The contribution of residential greenness to mortality among men with prostate cancer: a registry-based cohort study of Black and White men

Background: Black men with prostate cancer (CaP) experience excess mortality compared with White men. Residential greenness, a health promoting contextual factor, could explain racial disparities in mortality among men with CaP. Methods: We identified Pennsylvania Cancer Registry cases diagnosed between January 2000 and December 2015. Totally, 128,568 participants were followed until death or 1 January 2018, whichever occurred first. Residential exposure at diagnosis was characterized using the Normalized Difference Vegetation Index (NDVI) with 250 m resolution. We estimated hazard ratios (HRs) using Cox models, adjusting for area-level socioeconomic status, geographic healthcare access, and segregation. To determine whether increasing residential greenness could reduce racial disparities, we compared standardized 10-year mortality Black-White risk differences under a hypothetical intervention fixing NDVI to the 75th percentile of NDVI experienced by White men. Results: We observed 29,978 deaths over 916,590 person-years. Comparing men in the highest to lowest NDVI quintile, all-cause (adjusted HR [aHR]: 0.88, 95% confidence interval [CI]: 0.84, 0.92, P-trend < 0.0001), prostate-specific (aHR: 0.88, 95% CI: 0.80, 0.99, P-trend= 0.0021), and cardiovascular-specific (aHR: 0.82, 95% CI: 0.74, 0.90, P-trend < 0.0001) mortality were lower. Inverse associations between an interquartile range increase in NDVI and cardiovascular-specific mortality were observed in White (aHR: 0.90, 95% CI: 0.86, 0.93) but not Black men (aHR: 0.97, 95% CI: 0.89, 1.06; P-het = 0.067). Hypothetical interventions to increase NDVI led to nonsignificant reductions in all-cause (-5.3%) and prostate-specific (-23.2%), but not cardiovascular-specific mortality disparities (+50.5%). Discussion: Residential greenness was associated with lower mortality among men with CaP, but findings suggest that increasing residential greenness would have limited impact on racial disparities in mortality.