Friday, April 15, 2016, 11:00 a.m. EDT
Women live longer in areas with more green vegetation, according to new research funded by the National Institute of Environmental Health Sciences (NIEHS), part of the National Institutes of Health. Women with the highest levels of vegetation, or greenness, near their homes had a 12 percent lower death rate compared to women with the lowest levels of vegetation near their homes. The results were published Apr. 14 in the journal Environmental Health Perspectives.
The researchers found the biggest differences in death rates from kidney disease, respiratory disease, and cancer. The researchers also explored how an environment with trees, shrubs, and plants might lower mortality rates. They showed that improved mental health and social engagement are the strongest factors, while increased physical activity and reduced air pollution also contribute.
"It is important to know that trees and plants provide health benefits in our communities, as well as beauty," said NIEHS director Linda Birnbaum, Ph.D. "The finding of reduced mortality suggests that vegetation may be important to health in a broad range of ways."
The study, conducted by scientists at Harvard T.H. Chan School of Public Health and Brigham and Women's Hospital in Boston, examined greenness around the homes of 108,630 women in the long-term Nurses' Health Study. The researchers mapped home locations and used high resolution satellite imagery to determine the level of vegetation within 250 meters and 1,250 meters of homes. They then followed the women from 2000 to 2008, tracking changes in vegetation and participant deaths. During the study, 8,604 deaths occurred.
The scientists consistently found lower mortality rates in women as levels of trees and plants increased around their homes. This trend was seen for separate causes of death, as well as when all causes were combined. When researchers compared women in the areas with highest greenness to women in the lowest, they found a 41 percent lower death rate for kidney disease, 34 percent lower death rate for respiratory disease, and 13 percent lower death rate for cancer in the greenest areas.
"The ability to examine vegetation in relatively fine detail around so many homes, while also considering the characteristics of the individual participants, is a major strength of this study," said Bonnie Joubert, Ph.D., NIEHS scientific program director overseeing the study. "This builds on prior studies showing the health benefits of greenness that used community-level or regional data."
The scientists also looked at characteristics that can otherwise contribute to mortality risk, such as age, race, ethnicity, smoking, and socioeconomic status. This enabled them to be more confident that vegetation plays a role in reduced mortality, rather than these factors. If participants moved or the vegetation near their homes changed during the study, the scientists took those changes into account in their study.
Reference: James P, Hart JE, Banay RF, Laden F. Exposure to greenness and mortality in a nationwide prospective cohort study of women. Environmental Health Perspectives; doi:10.1289/ehp.1510363 [Online 14 Apr 2016].
About the National Institute of Environmental Health Sciences: NIEHS supports research to understand the effects of the environment on human health and is part of NIH. For more information on environmental health topics, visit http://www.niehs.nih.gov. Subscribe to one or more of the NIEHS news lists (http://www.niehs.nih.gov/news/newsroom/newslist/index.cfm) to stay current on NIEHS news, press releases, grant opportunities, training, events, and publications.
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