As with real estate, location matters when it comes to brain health outcomes [1]. Urban centers can bring opportunities for social engagement which are beneficial for brain health, but they can also lead to higher exposures to pollution and stress, which are associated with greater risk for dementia [2]. In recent years there have been attempts to explore whether urban green spaces, regions covered in vegetation, such as grass and trees, can influence brain health and modify dementia risk.
An epidemiological study in the U.S. found that living in a greener neighborhood was associated with lower odds of developing Alzheimer’s disease [3]. Similar results were found in studies examining the relationship between green space and dementia or cognitive decline in Canada [2] and the UK [4]. Although the relative greenness of an area often varies with socioeconomic status, the protective value associated with green spaces is generally consistent across income levels [2].
While the majority of studies conducted thus far have found modest positive associations between green spaces and brain health-related metrics, some studies did not find these associations [5]. The discrepancies are thought to be related to differences in how the studies were conducted, and critically, in how green spaces were defined. The most commonly used measure of greenness is the Normalized Difference Vegetative Index (NDVI), which uses light to determine how many oxygen-producing plants are in a given region. In the studies described above, the dementia risk decreased as the NDVI of the neighborhood increased. However, this measure does not distinguish between the different types of green spaces, for example, a public park versus a vacant lot.
The results of a study assessing the impact of different types of green spaces suggest that not all green spaces are created equal with respect to dementia prevention [6]. The study, which took place in Australia, found that regions with more tree canopy were associated with a lower incidence of dementia, but a similar association was not seen with open grass regions. No specific type of green space has been conclusively tied to better brain health, but rather, it is thought that the protective effect is related to the way the green spaces are used.
The primary mechanisms by which green spaces are thought to confer benefit to the brain is through the mitigation of air pollution, stress reduction, and the promotion of physical activity and social interactions [5]. Therefore, green spaces that encourage interactions with nature as well as with others via activities, such as hiking or athletics, are expected to confer the greatest benefit. In this way, living near a green space may not be enough; it is also important to actively engage with the green space. Gardening is a great way to experience the brain health benefits of green space engagement, as regular gardening activity is associated with reduced risk for dementia [7; 8].
Studies have found that exposure to green spaces is important throughout the lifespan [5]. Cognitive measures related to attention show the most consistent relationship with green space exposure, suggesting that stress reduction may be the main mediator of the effects on cognition [5]. While green spaces benefit everyone, they may be especially important for city dwellers to combat the negative health consequences of their urban environment. The next time you feel stressed, try spending time in your local green space, and your brain will thank you.
Betsy Mills, PhD, is a member of the ADDF's Aging and Alzheimer's Prevention program. She critically evaluates the scientific evidence regarding prospective therapies to promote brain health and/or prevent Alzheimer's disease, and contributes to CognitiveVitality.org. Dr. Mills came to the ADDF from the University of Michigan, where she served as the grant writing manager for a clinical laboratory specializing in neuroautoimmune diseases. She also completed a Postdoctoral fellowship at the University of Michigan, where she worked to uncover genes that could promote retina regeneration. She earned her doctorate in neuroscience at Johns Hopkins University School of Medicine, where she studied the role of glial cells in the optic nerve, and their contribution to neurodegeneration in glaucoma. She obtained her bachelor's degree in biology from the College of the Holy Cross. Dr. Mills has a strong passion for community outreach, and has served as program presenter with the Michigan Great Lakes Chapter of the Alzheimer's Association to promote dementia awareness.
Get the latest brain health news:
Can the way we breathe affect brain health?
How does light exposure affect memory?
Does cognitive and social activity reduce the risk of dementia?
Do loud noises harm the brain?
Targeting 12 risk factors throughout life may delay or prevent up to 40% of dementia cases
Is cognitive function affected by hot weather?
Loneliness in the Time of Covid-19
Can dehydration impair cognitive function?
Loneliness and the Risk of Dementia
Cognitive and Physical Activity Reduce Your Risk for Dementia
Does Stress Worsen Cognitive Functions?
Danger in the Air: Does Pollution Raise Your Dementia Risk?