Sweat and blood
Humans, like mammals, are warm-blooded animals. In order for our cells, tissues and organs to function properly, our body temperature must be between 36 and 37 degrees C. (Most people have a temperature of 36.6 degrees C.) The thermoregulation center, which is located in a region of the brain called the hypothalamus, tries to maintain this body temperature and acts like a thermostat. “When the blood reaches it and its temperature is too high, but also too low for everything in the body to function properly, it sends a signal to various organs to take action,” says Alicja Sapała-Smoczyńska.
Then we start to sweat. We owe effective cooling to a dense network of 2 to 5 million sweat glands, which are located shallowly under the surface of the skin, but are not attached to hair follicles, as in other mammals. They secrete a watery fluid that goes directly onto the heated skin. It evaporates quickly, dissipating excess heat. Then we feel pleasantly cool. The sweat glands can produce up to two liters of watery fluid per hour. “So we lose water with sweat. When it runs out, we stop sweating. This is a situation that favors overheating, that is, the state before a stroke,” explains Dr. Sapała-Smoczyńska. Such people feel unwell, may experience dizziness and dark spots before their eyes. That is why it is so important to drink plenty during hot weather – at least 2.5 liters of water per day.
Sweating isn’t the only way to cool down. When we get too hot, we start panting like dogs to get rid of the heat with exhaled air. The heart then beats faster and the blood vessels dilate. This is why our face turns red in the heat. “The blood vessels under the epidermis dilate to increase the amount of fluid for sweat production, because the sweat produced on the skin is a fluid transported by the blood vessels,” explains Alicja Sapała-Smoczyńska. When the blood vessels dilate, less blood flows to the internal organs, including the brain. This explains why when we are hot we have no energy, feel sleepy, irritable and have difficulty concentrating.
The most important thing is water
When the thermoregulation system cannot cool effectively, a stroke occurs. In the first phase, the face turns red. Only in the second phase of a stroke, when the thermoregulation center is disturbed, do the face and hands turn pale. This results in a mechanism called centralization of circulation. The brain directs all blood to important organs such as the heart, kidneys, and liver to save lives. The body temperature can be raised to 40 or even 41 degrees C – this can, for example, help fight infections, but the core body temperature remains under the control of the thermoregulation centers located in the hypothalamus of the brain. “In a person with a stroke, the mechanisms for dissipating heat to the environment become inefficient and thermoregulation control is ineffective,” says Alicja Sapała-Smoczyńska. When the cooling system stops working and the body temperature rises by only 0.5 degrees C to 41.5 degrees C, nerve cells are damaged. At 42-43 degrees C, irreversible changes occur in proteins.
– Therefore, when we become very pale and not red during the heat, it is a sign that we have had heatstroke and that the situation is very worrying – says Alicja Sapała-Smoczyńska. – People who have had a stroke feel strange. They feel stuffy, hot and may have a headache. It is not always associated with a stroke, but if it increases and is accompanied by other symptoms, it indicates a stroke. These symptoms include dizziness, a feeling of rapid heartbeat and a feeling of muscle weakness – we can raise our hand, but it will be extremely difficult for us.
When we become very pale and not red during the heat, it is a sign that we have suffered from heatstroke and the situation is very worrying – Alicja Sapała-Smoczyńska, pediatrician, travel medicine doctor
Other distressing symptoms include nausea, vomiting, and a faster heartbeat. The person experiencing this may become very anxious. You should then move the person to a cool place as soon as possible and give them water. This will allow the body to recover and the thermoregulation mechanism to start working properly. The person should not be cooled with cold water, as this can cause the muscles to shiver and the blood vessels in the skin to constrict, which will increase heat production.
During hot weather, it is best to drink water with electrolytes such as sodium, potassium, calcium and magnesium, which we lose through sweat. Electrolyte deficiency can lead to serious health problems. For example, too little sodium in the body can cause headaches, confusion and even seizures. Potassium deficiency can cause muscle weakness, cramps and irregular heart rhythms, too little calcium can cause tremors and magnesium deficiency can cause irregular heart rhythms and muscle weakness.
You can also drink fruit and vegetable juices. They contain glucose, which nourishes the body. And thanks to their high water and electrolyte content, they can effectively support the body’s hydration, especially on hot days or during intense physical activity. They not only quench thirst and provide excellent hydration, but also provide essential vitamins, minerals and antioxidants, says Wanda Baltaza, Ph.D., clinical nutritionist.
Tomato juice is an excellent source of potassium, thus contributing to the maintenance of water and electrolyte balance. It also contains valuable lycopene, a natural antioxidant. Carrot juice, on the other hand, is rich in beta-carotene and vitamin A. It also contains potassium, magnesium, phosphorus and calcium.
– But the most important thing is to provide the stroke patient with plenty of water as soon as possible – adds Alicja Sapała-Smoczyńska. She also advises observing such a person for the next 24 hours. – If the next day he still has a headache, does not want to eat and feels weak, it is a sign that the person has not returned to his previous shape after the incident. Then the help of a doctor would be useful, says Alicja Sapała-Smoczyńska.
Tropical nights
It is not known how many people suffer from heat stroke, including sunstroke. Most of them do not need medical help and do not go to the hospital. They are recovering on their own. All we know is that a stroke can happen to anyone, regardless of age and health status. However, the most vulnerable are children under one year of age, whose thermoregulatory center is not yet fully developed, as well as children up to preschool age and the elderly, whose thermoregulatory mechanism is already developed, but does not function efficiently enough to prevent stroke.
– Heatstroke also threatens people of all ages who have chronic diseases or patients with psychiatric illnesses who take neuroleptics. These drugs weaken the thermoregulation center, says Alicja Sapała-Smoczyńska. – A large group of stroke patients are children who are so active on hot days and so absorbed in playing that they do not notice how hot they are. That is why we remind caregivers to call their children back from time to time. They gave them something to drink and told them to calm down.
Overheating or heatstroke can occur not only outdoors, but also in a heated apartment or car without air conditioning. The problem is both the daytime heat, when temperatures reach 40 degrees C, and the tropical nights, when the outside temperature does not drop below 20 degrees C and which do not bring any relief. We sleep poorly – the sleep is shallow and the body does not regenerate. Such nights do not provide rest.
Aggression, anxiety and infectious diseases
In 2021, scientists presented an analysis in “Nature Climate Change” showing that in the years 2000-2019, 489 thousand people died every year due to heat in the world. people. High temperatures torment not only the inhabitants of hot Africa and Asia, but also Europeans. In July of this year, in the journal Nature, a team of scientists led by Joan Ballester of the Institut de Salud Global de Barcelona estimated that almost 63 thousand people will die due to heat in Europe in 2022. people, most of them in Mediterranean countries. But the heat will increasingly bother residents of colder regions of Europe. Estimates show that more than 6 thousand people may die every year in Poland due to excessively high temperatures. people.
Hot weather doesn’t just lead to heatstroke or sunstroke. Excessive heat also aggravates chronic diseases, such as cardiovascular and kidney disease, diabetes and asthma. It affects mental health, leaving people confused, anxious and even aggressive. And warmer days and nights throughout the year increase the risk of tick-borne diseases, as mild winters provide the perfect breeding ground for these arachnids. We will also be increasingly affected by infectious diseases that were previously associated with the tropics, such as cholera, dengue fever and West Nile virus. All of this is a consequence of global warming, the effects of which are felt mainly in the summer.
The boiling era
Almost 10 years ago, the first report on how global warming is affecting the health of Europeans was published in the Lancet. It was prepared by more than a hundred climate and health scientists from 52 research institutions and UN agencies, including the World Health Organization (WHO) and the World Meteorological Organization (WMO). An updated version was released in July this year. It shows that Europe is warming faster than the rest of our planet and that the average annual temperature on our continent is 1 degree C higher than the global average.
The report also shows that people around the world are increasingly facing extreme heatwaves, which are getting longer each year. There are twice as many hot days today as there were in the second half of the 20th century. And it’s about to get even worse. This June was the hottest June on record. The average air temperature on our planet was 16.66 degrees C, 0.67 degrees C higher than the average for this month in 1991-2020. In Poland, June was also hotter than before. The average air temperature was 18.4 degrees C, 1.6 degrees higher than the 1991-2020 average.
It was also extremely hot in July. A preliminary analysis presented by Dr. Karsten Haustein, a climatologist at the University of Leipzig, shows that the global average temperature last month was 1.3-1.7 degrees C higher than the average temperature for this month since measurements began. This is 0.2 degrees C higher than the previous record set in July 2019.
There is every indication that the whole of 2024 will break the record set last year, when people were exposed to potentially dangerous high temperatures for an average of 86 days. Heat-related deaths among people over 65 increased by 85% between 2013 and 2022 compared with 1991 and 2000. The authors of the latest report published in the Lancet estimate that by the middle of this century, five times more people will die from extremely high temperatures than ever before. “The era of global warming is over, the era of global boiling has arrived,” warned UN Secretary-General António Guterres at a press conference in late July.
