Local Improvements in Greenspace Decrease Cardiovascular Hospital Admissions
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Background: Comparisons of greenspace between metropolitan areas generally reflect regional differences in soil characteristics and climatic zone, while greenspace variation within a metropolitan area at the postal code level avoid these regional differences. We examined local variations in greenspace as determinants of local variation in cardiovascular hospital admission rates (CHR).
Methods: We calculated annual age-adjusted CHR among Medicare beneficiaries aged 65 years and older for 2002-2013 across 10,097 ZIP codes (postal codes) in 123 major metropolitan core-based statistical areas (CBSA). We obtained monthly normalized difference vegetative index (NDVI) on a 1km x 1km grid from the Terra satellite, mapped this data to metropolitan ZIP code shapefiles, determined the month with maximum NDVI for each metropolitan area, and finally assigned maximum annual values of NDVI for each ZIP code and year. Finally, we modeled the associations scaled to the interquartile range (IQR) both for centered means and for 12-year trends in CHR and NDVI, adjusting for CBSA and for levels and trends in adjusted gross income, proportion White and population density.
Results: Across major US metropolitan areas for 2002-2013, CHR had a mean of 5,903 admissions per 100,000 person-years at risk and a trend of -122 per year. An IQR increment of 0.121 in the mean NDVI was associated with a 52.4 lower CHR (95% CI 20.4, 84.3), while an IQR increment of 0.018 in the annual trend in NDVI was associated with a 6.4 per year greater decrease in CHR (95% CI 4.5, 8.3).
Conclusion: Thus, after adjustment for metropolitan area characteristics and for local variations in cardiovascular risk factors, we have shown that local improvements in greenspace (NDVI) lead to local improvements in cardiovascular health among Medicare beneficiaries.
This abstract does not necessarily represent the views or policies of the U.S. Environmental Protection Agency.