The Effects of Extreme Heat on the Brain |
The brain is negatively affected by environmental heat, even at current levels.
Frontal lobe changes from heat can impede planning, decision-making, and attention.
Cognitive test scores fall as temperatures rise, affecting memory and reaction time.
Although the large majority of climate scientists hold firmly to the belief that the climate is heating up at an unsustainable rate, an undetermined segment of the population is convinced that global warming worries are overblown—a belief that runs counter to demonstrable scientific evidence, as well as everyday observation.
In 1988, experts testified before Congress in the first congressional hearing about climate change. Every year in the 21st century has been hotter than 1988, with each decade hotter than the previous. The last three years, from 2023 to 2025, were the hottest in recorded history, dating from 1850, when sufficient direct measurements by instruments (thermometers) allowed an estimate of temperature. The last 11 years have included all of the warmest years observed using instrumental methods.
But one does not have to look at extreme temperature elevations to encounter convincing evidence that even less extreme examples affect the smooth operation of the human brain. If we stick to temperatures we’ve already experienced, especially in 2023, 2024, and 2025, there is more than enough to worry about.
The Effect of Heat on the Brain
In general, even moderate heat elevation adversely affects the brain’s reasoning power and thought patterns. As the temperature and duration of the heat wave increase, the brain’s neurotransmitters suffer disruptions in their messaging of the signal from one neuron to the next. In reaction, the receiving neurons may fire too rapidly, too slowly, slightly erratically—it doesn’t matter which; the results are disruptive effects on mood, memory, thinking, and sleep. Added to that is the loss of electrolytes due to sweating—leading to weakness, muscle cramps, and in some cases seizures. Additional heat exposure affects perception and behavior, especially clear thinking, sustained attention, memory, and rapid decision-making.
Perhaps most striking of all are the subjective mental experiences. Think back to the last time you were ensnared in a “heat wave,” even one of moderate intensity by today’s standards (90-100 degrees Fahrenheit). You were undoubtedly totally preoccupied with your discomfort; you could hardly think of anything else. In response to your heat-induced lethargy and restlessness, your concentration was almost nil, and you couldn’t “think straight—a colloquial phrase for loss of clarity and precision.
Under such conditions, productivity plummeted as you became preoccupied with thoughts of somehow shifting to an air-conditioned environment. If the humidity was also elevated (responsible for the “feels-like” description on the weather reports), the effect on cognition was even greater.
If the temperature reaches triple digits, a person may experience some of the early symptoms of “heat stroke.” But let’s not go there. Let’s stick to problems we can expect from temperatures that the majority of us have already encountered and will surely encounter again.
Heat and Frontal Lobe Changes
A sizable portion of heat-induced brain changes result from heat’s effect on the frontal lobes, located at the farthest front of the brain. The frontal lobes are responsible for, among other things:
Sequencing (keeping bits of information in order).
Executive control (planning combined with anticipation of the consequences of our behavior).
Self-analysis (the ability to imaginatively project ourselves into the future, dating from our current actions in the present moment).
Disorders of the frontal lobes lead to planning difficulties, poor decision-making, difficulty changing one’s mind, distractibility, and impulsivity.
Examples of the consequences of heat-induced frontal lobe failures of thought and judgment include near mishaps, such as turning one’s car precipitously in front of an oncoming driver in a “failure to yield” infraction that can result in an accident. Under cooler conditions, the driver would have stopped and made the turn only after the other car passed by.
Whatever the specific examples, the operating principle remains the same: The quality of our thinking is perpetually at the mercy of temperature. Test-taking provides a proxy for the effects of heat on cognitive function. Scores on cognitive tests plummet in tandem with temperature increases: A 4-degree increase—experienced by the test-taker as only mildly uncomfortable—leads to a 10% decrease in performance on tests of memory, reaction time, and judgment. Other research found a .3% drop for every 1 degree increase in temperature above 72 degrees. Overall, the hotter the average daily temperature during a typical school year, the worse students perform on standardized tests.
But it’s not only the quality of our thinking that is affected, but our ability to control our tempers as well. Decades of research have established that as temperatures rise, so too do riots, domestic violence, and aggravated assaults.
Among less serious consequences, experiments have shown that at higher temperatures, heat-oppressed drivers telegraph their mounting anger by leaning on their car horns. When this ear-splitting cacophony reaches a certain intensity, many of the so far non-participating drivers respond in kind by honking their own horns.
When experts attempt to characterize the cause of violence, socioeconomic, geographic, and racial inequities are quickly listed, but temperature increases are given scant attention. For example, the U.S. Surgeon’s General 2024 Report “Firearm Violence: a public health crisis in America” doesn’t even mention global warming or heat waves as a precipitant of violence.
Coping With Heat Waves
But explaining heat waves is not nearly as important as responding to them. If heat records continue to occur similar to the pattern of 2023-2025, special precautions will be necessary. The most common, of course, are air conditioning and the intake of adequate amounts of cooling beverages.
New on the scene are portable cooling fans. Perhaps you’ve seen them at lounges and nightclubs. Although these devices may make the wearer feel cooler in both the literal and metaphorical sense of the term, the degree of heat relief offered is strictly limited, as with fans of any size. Much more effective are cooling devices involving direct contact of chilled liquids with the skin.
Such devices were first used in Afghanistan and Iraq with combat troops outfitted with freezing packs placed at strategic places beneath body protective equipment. Further tinkering with the concept resulted in “plastic plates” that fit the contours of the human body. In the 2027 Formula 1 season, drivers will be required to wear such “cooling vests” or icepacks. Similar products are already on the market for general use.
All of which raises a pivotal question: If some of us are already seeking portable body coolers during grudgingly “bearable” temperatures, where will we turn if the naysayers turn out to be wrong (as I suspect they will) and temperatures continue to soar?
This is not an unlikely event, according to the Canadian Center for Climate Modeling and Analysis (CCCma): “2026 will likely be among the four hottest years on record, comparable to 2023 and 2025, and approaching 2024, the hottest year ever recorded.”
It’s now March—only 6 months or so until we know who is right, the climatologists or the nay-sayers. With reluctance and, I must admit, a sense of foreboding, I know where I would now place my bet were I a wagering person.
Richard M. Restak, M.D.
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