It is important to know the risks of heat stroke and to take them seriously. Not only does heatstroke carry a relatively high mortality rate, but those who recover from it are still likely to face future health problemssaid Orlando Laitano, assistant professor of applied physiology and kinesiology at the University of Florida. “We now believe that heat stroke is almost like a concussion.”
In a recent studyLaitano and his colleagues found that heatstroke in mice could alter the genome and create greater susceptibility to future heat and immune diseases.
Currently, about 30 percent of the human population is exposed to hazardous ambient heat for at least 20 days each year. according to a recent study. This figure could rise to 74 percent of the world’s population by 2100 if anthropogenic climate change continues unabated.
“In the face of global warming and climate change, this is becoming — no pun intended — a hot topic,” said Laitano, co-author of a book on the subject. recent review on heat stroke.
Understanding heatstroke and heat-related illnesses
Anyone can develop heat-related illness, including older people and young children. particularly vulnerable. High humidity, strenuous physical activity and consecutive sultry nights also increase our risk.
Heat illness can range in severity from mild heat exhaustion to life-threatening heat stroke. Heat exhaustion is more common and may involve symptoms such as dizziness, fatigue, nausea or headache, but not a dramatic increase in body temperature.
Heat stroke is generally defined as a core body temperature above 104 or 105 degrees Fahrenheit, which causes severe central nervous system dysfunction, including confusion, dizziness and loss of consciousness, and can lead to multiple organ damage, etc.
However, there can be significant differences in individual heat tolerance and some people collapse below that threshold, Laitano said.
Another potential challenge is that heat-related illnesses can distort judgment and the affected person may be unaware that they are in trouble.
How our brain coordinates temperature regulation
Our body’s cells only function properly within a relatively narrow temperature band, regulated between 98 and 99.5 degrees Fahrenheit (36.7 and 37.5 degrees Celsius) in a healthy human being. Extreme heat damages our cells, degrades proteins and damages DNA.
“Every time you have this, you will see the cascade of effects that cause things to stop and cause damage to your body,” Stearns said.
Our central nervous system works hard to coordinate our body’s temperature control to prevent damage. Temperature sensors in our skin and internal organs, called thermoreceptors, are specially adapted to different temperature ranges and send signals to the tactile cortex of our brain, allowing us to perceive and respond to heat, e.g. example by moving away from the sun and going indoors. .
We also have an internal thermostat located in the hypothalamus of our brain, called the preoptic area. By sensing our body’s core temperature, it can activate automatic autonomic systems to begin cooling the body when it reaches a certain temperature, for example by sweating and dilating our blood vessels.
The main way we cool down is by sweating through our sweat glands. As it evaporates, sweat cools our skin. This evaporative cooling accounts for about 80 percent of our cooling capacity during exercise, Stearns said.
Sweating, however, is a “double-edged sword,” Laitano said. “This is very important because it will help you regulate temperature, but it also leads to dehydration.”
Our brain’s internal thermostat also activates the sympathetic nervous system, causing the blood vessels in our skin to dilate. Our heart more than double its production to meet increased demand and pumps warm blood from our body’s core to the surface, where it should cool – if the air outside is not warmer.
Hot, humid days are particularly dangerous when it comes to heatstroke because they tax our natural thermoregulation abilities. Hot air raises our skin temperature instead of lowering it, and the higher the humidity, the harder it is for our sweat to evaporate and cool us down.
The two types of heatstroke
There is two types of heatstroke: classic heat stroke and exertional heat stroke.
Classic heat stroke is caused by passive heating from the external environment, such as during heat waves. It usually affects children and the elderly who are less able to regulate their body temperature. In young children, the sweat glands may not be fully developed. And with age we begin to lose our abilities both feel thirsty And thermoregulate Effectively.
Exertional heat stroke occurs when we exert ourselves physically with strenuous activity in hot weather. Physical activity heats up our skeletal muscles when it uses energy. The more intensely the muscle contracts, the more heat is produced, which warms our body from the inside in addition to the ambient heat from the environment.
Exertional heatstroke can affect anyone who engages in physical activity, but it is more likely to affect young adults, especially athletes and military personnel.
“In everyday life we don’t see a lot of this outside of competition scenarios, because people are smart and they will stop if they don’t feel good, before they reach the kick point heat,” Stearns said.
But people working in sports and military contexts may be motivated to exceed their thermoregulatory limits. Exertional heat stroke is the third leading cause of death among athletes during physical activity, behind heart problems and head or neck trauma.
It is estimated that the mortality rate from exertional heat stroke could be approximately 27 percentwhile mortality linked to classic heat stroke could be much higher, due to its predominance in already vulnerable people.
How heatstroke can damage the brain
Early data shows that 10 to 28 percent of patients who survive heat stroke may long-term cognitive or neurological damagenotably involving a dysfunction of the cerebellum, a brain region important for the coordination of our movements.
Brain imaging months or years after heatstroke has also revealed damage to cells in the cerebellum and other areas of the brain, including the hippocampus, midbrain, and thalamus, may also be damaged.
“This is going to sound really sad. It’s very rare to have someone who suffers long-term from heat stroke and survives,” Stearns said. “Unfortunately, most of these cases perish. But there are many cases that require lifelong care.
How to prevent and treat heat stroke
Give yourself time to acclimatize to the heat and stay hydrated. “The first 10 to 15 days of anyone doing a new activity in a warm environment are really important to do it gradually. Because you give your body time to adapt,” Stearns said.
Do not exercise alone outside and learn to recognize signs of heatstroke in yourself and in others. Getting away from the heat, even for a few hours, is protective during heatwaves. Air conditioning and electric fans can help, but they are not always available, for example during a power outage. Sprinkling the skin with water may be a effective alternative.
If you feel unwell, weak, confused or agitated, these are all “red flags,” Stearns said. Stumbling, collapsing, or being unable to coordinate your movements are also signs to watch for in yourself and others around you.
Start cooling immediately, even before a full diagnosis, if heat stroke is suspected, experts say. “There’s a big association between how quickly you cool someone down and the prognosis, what the outcome is,” Laitano said.
You can apply ice wrapped in towels to the neck, groin, or extremities. Cold water immersionwhere the person’s entire body is immersed in ice water, is the first-line treatment for heatstroke.
With better education, greater public awareness and timely treatment, “heatstroke doesn’t have to be fatal,” Stearns said.
Do you have a question about human behavior or neuroscience? E-mail BrainMatters@washpost.com and we will perhaps answer it in a future column.
