Climate change is often viewed as a symptom of the worsening health of the planet, but it can also influence the health outcomes of everyone living on the planet. In addition to altering the environmental landscape, climate change impacts the function of our brains in ways that make us more vulnerable to neurological injury and cognitive decline.
Heat stress: Brain activity is highly sensitive to changes in temperature [1]. As a very metabolically active organ, the brain tends to be slightly hotter than the rest of the body, and it relies on this temperature differential to cool down [2]. Our core body temperature changes by a few degrees over the course of the day, such that it is warmer during the day and cooler at night. As the body cools down, there is an increase in the flow of blood to the brain, which is critical for removing both the metabolic waste products and heat that build up in the brain throughout the day. Sustained exposure to a hot environment can prevent the body from entering its cooling period. Disruption of this rhythm in body temperature puts the brain at risk of overheating.
Heat stroke occurs when the core body temperature reaches 104oF (40oC) [3]. When the body gets this hot it can no longer cool the brain, which can cause it to shut down, resulting in confusion, fainting, seizures, or even death. However, heat-related damage to the brain is also possible at temperatures below this threshold.
As the temperature increases, brain cells can become overactive, which increases the risk for seizures [4]. Heat also increases the potential for blood clots, resulting in a heightened risk for strokes during heat waves [5]. Dehydration makes blood thicker, and high temperatures disrupt the function of blood cells involved in the clotting process. Under heat stress, cellular activity may be limited to only the most basic functions. Prolonged exposure to high temperatures may promote the accumulation of misfolded proteins associated with neurodegenerative disease due to a reduction in brain cell maintenance [6].
Hot nights are especially dangerous to brain health, since this is the time when the brain experiences its required cooling off period [5]. In addition to the risks described above, the inability of the body to effectively cool down at night also disrupts sleep [7], a critical process for keeping the brain healthy.
Those with dementia are at heightened risk for the negative impacts of heat [8]. They are generally unable to cool down as effectively due to difficulties in recognizing that they are overheated and taking the necessary steps to protect themselves from the heat. The bodily temperature rhythm is also blunted in these individuals [9], which can further increase the risk for heat-related brain injury.
Environmental toxins: Hotter air and water temperatures can increase our exposure to pollutants and pathogens. Exposure to environmental toxins, such as air pollution, heavy metals, and pesticides is associated with increased risk of neurodegenerative disease [4]. Warmer temperatures increase the production of ozone and the level of dangerous particulate matter, resulting in worse air quality [10].
Increased runoff of stormwater and fertilizers full of pollutants and nutrients combined with warmer water temperatures trigger harmful algal blooms [9]. These blooms can disrupt aquatic ecosystems and release neurotoxins into the environment. These toxins can make our way into our bodies by consuming contaminated seafood and plants irrigated with contaminated water.
We can also become exposed to neurotoxic pathogens, such as the brain-eating amoeba, Naegleria fowleri, by swimming in contaminated lakes and rivers [11].
Stress: Chronic stress makes us more vulnerable to a wide array of age-related diseases, including dementia. Climate change is associated with the increased intensity of natural disasters, such as hurricanes, floods, and wildfires, which can result in the loss of life and property. Displacement from these events can have lasting effects, such as upending livelihoods and disconnection from support networks. These traumatic life events can also trigger stress disorders [11]. All of these things can decrease the resiliency of our brain and body to cope with future stressors.
What you can do:
Although we cannot stop climate change on our own, by taking these steps, we can help protect ourselves from the negative health effects stemming from it.
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.
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