Moving to greener neighborhoods and healthcare costs in Northern California
Background: Environmental drivers of healthcare costs are mainly unknown. Studies that account for changes in longitudinal, within-individual changes accompanying changes in residential addresses have not been conducted. In the current study, we tested whether moving to a greener neighborhood was associated with decreases in healthcare costs and whether these associations vary by individual and neighborhood-level characteristics. Methods: Cohort study with 13-year administrative data from Kaiser Permanente Northern California members who moved (N = 129,576) and did not move (N = 4,807,135). Healthcare costs and neighborhood characteristics before and after residential moves were examined, considering age, sex, race, neighborhood socioeconomic status, air pollution, and population density. Change in neighborhood greenery was measured as changes in deciles of satellite-derived Normalized Difference Vegetation Index (NDVI) in 250-m, 500-m, and 1000-m Euclidean buffers. Nonmovers were retained for analyses as they represented individuals with no changes in neighborhood greenery. Results: We found that moving to greener neighborhoods was generally not associated with changes in healthcare costs. However, moving to greener areas was associated with decreases in outpatient costs (NDVI-250-m relative cost ratio [RCR] = 0.993, 95% confidence interval [CI] = 0.987, 0.999). Movers with the greatest increase in greenness had $89 less annual outpatient costs than movers who maintained their greenness levels. Subgroup analyses found significant decreases in outpatient costs for women (RCR = 0.992, CI = 0.985,0.999), adults aged 18-44 (RCR = 0.989, CI = 0.981,0.996), and individuals moving from lower population density-neighborhoods (RCR = 0.991, CI = 0.983,0.999). Conclusions: This longitudinal, within-individual analysis found little evidence to support the hypothesis that moving to greener neighborhoods is associated with reduced healthcare spending. Future studies should incorporate data on duration of residence, individual socioeconomic status, reasons for moving, and broader economic outcomes to better evaluate how residential environments may influence healthcare costs.
