Heat has an effect on brain function. A new 12-year-long American study found a connection between heat waves and a decrease in brain function, especially among adults. The findings were published in the Journal of Epidemiology and Community Health.
The researchers who published their findings tried to understand the relationship between exposure to extreme heat and cognitive decline. They analyzed data from nearly 9,500 US adults age 52 and older surveyed over a 12-year period, starting in 2006, as part of the University of Michigan Institute for Social Research's Health and Retirement Study, which measures subjects' cognitive functioning over time.
The researchers also looked at socioeconomic indicators of the neighborhoods where the participants lived. In addition, they calculated the subjects' cumulative exposure to extreme heat (the number of days the heat index reached or exceeded a certain threshold while specifying the location where the test was performed) during this 12-year period, based on historical temperature data from the Centers for Disease Control's National Public Health Environmental Tracking.
High exposure to extreme heat is associated with faster cognitive decline among residents of poor neighborhoods, but not for those who live in richer neighborhoods, apparently because populations with a high socioeconomic level regulate the temperature through air conditioning in their home, workplace and car.
"Cognitive decline may not manifest immediately after a single heat event, but repeated or prolonged exposures to extreme heat may be harmful," explained Professor Virginia Chang, from the NYU School of Global Public Health and leader of the research team. "Cumulative exposure to extreme heat may trigger a chain of brain reactions including cellular damage, inflammation and oxidative stress, all of which may eliminate a person's cognitive reserve."
"Affluent neighborhoods have resources that can help in a heat wave - things like well-maintained green spaces, air conditioning and cooling centers," said Professor Hannah Lee, a sociologist from Sungkyunkwan University in Seoul, who participated on the research team. "In disadvantaged neighborhoods, these resources may not exist. Other factors associated with disadvantaged neighborhoods – residents who experience chronic stress, greater social isolation and fewer specialized services for cognitive health - can also contribute to this gap."
The researchers call on local governments and health officials to develop policies and tools that identify residents who are sensitive to extreme heat, empower communities at risk, map their specific needs and develop targeted support and increased communication with these populations.
"Heat waves may have several mechanisms of damage to the brain," explains Dr. Ophir Keret, neurology specialist and director of the Dementia Clinic at Beilinson – Rabin Medical Center. "When the temperature is high, we sleep less well, and various mechanisms in the body are damaged, such as the hormonal system and the functioning of various structures in the brain.
"What is interesting about the study is the researchers' follow-up of the volunteers for 12 years. Now the question is what is the exact mechanism that caused the brain damage, and it is assumed that there are several reasons that lead to the damage, which we will only discover in further subsequent studies."
"It has been known in the medical literature for years that extreme heat increases the risk of cognitive impairment and stroke, and there may also be a mechanism of Alzheimer's observed in studies on laboratory animals," says Professor David Tanne, director of the Stroke and Cognition Institute at Rambam and chairman of the Israel Neurological Association. " There is no reason to panic, and more studies are needed, but it has long been clear that everything should be done to avoid exposure to extreme heat, not only because of possible heatstroke and dehydration, but also because of the long-term effects.
"I recommend people to be in cool places, turn on the air conditioner as needed, the governments should do everything possible to increase the shading and vegetation that significantly lowers the temperature. And for all of us, do everything to protect the planet," he asserted.