300 m, 500 m, and 1000 m through the Normalized Difference Vegetation Index (NDVI). We assessed socioeconomic deprivation through a census-based deprivation index. We estimated the 4-year relative risk of CVD by an increase in 0.1 units of NDVI and then stratified the models by quintiles of deprivation (Q5 the most deprived). We found that for every increase in 0.1 units of NDVI at 1000 m there was a 16% decrease in CVD risk (RR = 0.84 95% CI 0.75-0.94). CVD risk for the remaining distance exposures (at 200 m, 300 m, and 500 m) were none statistically significant. In general, the protective effect of green spaces was present in medium-deprivation areas and males, but the associations were inconsistent across deprivation levels. This study highlights the relevance of evaluating the interaction between physical and social urban components to further understand possible population prevention approaches for cardiovascular diseases. Future studies should focus on the mechanisms of context-specific interactions between social inequalities and green spaces' effects on health.