Kaiser Permanente study finds health care system costs were lower for people who live in greener areas
By Sue Rochman
Nature’s benefits may include savings on health care costs, a new Kaiser Permanente study found.
The research, published in Environment International, suggests health care systems may spend hundreds of dollars less per person per year on medical care for people living in neighborhoods with the most green space than they do on those living near the least trees, shrubs, and grass.
“Our study showed that across the whole range of neighborhoods there was a consistent pattern between living in areas with more green space and lower health care costs,” said the study’s lead author Stephen K. Van Den Eeden, PhD, a research scientist at the Kaiser Permanente Northern California Division of Research. “We believe the findings suggest that expenditures on medical care may be hundreds of dollars more each year for people living in neighborhoods with less green space.”
The researchers used Normalized Difference Vegetation Index (NDVI) satellite data to determine the amount of green space within 250, 500, and 1,000 meters (820, 1,640, and 3,280 feet) of the home address of more than 5 million people who were Kaiser Permanente Northern California members for at least 2 years between 2003 and 2015. Then, they used data from the Fire and Resource Assessment Program, a measure of the tree canopy that is used for fire risk management, as a second measure of greenspace.
Next, they determined the individual care costs for each patient. The costs they used in their analysis reflected how much Kaiser Permanente, an integrated health care delivery system, spent to care for each patient, not how much each individual spent. In their analyses, the researchers took into account age, gender, race/ethnicity, air quality, and extensive neighborhood characteristics such as income, education level, housing density, and population density.
The study found that, on average, people who lived near greater amounts of green space were more likely to be older, male, white, and have higher income and education levels. But even after taking this into account, the research showed the annual average health care cost was $374 lower per person per year for those living near the most green space than it was for those living near the least green space.
“Our study adds to the growing body of literature that has found living in greener areas is tied to beneficial short- and long-term health outcomes,” said the study’s co-author Matthew H.E.M. Browning, PhD, an assistant professor at Clemson University in South Carolina. “The mechanisms linking nature and health are very diverse, but the benefits are believed to be in part because being in green space can decrease stress, promote healthy behaviors, and improve air quality.”
The findings support ongoing public policy efforts to add more green space to residential areas. “Our study supports an investment in urban greening for preventive health as well as all the other collateral benefits green space has to offer,” added Browning.
Van Den Eeden said that although the study could show only an association and not causation, it was important to note that they had accounted for the known factors that could sway the results. “We put everything into the model that might explain the findings — demographic variables, socioeconomic variables, population density — and none of it makes the association go away. We feel about as confident of our findings as you can be for this type of study.”
The study was funded by the U.S. Forest Service’s Urban and Community Forest Grant Program within the Department of Agriculture.
Co-authors include Jun Shan, PhD, Stacey E. Alexeeff, PhD, G. Thomas Ray, MBA, and Charles P. Quesenberry, PhD, at the Division of Research and Douglas Becker, PhD, and Ming Kuo, PhD, at the University of Illinois, Urbana-Champaign.
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About the Kaiser Permanente Division of Research
The Kaiser Permanente Division of Research conducts, publishes and disseminates epidemiologic and health services research to improve the health and medical care of Kaiser Permanente members and society at large. It seeks to understand the determinants of illness and well-being, and to improve the quality and cost-effectiveness of health care. Currently, DOR’s 600-plus staff is working on more than 450 epidemiological and health services research projects. For more information, visit divisionofresearch.kaiserpermanente.org or follow us @KPDOR.