Volume 15, Number 7
Many factors affect health outcomes, defined as both the quality and length of life. A widely cited model used by the Robert Wood Johnson Foundation and the University of Wisconsin Population Health Institute in their annual County Health Rankings purports that several broad factors impact health outcomes in the following proportions: social and economic factors – 40%; health behaviors – 30%; clinical care – 20%; physical environment – 10%. The physical environment category includes the quality of air, water, housing, and transit.
It is increasingly evident that the amount of green space in one’s physical environment impacts health. There are numerous studies that have demonstrated short-term and long-term health benefits of being near (or being able to view) vegetation, including decreased stress, improved immune function, and better sleep. In urban areas, residents of neighborhoods with a higher density of trees are found to have fewer cardiovascular and metabolic health problems, even after controlling for socio-economic factors. A large Danish study that followed nearly a million children born between 1985 and 2003 found that growing up near green spaces was associated with a decreased incidence of mental and behavioral health problems in adulthood. This finding held even after controlling for urbanization, socio-economic factors, and the mental health of parents.
If living in the presence of green land cover is associated with better health, it should stand to reason that healthcare costs would be less for residents of such environments. A study recently published in Urban Forestry & Urban Greening attempted such an analysis. Examining over 30 million Medicare fee-for-service users in over 3000 US counties, the investigators found a small but significant association between county-wide prevalence of forest and shrub cover and decreased Medicare spending. The association was strongest in lower socio-economic status counties, particularly for the presence of forest cover. Of course, there can be much variation in the amount of green space in any given county (a weakness of this analysis) so it may be that more precise measures of green cover would identify an even stronger relationship between a green physical environment and health.
Across the studies that have examined a relationship between green space and health, it appears that the presence of trees (and forests) is more important than other types of vegetation. Trees can provide shade whereas smaller plants cannot, something that may help facilitate recreational activities and stress reduction in hot weather. Trees are also known to be associated with less concentration of air pollutants and decreased urban heat island effects.
Given that most persons find it subjectively pleasant to be in green spaces, it isn’t surprising that studies are finding that living in areas with more green cover, especially trees, is associated with better health. The value of such studies may be that they provide yet another reason to give attention to preservation of green spaces where possible, and reforestation efforts where indicated. And it may be that the presence of green is a more important component of the impact of the physical environment on health than has been appreciated to date.
Paul J. Hershberger, Ph.D.
… is a clinical health psychologist. He is Professor, Director of Research, and Director of the Division of Behavioral Health, Department of Family Medicine, Wright State University Boonshoft School of Medicine.
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