A number of studies have demonstrated the cognitive, physiological, and social benefits of time spent in the great outdoors, but a new Canadian study suggests that living in greener environments can actually affect how long you live.
Dr. Dan Crouse, an epidemiologist and sociology research associate at the University of New Brunswick, with a team of researchers from across Canada and the United States, published findings in this month’s issue of The Lancet Planetary Health. The study’s purpose was to see how everyday exposures to greenness affected mortality patterns.
While many scientific studies have demonstrated other positive health benefits of exposure to natural environments, very few have examined its potential effect on the risk of mortality, and this is the largest study to date.
“We found shockingly protective effects associated with increased exposure,” says Dr. Crouse. “The size of effects we found were much stronger than what we expected.” The researchers found that living in greener areas within Canadian cities was associated with an eight to 12 per cent reduced risk of dying from several common causes of death, including cardiovascular and respiratory diseases.
The study, Urban Greenness and Mortality in Canada’s Largest Cities: A National Cohort Study, used a national cohort of 1.3 million Canadians living in 30 cities across the country over an 11-year period.
Taking into account the amount of trees, plants, shrubs, and various other vegetation within 250 metres of each individual’s home, the researchers created estimates of daily “greenness” exposure. Personal characteristics of the subjects were taken into account, as well as data related to the communities where they lived, such as socioeconomic makeup and environmental characteristics like air pollution and population density.
Interestingly, researchers found that the protective effects of green space exposure weren’t the same for everyone. Subjects with higher incomes and more education tended to live in the greenest urban areas, and the researchers also found notably more protective effects among these groups. This suggests that more affluent and better educated people tended to experience not only greater exposures to greenness, because they could afford it, but also greater benefits to their health.
For these high-income individuals, more green means cleaner air, less noise from traffic, and cooler temperatures, which all leads to reduced stress, better sleep and higher levels of mental functioning.
In contrast, findings showed that low-income individuals with the same amounts of exposure to greenness would not necessarily receive the same benefits. In fact, among the poorest people, greenness seemed to offer no benefit and no reduction in risk of dying — however, the reasons why would require further study.
“The idea that urban green space may not benefit everyone equally could have some interesting implications for public health policy,” says Dr. Crouse. Such implications may relate to both the quantity and quality of green spaces in different parts of cities, or to facilitate more equal access and potential exposures.
The findings may also be of interest to urban and city planners who are responsible for building and managing cities’ green spaces.
For example, planting new trees throughout a city, on medians and along sidewalks, could produce benefits to health different from those associated with expanding parks or other localized green spaces.
The study didn’t look at the effects of green space on people living in rural areas, however, urbanites tend to be healthier than rural dwellers because of higher levels of education, lower smoking rates and body mass indexes, and more access to jobs and services.
“What we were trying to get at with this study was how greenness might act as a buffer against the stresses of urban living, like air pollution, traffic, noise and heat,” says Dr. Crouse.
“The study suggests that there’s a real health benefit to general community greening. That investment certainly seems worth it if it can be made wisely.”
Media contact: Hilary Creamer Robinson
Photo: Dr. Dan Crouse, epidemiologist and sociology research associate at the University of New Brunswick. Credit: Rob Blanchard / UNB Photo.