Earth and Health: The Brain Connection

• Environmental factors directly impact brain health, with clean air and water being essential for optimal cognitive function at all ages
• Seniors are particularly vulnerable to environmental toxins, with research showing stronger links between pollution exposure and accelerated cognitive decline
• Active environmental engagement through nature exposure, gardening, and volunteering creates a virtuous cycle that enhances cognitive reserve while benefiting the planet

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Earth Day is upon us again and it’s the perfect time to recognize that caring for our planet isn’t just good for nature—it’s essential for our health, particularly our brain health. The environment we live in directly affects how our brains function, develop, and age, with seniors often being most vulnerable to these impacts. Understanding this connection can motivate us to make choices that protect both our planet and our cognitive wellbeing.

1. Air Quality and Cognitive Function

Poor air quality, resulting from pollution and environmental degradation, has been increasingly linked to cognitive decline and neurological disorders. Research has found that exposure to air pollutants can:

1. Contribute to cognitive decline across all ages and increase the risk of Alzheimer’s disease and other dementias in later life, particularly from exposure to traffic-related pollutants such as nitrogen dioxide, nitrous oxide, black carbon, and particulate matter.
2. Increase risk for dementia and cognitive decline in older adults, with a 2023 systematic review finding that long-term exposure to increased levels of PM2.5 (particulate matter)  and NO2 (Nitrogen dioxide) were most strongly associated with increased dementia risk, while decline in cognitive function, executive function, memory and language were most strongly associated with exposure to PM2.5, PM10 and NO2.
3. Trigger neuroinflammation, oxidative stress, and cerebral vascular damage through multiple pathways, including chronic activation of microglia and astroglia, as documented in this study

For seniors, whose brains may already be experiencing age-related changes, clean air isn’t a luxury—it’s a necessity. A longitudinal study in Neurology (Younan et al., 2020) found that older adults living in areas with improved air quality typically demonstrate better cognitive performance and slower rates of cognitive decline compared to those in polluted environments.

2. The Green Spaces Effect on Brain Health and Stress Reduction

Access to natural environments does more than lift our spirits—it actually changes how our brains function and significantly improves overall health:

• Regular engagement with green spaces has been shown to improve attention, memory, and stress management abilities
• Seniors who spend time in parks, gardens, or forests experience measurable improvements in cognitive function and mental clarity
• Even viewing natural settings through windows or in photographs can provide cognitive benefits and mood enhancement for those with limited mobility

The Japanese practice of “shinrin-yoku” or forest bathing—mindfully immersing oneself in nature using all five senses—has been scientifically proven to provide multiple health benefits:

• Lower cortisol (stress hormone) levels by up to 15% after just 15-20 minutes
• Reduce blood pressure and heart rate, and boosts immune function by increasing natural killer cells that fight disease
• Improve sleep quality, particularly beneficial for seniors who often struggle with sleep disorders

Spending time in nature has also been shown to significantly reduce rumination (repetitive negative thoughts) and activates the parasympathetic nervous system—our “rest and digest” mode—counteracting chronic stress that accelerates cognitive aging. 

For seniors experiencing anxiety, depression, or stress-related cognitive issues, spending at least 120 minutes weekly in nature can significantly improve health and wellbeing, comparable to the effects of some medications but without side effects.

The “biophilia hypothesis” suggests humans have an innate connection to nature that, when nurtured, promotes overall wellbeing. For seniors, cultivating this connection through gardening, nature walks, or simply sitting outdoors can support brain health while simultaneously fostering environmental stewardship.

3. Water and Neurological Health

Dehydration, more common in seniors due to decreased thirst sensation, can rapidly impair cognitive function and exacerbate existing neurological conditions, according to research in the European Journal of Clinical Nutrition (Masento et al., 2014)

Dehydration of just 2% body mass impairs attention, executive function, and motor coordination. Elderly adults—especially women—are at higher risk due to physiological changes that reduce water storage, thirst sensation, and kidney function. 3

When the brain lacks proper hydration, it must work harder to complete the same mental tasks, while performing worse. At the same time, trace amounts of contaminants in drinking water (metals, pesticides, microplastics) can cause neurological impairments through harmful chemical reactions, breaking down cell walls, and neurotransmitter interference. 

This combined threat of inadequate hydration and compromised water quality creates a significant but often overlooked risk to cognitive health. This dual challenge may speed up memory loss and thinking problems in older adults, potentially increasing their risk of developing dementia as they age.

4. Building Cognitive Function Through Environmental Engagement

Environmental engagement and sustainable living practices offer cognitive benefits beyond reduced toxin exposure:

• Research found that gardening activities provide multiple benefits for older adults, with community gardening particularly enhancing social engagement, physical exercise, and self-esteem —all key factors in maintaining cognitive health in seniors. Members of gardening groups reported significantly more social and physical benefits than non-members, supporting the role of nature-based community activities in promoting positive aging
• Intergenerational volunteering programs provide purpose and connection for older adults, with research finding that such activities significantly reduced stress for participants with mild to moderate dementia.
• This ‘use it or lose it’ principle applies to both environmental and cognitive health—active engagement protects and enhances function over time. A 20-year longitudinal study found that environmental volunteering in midlife was significantly associated with improved physical activity, better self-reported health, and fewer depressive symptoms in older adults.

Earth Day reminds us that the health of our environment and our brains are inseparably connected. By making choices that protect clean air, water, and natural spaces, seniors can simultaneously care for their cognitive health and contribute to a healthier planet for future generations. The evidence is clear—when we nurture our environment, we nurture our brains, creating a legacy of health that extends far beyond our individual lives.