The ArcGIS GridExtract add-in module was used to assign NDVI grid-cell estimates to each residential address. We used NDVI estimates from the month of July since this month represents the period of most substantial vegetation growth in the greater Boston area and therefore typically reflects the maximum possible green space in each grid cell (Breckle, 2002). We calculated the average NDVI levels for all July estimates between 2000 (when the data first became available from NASA) and 2012 (the end of mortality follow-up period). In each year, there were two July NDVI measures for each cell, providing a total of 26 measures from 2000 to 2012. Estimates were available for all grid cells in all years and there were no missing data.