by Living in a neighborhood full of trees and getting regular exercise may benefit the heart, new research shows.
Researchers at the University of Louisville designed a clinical trial that followed hundreds of people living in six low- to moderate-income neighborhoods in South Louisville, Kentucky. They used blood and other samples to better understand how their heart risks changed before and after the team planted thousands of mature trees near their homes.
Results from Louisville’s Green Heart Project HEAL Study, released Tuesday, showed that people living in neighborhoods with twice as many trees and shrubs had lower levels of a blood marker associated with heart disease, diabetes and some types of cancer compared to those who they lived in more treeless neighborhoods.
“We’re trying to see if we can reduce heart disease rates in a community,” said Aruni Bhatnagar, a professor of medicine at the University of Louisville, who led the project.
Most previous studies showing the effects of nature on mental and physical health are observational studies and cannot answer whether people who live in green communities are healthier because they are wealthier and have access to care better health.
The HEAL study was set up with a control group and an intervention, meaning something measurable that some of the participants were exposed to during the study but not before.
Bhatnagar and his team recruited about 750 people who lived in an area 4 miles south of Louisville cut by a highway. The residents were 25 to 75 years old.
Almost 80% were white, and 60% identified as female. Half reported a median household income of $50,000.
The researchers collected blood, urine, nail and hair samples, as well as health data, from each person before starting their intervention.
Then, from 2019 to 2022, they planted nearly 8,500 evergreen trees, 630 deciduous trees — the kind that lose their leaves in the fall — and 45 different types of shrubs in parts of the 4-mile study area, leaving others untouched.
Last year and this year, they took new samples from residents who live in both areas.
People living in the intervention areas had 13% lower levels of high-sensitivity C-reactive protein, a blood marker associated with heart disease, including stroke, coronary artery disease and heart attack. The fall was like starting a regular exercise routine, Bhatnagar said.
“I wouldn’t expect a strong biomarker response, and there may be something really serious here about the impact of trees on health,” said Peter James, director of the Center for Occupational and Environmental Health at the University of California, Davis. School of Medicine, who were not involved in the new research.
How trees can improve physical health
Previous research has shown that spending time in green spaces improves mental health.
The new study showed the link between living among more trees and physical health.
Trees provide shade and cool the areas where they are planted, helping to offset the urban heat effect that disproportionately affects low-income neighborhoods and neighborhoods of color. Hot weather is a major contributor to heart disease and can cause heat stroke in people without pre-existing conditions.
Trees also dampen noise, which has been linked to higher rates of cardiovascular disease, James said.
“They provide areas where people can relax, exercise, and probably more importantly, socialize,” said Joan Casey, an environmental epidemiologist and associate professor of environmental and occupational health sciences at University Washington, in an email.
“They replace other land uses that are harmful to health, like industrial sites,” she said.
Because one of the city’s major highways cuts through the study area, Bhatnagar and his team believe, the trees’ ability to filter air pollution and buffer neighborhoods from breathing in harmful particles could be a key way to reduce tree planting intervention. markers of inflammation. in people who live in green areas.
During the study, the project only planted trees in the parts of South Louisville with the worst air quality. He took air quality samples before the project, and is still analyzing how the new tree cover affected pollution. It’s a tricky business, because air quality varies based on the weather — a windy day can increase or decrease air pollution in some areas, depending on the direction of the wind, and air pollution is worse on days warmer.
The project plans to plant trees in the control group neighborhoods in another three to four years if the intervention neighborhoods continue to show positive results. He also wants to determine whether tree cover improves children’s sleep or immune systems by encouraging outdoor play.
“There is no kind of final proof,” Bhatnagar said. “But this is the strongest evidence of any study ever done on trees and their relationship to health.”
Growing evidence shows the importance of ensuring that green spaces are evenly distributed around cities, which is currently not the case.
Casey said it’s important for city planners to be careful not to create “greenwashing” when they create more equitable access to green spaces in cities — that is, when spaces like waterfronts are restored and housing prices rise for crop, making it unaffordable. for current residents to continue living there when green space is completed.
“The take home message here is that nature is not an amenity; green spaces are not a problem for rich people. They are essential to us as humans,” said James.
This article was originally published on NBCNews.com
