The University of Louisville’s groundbreaking Green Heart Louisville Project found that people who lived in neighborhoods where the number of trees and shrubs had more than doubled showed lower levels of a blood marker of inflammation than those who lived outside planted areas. General inflammation is a key risk indicator for heart disease and other chronic diseases.
The Christina Lee Brown Envirome Institute launched the first project of its kind in 2018 in collaboration with The Nature Conservancy, Washington University in St. Louis, Hyphae Design Laboratory and others to investigate whether and how living in a denser green environment contributes to better heart health. The design of the study closely resembles clinical trials that test whether medical treatments are effective. The team applied the treatment – the addition of large trees and shrubs – to the neighborhoods of some participants, but not others. They then compared residents’ health data to see how the addition of the trees affected their health.
“The Green Heart Louisville Project is an excellent example of how our university’s innovative and collaborative researchers are working to improve lives in our community and beyond,” said UofL President Kim Schatzel. “Trees are beautiful, but these results show that the trees around us also benefit the health of individuals and communities. Through this and many other projects, the Envirome Institute improves health at the community level, not just for individuals, but for everyone who lives. in a neighborhood.”
To understand the health status of the community at the start of the study, researchers took blood, urine, hair and nail samples and documented health data from 745 people living in a four-square-mile area of southern Louisville. The researchers also took detailed measurements of tree cover and air pollution levels in the area.
Following this baseline data collection, the Envirome Institute worked with The Nature Conservancy and a host of local partners and contractors to plant more than 8,000 large trees and shrubs in designated neighborhoods within the project area. Those living in the green area were considered the treated population and the results of this population were compared with residents of adjacent neighborhoods, where the project team did not plant trees.
After the planting, the research team reassessed the health of the residents. They found that those who lived in the green area had 13-20% lower levels of a biomarker for general inflammation, a measure called high-sensitivity C-reactive protein (hsCRP), than those who lived in the areas where there were no new trees or trees came. shrubs. Higher levels of hsCRP are strongly associated with a risk of cardiovascular disease and are an even stronger indicator of heart attack than cholesterol levels. Higher CRP levels also indicate a higher risk of diabetes and certain cancers.
A reduction in hsCRP by this percentage equates to a nearly 10-15% reduction in the risk of heart attacks, cancer or death from any disease.
“These results from the Green Heart Louisville Project indicate that trees contribute more to our lives than beauty and shade. They can improve the health of those around them,” said Aruni Bhatnagar, director of the Envirome Institute and professor of medicine at the UofL. “Although several previous studies have found a link between living in areas with lots of greenery and health, this is the first study to show that a deliberate increase in greenery in the neighborhood can improve health. With these results and additional studies, we hope to We will soon gain a better understanding of the impact of local tree cover on the health of residents.’
As more is known about the health consequences of increased forest cover, increased greening in cities may prove to be an important method to improve public health.
“Most of us intuitively understand that nature is good for our health. But scientific research that tests, verifies and evaluates this connection is rare,” said Katharine Hayhoe, chief scientist at The Nature Conservancy. “These recent findings from the Green Heart Project make the scientific case for the powerful connections between the health of our planet and the health of us all.”
Earlier in August, the Green Heart Louisville Project was awarded an additional $4.6 million in funding from the National Institute of Environmental Health Sciences to support continued research over the next five years.
These findings were presented by Daniel Riggs, assistant professor of environmental medicine at UofL, at the 36th annual conference of the International Society for Environmental Epidemiology in Santiago, Chile on August 26.
