Could living in a tree-filled neighbourhood help reduce your risk of heart disease?

You might be thinking. “No way!”

But that’s exactly what initial findings from the US Green Heart Louisville Project HEAL study have shown. The study is seeking to show whether planting trees to reduce air pollution can decrease specific health risks including heart disease, encourage more outdoor participation and encourage a ‘GREENPRINT for healthier cities.’

Louisville’s air quality ranks amongst the worst in the State of Kentucky and the city has high rates of heart disease. The current tree canopy is 37% and declining at the rate of 54,000 trees per year.

For the study, in 2018, 750 Louisville residents were recruited, aged between 25-75 years and living in a 4-mile area. They had baseline samples of blood, urine hair and nails taken. Then between 2019 and 2022, 8,500 evergreen trees, 630 deciduous trees and 45 types of shrubs were planted in specific parts of the study area, i.e. those areas identified with the worst air quality, leaving other areas bare.

Further test samples were repeated after one year and two years. The researchers found that the people who lived in those neighbourhoods that had twice as many trees and shrubs than others, had 13% lower levels of the inflammatory blood marker high-sensitive C-reactive protein (hsCRP).

What does this mean? 

The significance of this is that higher levels of this marker are associated with an increased risk of heart disease, including heart attack, coronary artery disease and stroke, type two diabetes and some kinds of cancers.

The drop in hsCRP was similar to that shown when individuals start a regular exercise routine.

How this works is not fully understood. However, it is known that trees act as effective air purifiers removing pollutants and improving air quality, which could be associated with the reduction in general inflammation

The plan now is to plant more trees in the control area in 3-4 years’ time, if the results of the intervention continue to be found to be positive.

This is a helpful study supporting evidence that good urban design with sufficient tree cover and greenery is important to human health and well-being. The study is set to complete in 2026 by which time it is hoped it will be possible to determine how changing neighbourhood characteristics such as green space, affect heart health, risk factors for other diseases and a sense of well-being or neighbourhood cohesion.

Watch this space!