It’s no secret that humans are physically and spiritually connected to nature. Whether it’s the gentle touch of a warm breeze, the familiar sound of rustling leaves, or the scent of freshly cut grass, nature taps into our primal instincts, effectively calming our bodies and minds.

An increasing body of research is helping measure what most people inherently know. Nature is good for us. As modern technology draws us indoors, the critical need to reconnect with green spaces is more pressing than ever.

Recent Data on Green Spaces and Cardiovascular Outcomes

Stroke rates have steadily risen over the past 3 decades.¹ Today, strokes represent the second leading cause of death and the third leading cause of disability worldwide.

Known risk factors include exposure to the following:

• Air pollution
• High-traffic roadways
• Hot or cold temperatures

Conversely, green spaces are associated with a lower risk for stroke and other cardiovascular diseases, having the potential to significantly impact public health on a global scale.

A meta-analysis and systematic review examined data from 53 studies spanning 18 countries, including over 100 million people.² The investigators calculated the normalized difference vegetative index (NDVI) to quantify the greenness of the participants’ local environment. After conducting publication bias tests, they found “strong and robust evidence for the beneficial effects of green space exposure on cardiovascular health.” Specifically, every 0.1 unit increase in NDVI was associated with a 2 to 3% reduction in death from cardiovascular disease, ischemic heart disease, and cerebrovascular disease. The same reduction was also observed regarding the incidence and prevalence of stroke.

Similar effects were seen during a 5-year study in Florida.³ This study found that 229,034 Medicare beneficiaries consistently exposed to “high greenness” had a 9% lower incidence of new cardiovascular diseases than those in “low greenness.” Conditions measured in the study included acute myocardial infarction, atrial fibrillation, heart failure, ischemic heart disease, hypertension, and stroke. While this study doesn’t tell us much about those with existing heart problems, it emphasizes the preventative potential of green spaces.

Cardiologists can help raise their patients’ awareness about the heart health benefits of nature and explore safe ways to access green spaces.

Measuring the Restorative Effects of Nature

Despite positive findings, nature’s health-promoting properties remain somewhat of a mystery. Some theories on the magic behind green spaces include:

• Cooling effects from shading by trees
• Exposure to diverse microorganisms
• Promotion of physical activity
• Opportunities for social interaction
• Reduction of noise and air pollution

Given the established links between mental health and heart health, it’s no surprise that natural environments benefit multiple body systems and help ward off various illnesses. Studies show that walking in nature helps calm neuronal activity in the subgenual prefrontal cortex. This effect promotes a sense of well-being, and the practice has been coined as “forest therapy” or “forest bathing” by different cultures.¹

In another meta-analysis, green spaces were linked to lower salivary cortisol levels and reductions in heart rate, diastolic blood pressure, and type 2 diabetes.¹ Whether nature improves heart health directly or indirectly through its influence on metabolism, stress, or another route becomes less relevant given the magnitude of cardiovascular disease in society and the desperate need for a multipronged approach to alleviate its burdens.

Research also suggests that certain types of green spaces are more impactful than others. For example, forests and tree canopies are more strongly linked to cardiovascular and respiratory benefits than grassland.⁴ Proposed theories on this observation are that trees offer shade and may enable more daily activity in hot climates. Perhaps people are more likely to walk and bike vs relying on cars when shielded from the sun by leaves and branches. It’s also possible that foliage helps filter common health hazards, like environmental pollution and noise, promoting better health as an ongoing effect in the background.

What This Means for Clinical Practice and Communities

There’s good evidence that green spaces are protective against cardiovascular diseases and promote favorable post-stroke outcomes.¹ These findings are relatively consistent in both suburban and urban settings. However, parks and natural spaces in urban areas must be well-maintained and kept safe for residents to benefit from them.⁵ It is important to make green spaces welcoming for families and elderly residents who rely on these shared spaces.

Cardiologists can help raise their patients’ awareness about the heart health benefits of nature and explore safe ways to access green spaces. Some ideas may include the following:

• Creating walking, hiking, or biking groups
• Organizing recurring park clean-up days
• Posting community rules for parks and trails
• Promoting the use of community gardens
• Researching transportation to natural environments beyond the city

Encouraging patients to develop solutions that work for their community can empower and foster positive changes in situations where green spaces are harder to come by.

Project Learning Tree is one of several initiatives that are bringing more green spaces to urban areas.⁶ The program is based on the Miyawaki method developed in Japan during the 1950s. First, a small patch of land is selected, and gardeners research the native local tree species. Next, the soil is prepped for planting a large number of seedlings in a small space. Community members support their growth with weeding and watering. These initial efforts can get mini forests up and running much faster than naturally occurring forests — in some cases, as quickly as one-tenth the time it takes a forest to grow on its own.

Several states have used Project Learning Tree to help adults and students in urban communities “greenify” their cities. Stories of growing fresh produce on small strips of land in food deserts and transforming unused parking lots into green spaces can be found on their website. Sometimes, these efforts are met with resistance from local government and zoning regulations, but emphasizing the implications for public health can help drive solutions.

The Environmental Protection Agency also offers various resources promoting the benefits of green infrastructure.⁷ Integrating trees, shrubs, and other plants into the planning for buildings and roadways helps make these areas more desirable and improves the quality of life for those who use them. Additionally, plants help filter stormwater, support wildlife, and reduce flooding. With so many potential benefits, efforts to increase green spaces must be a priority for patients, providers, and communities of all types.

References:

1. Whyte M, Douwes J, Ranta A. Green space and stroke: a scoping review of the evidence. J Neurol Sci. Published online January 7, 2024. doi: 10.1016/j.jns.2024.122870
2. Liu XX, Ma XL, Huang WZ, et al. Green space and cardiovascular disease: a systematic review with meta-analysis. Environ Pollut. Published online February 15, 2022. doi: 10.1016/j.envpol.2022.118990
3. Brown SC, Aitken WW, Lombard J, et al. Longitudinal impacts of high versus low greenness on cardiovascular disease conditions. JAHA. Published online September 30, 2024. doi: 10.1161/JAHA.123.029939
4. Nguyen PY, Astell-Burt T, Rahimi-Ardabili H, Feng X. Green space quality and health: a systematic review. Int J Environ Res Public Health. Published online October 20, 2021. doi: 10.3390/ijerph182111028
5. Kim K, Joyce BT, Zheng Y, et al. Associations of urban blue and green spaces with coronary artery calcification in black individuals and disadvantaged neighborhoods. Circulation. Published online June 27, 2024. doi: 10.1161/CIRCULATIONAHA.123.067992
6. Reynandez R. Innovative ways to create more urban green spaces. Project Learning Tree. Accessed December 30, 2024.
   https://www.plt.org/
7. Benefits of green infrastructure. United States Environmental Protection Agency. Published August 27, 2024. Accessed December 30, 2024.
   https://www.epa.gov/green-infrastructure/benefits-green-infrastructure