Rachel Keith, associate professor at the University of Louisville School of Medicine, said researchers planted more than 6,000 mature trees, shrubs and grasses of different species in an experimental urban park located in the city. Their data show participants who live near the park had reduced inflammation – measured by a biomarker in the blood – after the planting.
Keith pointed out that inflammation is a key risk factor for developing chronic disease.
"When we looked at people before and after planting, only the people who lived in the area that had trees had a reduction in this really significant marker for health," Keith noted.
Evidence also suggests that increased biodiversity in green areas can contribute to better health. A report from the Center for American Progress found 70% of low-income communities nationwide lack access to natural, forested areas.
According to National Recreation and Park Association data, 58% of American adults spend more than 30 minutes a day outside. Gen Xers are more likely to spend time outdoors, while Gen Z adults are more likely to stay indoors. Keith added that living in close proximity to green spaces and cleaner air also affects sleep quality.
"We did a sleep study as part of a sub-study that showed the cleaner the air is in the place where you're sleeping, the better your sleep quality," Keith emphasized.
The majority of low-income city blocks in the U.S. have few trees and higher average temperatures than higher-income neighborhoods, according to research from the Conservation Law Foundation.