The first heat wave of this summer has put 8 out of 10 Spanish municipalities at risk for health. Although the effect of dehydration on the body is the main concern, the brain also suffers from this upward trend in temperatures, which during the past year —the third warmest on record— temperatures reached a high of 46.8 degrees at Valencia airport and 44 degrees at Bilbao airport. Recent studies have shown that excessive heat reduces cognitive abilities, both for studying and working. Furthermore, while the brain works overtime to keep the body cool, extreme temperatures increase aggression and stress, and particularly affect patients with certain psychiatric disorders.

The brain is a temperature-sensitive organ that is not prepared to work at 45 degrees, and in that case cognitive function slows down, explains Sandra Giménez, a clinical neurophysiologist at the Hospital de la Santa Creu i Sant Pau in Barcelona: “Extreme heat affects "It affects all the cognitive functions of the brain: our ability to react, our ability to respond, memory, etc. Everything takes a lot more time, we go much slower. We're not going to say that neurons melt, but there is an effect, performance is much worse with high temperatures."

 

The scientific evidence supports this. Taking an exam on a day when it is hotter than 32 degrees results in a 14% reduction in grades compared to taking the same exam at 22 degrees and reduces the chances of passing a subject by almost 11%, according to a study in New York City public schools in 2018. “I estimate that over the period 1998 to 2011, more than 510,000 exams that would otherwise have been passed were failed due to high temperatures, affecting at least 90,000 students, possibly many more,” concludes Jisung Park, a professor at the Harvard Kennedy School and author of the study.

Other investigation, also conducted in the US, noted that “the learning rate declines with an increase in the number of hot school days.” And another study, which compared the performance of Boston University students during a 2016 heat wave, found that those living in non-air-conditioned rooms (at an average temperature of 27 degrees) were 13% slower in reaction time on arithmetic tests and got almost 10% fewer correct answers per minute than their air-conditioned peers (at 22 degrees).

And although most of the studies have been carried out in academic settings, the cognitive impairment caused by heat also affects the workplace: an investigation carried out in 2006 found that the highest productivity was achieved at a temperature of around 22 degrees. At eight degrees higher, the yield was reduced by almost 9%.

“There are numerous studies that establish links with mental health, mood and brain behavior in the heat, so people with mental health problems are especially vulnerable,” says meteorologist and science communicator Mar Gómez. The author of Weather-sensitive: how the weather affects our physical and mental health (Peninsula), points out that there is research showing that higher temperatures decrease positive emotions such as joy or happiness, and increase negative ones such as anger or stress.

More aggression and worse mental health

“We know that people with schizophrenia can experience difficulties with regulating body temperature and that changes in temperature can alter the symptoms of mood disorders. Some psychiatric medications, including certain antidepressants and antipsychotics, can also affect the way the body regulates temperature, and people who take them are especially vulnerable to the effects of extreme heat,” explains Gomez.

Among the negative emotions associated with heat, anger is one of the most studied, as are two of its direct consequences: aggression and violence. “Extreme heat can increase irritability and decrease self-control, which can translate into more aggressive behavior. The relationship between intense heat and aggression is real,” says Valentín Martínez, a doctor in Psychology from the Complutense University of Madrid and member of the College of Psychology of Madrid.

A study published in 2022 in The Lancet A study that analyzed four billion tweets concluded that very high or very low temperatures aggravate aggressive online tendencies and increase hate speech. The increase in this type of tweets was 22% on days with extremely hot temperatures (42 to 45 degrees). Another study found a direct linear increase in car horn use with increasing temperature. And there is even studies who concluded that each degree of increase in annual temperatures would be associated with an average increase of almost 6% in the number of homicides.

An investigation The study, led by experts in gender violence, by specialists in epidemiology and by psychologists from the Police and Civil Guard, analysed the months from May to September in the period 2008-2016 in the Community of Madrid and came to the conclusion that for every degree by which the maximum daily temperature exceeds the threshold of 34 degrees, the number of feminicides within couples increases by 28.8% compared to the average. “This does not mean that the study of the Community of Madrid revealed that gender violence is a direct consequence of the heat. Far from it. Its conclusion was that the heat is a factor that influences the increase in violence, together with other causes,” Mar Gómez clarifies. An opinion that is corroborated by Sandra Giménez, who believes that high temperatures can cause anyone to be more aggressive: “It does not mean that we are all going to stab someone. There has to be a psychopathological basis.”

This is how heat impacts the brain

The explanation for all these consequences, according to Valentín Martínez, could be found in the fact that "the heat forces the brain to work harder to regulate body temperature, which negatively affects mental capacity,” since the brain devotes much of its resources to keeping the body cool.

“We have to know that our brain works properly thanks, among other things, to the hypothalamus, which is the coordinator of the autonomic nervous system and acts as a kind of internal thermometer of the brain. When it detects that there are changes between its own temperature and that of the skin thermoreceptors, the hypothalamus establishes the mechanisms to regulate it,” explains Mar Gómez. These mechanisms are sweating, vasodilation or the production of adrenaline. And according to the expert, precisely this production of adrenaline “is one of the causes of greater irritability when we go through periods of intense heat.”

In addition to this overexertion of the brain, there is another extremely important factor: sleep. “On tropical nights, when the ambient temperature does not fall below 20 degrees, our brain becomes overexcited and body sweating increases, so that our body is in a state similar to that of having to perform intense physical activity, which is totally incompatible with rest or with comfortably maintaining sleep,” says the meteorologist. “It is a fish that bites its tail,” adds Sandra Giménez, coordinator of the Cognition and Sleep working group of the Spanish Sleep Society (SES). According to this expert, excessive heat causes a kind of vicious circle. We sleep worse, which makes us cognitively slower, more anxious and more irritable; and then the heat during the day accentuates these symptoms. “Control is lost at the prefrontal level of the brain and the brake on the amygdala, which is the area where we have emotions, decreases, so that everything negative is magnified,” she says.

There are no magic potions to counteract these effects. The advice, says Martínez, is common sense: stay well hydrated and drink enough water, avoid prolonged exposure to extreme heat, especially during the central hours of the day, look for cool places with air conditioning, wear light and light-colored clothing to facilitate perspiration, limit intense physical activity outdoors during the hottest hours, eat fresh, light and water-rich foods such as fruits and vegetables. And do everything possible to get enough rest.

 

Source: https://elpais.com/salud-y-bienestar/2024-07-23/neuronas-melt-down-as-high-temperatures-are-lastran-at-the-brain’s-function.html