AS386 - Natural environment and cardiovascular incidence and mortality: The WHI
[This page is intended to provide a study summary, the sections of which are below. Please complete these sections, as applicable. The headings below are suggested headings. You can remove inapplicable sections, or add new ones relevant to your study]
Investigator Names and Contact Information
Geoffrey Donovan [ gdonovan@fs.fed.us ]
Introduction
Evidence from multiple scientific fields supports the theory that exposure to the natural environment can improve human health. Pioneering work in the field was done by Ulrich [1], who found that patients recovering from gall-bladder removal surgery in a room with a view of a natural scene recovered faster and took fewer pain medications than patients in a room with a view of a brick wall. Extending Ulrich's work has been problematic, because most health outcomes of interest have causes that go back much longer than a short surgical recovery, and most people spend little time in environments as controlled as a hospital room. However, subsequent observational studies provide support for a negative association between exposure to the natural environment (sometimes measured as exposure to "greenness") and a broad range of health outcomes, including mortality [2, 3], stroke [4], asthma [5], birth outcomes [6, 7], attention-deficit disorder [8], and obesity [9]. Experimental work has focused on the short-term effect of the natural environment on intermediate markers of health such as blood pressure or cortisol levels [10-12]. However, the majority of existing research is limited by cross-sectional study design and a failure to adequately address confounding factors [13]. Quasi-experimental designs are needed to provide stronger evidence of a causal link between the natural environment and health.
An introduced beetle, the emerald ash borer, has killed tens of millions of ash trees since it was first detected in the United States in 2002. The spread of emerald ash borer is a unique natural experiment that allows us to quantify the impact of a significant change in the natural environment on public health. We recently completed an analysis of county-level mortality [14] in which we found a significant association between the spread of emerald ash borer and county-level cardiovascular and lower-respiratory mortality. The magnitude of this effect was greater as an infestation progressed and in counties with above average median-household income. Across the 15 states in our study area, emerald ash borer was associated with 6,113 additional lower-respiratory deaths and 15,080 cardiovascular deaths. Our results suggest that trees are associated with reduced risk of mortality due to cardiovascular and lower-respiratory disease.
Although several studies including ours have identified a link between the natural environment and health, the mechanisms of this relation are far from clear. There are plausible mechanisms linking cardiovascular and lower-respiratory disease with trees. Specifically, the natural environment has been shown to decrease stress [10], increase physical activity [15], and improve air quality [16]. In turn, stress [17, 18], physical activity [19, 20], and air quality [21] have been linked with cardiovascular and lower-respiratory disease.
Data from the WHI would allow us to conduct a far richer analysis of the effect of the emerald ash borer on individual health. We would also be able to study the effect of the natural environment on different demographic groups, which is an important opportunity, as past research suggests that the natural environment may provide greater benefits to people with lower socio-economic status [22] and, in particular, women with lower socio-economic status [6]. Finally, WHI data would allow us to examine the mechanisms linking the natural environment and health. Specifically, we will conduct analyses to address the following aims:
Specific Aims:
- To quantify the relation between emerald ash borer and cardiovascular disease.
- To evaluate the degree to which the association between emerald ash borer and cardiovascular disease is modified by socio-demographic characteristics.
References
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2. Mitchell, R. and F. Popham, Effects of exposure to natural environment on health inequalities: an observational population study. Lancet, 2008. 372: p. 1655-60.
3. Takona, T., K. Nakamura, and M. Wattamabe, Urban residential environments and senior citizens' longevity in megacity areas: the importance of walkable green
spaces. Journal of Epidemiology and Community Health, 2002. 56(12): p. 913-918.
4. Hu, Z., J. Liebens, and K.R. Rao, Linking stroke mortality with air pollution, income, and greenness in northwest Florida: an ecological geographical study. International
Journal of Health Geographics, 2008. 7(20): p. 1-22.
5. Lovasi, G.S., et al., Children living in areas with more street trees have lower prevalence of asthma. J Epidemiol Community Health, 2008. 62(7): p. 647-649.
6. Dadvand, P., et al., Green space, health inequality and pregnancy. Environment International, 2012. 44(1): p. 3-30.
7. Donovan, G.H., et al., Urban trees and the risk of poor birth outcomes. Health and Place, 2011. 17: p. 390-393.
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10. Park, B.-J., et al., Physiological effects of shinrin-yoku (taking in the atmosphere of the forest) in a mixed forest in Shinano Town, Japan. Scandanavian Journal of Forest
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13. Lee, A.C. and R. Maheswaran, The health benefits of urban green spaces: a review of the evidence. J Public Health (Oxf), 2011. 33(2): p. 212-22.
14. Donovan, G.H., et al., The relation between trees and human health: evidence from the spread of the emerald ash borer. Environmental Health Perspectives, In Review.
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19. Oguma, Y. and T. Shinoda-Tagawa, Physical activity decreases cardiovascular disease risk in women: Review and meta-analysis. American Journal of Preventive
Medicine, 2004. 26(5): p. 407-418.
20. Lucas, S.R. and T.A.E. Platts-Mills, Physical activity and exercise in asthma: Relevance to etiology and treatment. Journal of Allergy and Clinical Immunology, 2005.
115(5): p. 928-934.
21. Pope, C.A., et al., Cardiovascular Mortality and Long-Term Exposure to Particulate Air Pollution. Circulation, 2004. 109: p. 71-77.
22. Maas, J., et al., Morbidity is related to a green living environment. J Epidemiol Community Health, 2009. 63(12): p. 967-73.
