Extreme Heat Impacts the Brain and Increases Risks for Some Individuals

Extreme Heat Impacts the Brain and Increases Risks for Some Individuals

The Impact of Heat Waves on Cognitive Decline in Older Adults

Heat waves are becoming more frequent and intense due to global warming. According to a study, 2023 is predicted to be the hottest year on record. While we are already aware of the physical health risks associated with extreme heat, a new study suggests that there may be another consequence: faster declines in older adults’ memory and thinking skills.

The study, conducted in the United States, examined nearly 9,500 older adults over a 12-year period. It found that those with greater exposure to heat waves experienced a steeper decline in cognitive function. Cognitive function refers to critical mental skills such as memory, reasoning, and judgment.

Of particular concern, the connection between heat and cognitive decline was especially evident among older Black Americans and those living in poorer neighborhoods. These groups typically have fewer resources to protect themselves from the scorching summer heat. However, it’s important to note that the study only shows an association between heat and cognitive decline and cannot solely blame temperature extremes for the decline.

Lead researcher Eunyoung Choi, a postdoctoral associate at NYU School of Global Public Health, highlights the complexity of cognitive decline, which is influenced by numerous factors. Isolating the specific effect of extreme heat from these complex factors is a challenging task. Nonetheless, repeated exposure to heat waves can have various direct and indirect effects on older adults’ mental acuity.

Extreme heat has short-term effects on mental performance, often leading to a dulling of cognitive abilities. Moreover, continued exposure over time may promote inflammation and damage brain cells. Additionally, sizzling temperatures can indirectly impact cognitive decline through their effects on heart health. Conditions such as high blood pressure, diabetes, and heart disease, which are associated with cognitive impairment, may be exacerbated by extreme heat.

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Furthermore, oppressive heat can also interfere with sleep and limit the ability to engage in exercise or social activities – all of which are essential for maintaining cognitive function in older adults. This reduced engagement can take a toll on their cognitive abilities and contribute to cognitive decline over time.

Interestingly, the study found that low-income individuals and Black Americans may be more vulnerable to the effects of extreme heat on cognitive decline. Choi suggests that the concept of “cognitive reserve” may play a role. Cognitive reserve refers to the brain’s capacity to adapt and preserve function as age or disease begins to change the brain tissue itself. Individuals who are disadvantaged, facing chronic stress and limited educational and work opportunities, may start with a lower cognitive reserve. Consequently, their cognitive reserve may erode faster over time, making them more vulnerable to additional stressors like extreme heat.

Kristina Dahl, a principal climate scientist with the nonprofit Union of Concerned Scientists, finds the study thought-provoking. She notes that while scientists have some knowledge about the acute effects of extreme heat on cognition, this study is one of few exploring the cumulative impact of heat exposure on longer-term cognitive decline. However, she and Choi both caution that it is challenging to disentangle the effects of extreme heat from other factors in people’s lives. To gain a better understanding, more studies are needed.

The findings of this research, recently published in the Journal of Epidemiology and Community Health, were derived from a cohort of 9,448 U.S. adults aged 50 and older who underwent cognitive tests repeatedly over a 12-year period. Using temperature data from a government database, the researchers estimated participants’ long-term exposure to heat waves.

Interestingly, the study did not find a direct relationship between heat exposure and participants’ cognitive scores at the beginning of the study. However, when examining the trajectories over time, the researchers discovered that high exposure to extreme heat was associated with a faster decline in cognitive scores – particularly among Black older adults and individuals living in disadvantaged neighborhoods.

Among Black participants, those with high exposure to extreme heat were projected to experience a 42% decline in cognitive scores between the ages of 65 and 85, compared to a 32% decrease among Black adults with less heat exposure. Similarly, individuals in poorer neighborhoods with high heat exposure had a projected decline of 37%, compared to 29% among low-income people with less heat exposure.

Considering the implications of this study, Dahl emphasizes the importance of protecting vulnerable Americans from extreme heat. Measures such as ensuring easy access to cooling centers in low-income areas, preventing utility shut-offs due to unpaid bills, and providing sufficient shade, water, and rest for outdoor workers are critical in mitigating the impact of extreme heat on cognitive decline.

In conclusion, this study sheds light on the potential cognitive consequences of heat waves, particularly among older adults. While more research is needed to fully understand the relationship between extreme heat and cognitive decline, it is crucial to take proactive measures to protect vulnerable populations from the detrimental effects of extreme heat. By prioritizing access to cooling centers and implementing supportive measures, we can safeguard older adults’ cognitive health and overall well-being.