Green Heart Louisville Project

The Green Heart Louisville Project is a groundbreaking scientific study that is testing the hypothesis that introducing more green trees and shrubs into a neighborhood can directly lower the risk of cardiovascular disease (CVD), the leading cause of death worldwide.

Launched in 2018, the study investigates whether and how living among more densely greened surroundings contributes to better heart health. The design of the study closely mirrors clinical trials, which test whether medical treatments are eUective. The Green Heart team applied the treatment—the addition of thousands of large trees and shrubs—to the center of a four-square-mile area in south Louisville. Trees and shrubs were not planted in the areas surrounding the central planting area, known as the control area. Researchers then compared the health of residents to determine whether the plantings had any impact on their health.

First Clinical Outcomes

In August of 2024, the Green Heart Louisville team announced the first clinical outcomes from the study. Initial findings indicate that people living in neighborhoods where the number of trees and shrubs was more than doubled showed lower levels of a blood marker of inflammation than those living in the control area. General inflammation is an important risk indicator for heart disease and other chronic diseases.

Those living in the greened area had 13-20% lower levels of a biomarker of general inflammation, a measure called high-sensitivity C-reactive protein (hsCRP), compared to those living in the areas that did not receive any new trees or 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 of hsCRP by this percentage corresponds to nearly 10-15% reduction in the risk of heart attacks, cancer, or dying from any disease.

Global Impact

The Green Heart Project’s work to establish a scientific link between nature—specifically urban greenery—and human health is already influencing projects worldwide. The first clinical outcomes announcement garnered widespread national media attention, including a segment on the “TODAY Show”. Many research papers, posters and talks on the project have been delivered to both scientists and laypeople since the project’s inception with additional research and outreach to come in the years ahead.