Health
When heat waves turns deadly: How extreme temperatures affect the human body
As temperatures and humidity soar outside, what’s happening inside the human body can become a life-or-death battle decided by just a few degrees.
The critical danger point outdoors for illness and death from relentless heat is several degrees lower than experts once thought, say researchers who put people in hot boxes to see what happens to them.
With much of the United States, Mexico, India and the Middle East suffering through blistering heat waves, worsened by climate change, several doctors, physiologists and other experts explained to The Associated Press what happens to the human body in such heat.
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Heat waves can raise your body temperature
The body’s resting core temperature is typically about 98.6 degrees Fahrenheit.
That’s only 7 degrees away from catastrophe in the form of heatstroke, said Ollie Jay, a professor of heat and health at the University of Sydney in Australia, where he runs the thermoergonomics laboratory.
Dr. Neil Gandhi, emergency medicine director at Houston Methodist Hospital, said during heat waves anyone who comes in with a fever of 102 or higher and no clear source of infection will be looked at for heat exhaustion or the more severe heatstroke.
A man pours cold water onto his head to cool off on a sweltering hot day in the Mediterranean Sea in Beirut, Lebanon, on July 16, 2023. As temperatures and humidity soar, what’s happening inside the human body can become a life-or-death battle decided by just a few degrees. (AP Photo/Hassan Ammar, File)
“We routinely will see core temperatures greater than 104, 105 degrees during some of the heat episodes,” Gandhi said. Another degree or three and such a patient is at high risk of death, he said.
How heat kills
Heat kills in three main ways, Jay said. The usual first suspect is heatstroke — critical increases in body temperature that cause organs to fail.
When inner body temperature gets too hot, the body redirects blood flow toward the skin to cool down, Jay said. But that diverts blood and oxygen away from the stomach and intestines, and can allow toxins normally confined to the gut area to leak into circulation.
“That sets off a cascade of effects,” Jay said. “Clotting around the body and multiple organ failure and, ultimately, death.”
But the bigger killer in heat is the strain on the heart, especially for people who have cardiovascular disease, Jay said.
It again starts with blood rushing to the skin to help shed core heat. That causes blood pressure to drop. The heart responds by trying to pump more blood to keep you from passing out.
“You’re asking the heart to do a lot more work than it usually has to do,” Jay said. For someone with a heart condition “it’s like running for a bus with dodgy (hamstring). Something’s going to give.”
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The third main way is dangerous dehydration. As people sweat, they lose liquids to a point that can severely stress kidneys, Jay said.
Many people may not realize their danger, Houston’s Gandhi said.
Dehydration can progress into shock, causing organs to shut down from lack of blood, oxygen and nutrients, leading to seizures and death, said Dr. Renee Salas, a Harvard University professor of public health and an emergency room physician at Massachusetts General Hospital.
“Dehydration can be very dangerous and even deadly for everyone if it gets bad enough — but it is especially dangerous for those with medical conditions and on certain medications,” Salas said.
Dehydration also reduces blood flow and magnifies cardiac problems, Jay said.
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Heat also affects the brain. It can cause a person to have confusion, or trouble thinking, several doctors said.
“One of the first symptoms you’re getting into trouble with the heat is if you get confused,” said University of Washington public health and climate professor Kris Ebi. That’s little help as a symptom because the person suffering from the heat is unlikely to recognize it, she said. And it becomes a bigger problem as people age.
One of the classic definitions of heat stroke is a core body temperature of 104 degrees “coupled with cognitive dysfunction,” said Pennsylvania State University physiology professor W. Larry Kenney.
Heat and humidity are a dangerous duo
Some scientists use a complicated outside temperature measurement called wet bulb globe temperature, which takes into account humidity, solar radiation and wind. In the past, it was thought that a wet-bulb reading of 95 Fahrenheit was the point when the body started having trouble, said Kenney, who also runs a hot box lab and has done nearly 600 tests with volunteers.
His tests show the wet-bulb danger point is closer to 87. That’s a figure that has started to appear in the Middle East, he said.
And that’s just for young healthy people. For older people, the danger point is a wet bulb temperature of 82, he said.
“Humid heat waves kill a lot more people than dry heat waves,” Kenney said.
When Kenney tested young and old people in dry heat, young volunteers could function until 125.6 degrees, while the elderly had to stop at 109.4. With high or moderate humidity, the people could not function at nearly as high a temperature, he said.
“Humidity impacts the ability of sweat to evaporate,” Jay said.
How to cool down heat exhaustion patients
Heatstroke is an emergency, and medical workers try to cool a victim down within 30 minutes, Salas said.
The best way: Cold water immersion. Basically, “you drop them in a water bucket,” Salas said.
But those aren’t always around. So emergency rooms pump patients with cool fluids intravenously, spray them with misters, put ice packs in armpits and groins and place them on a chilling mat with cold water running inside it.
Sometimes it doesn’t work.
“We call it the silent killer because it’s not this kind of visually dramatic event,” Jay said. “It’s insidious. It’s hidden.”
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Long before the Black Death killed millions across Europe in the Middle Ages, an earlier, more elusive version of the plague spread across much of Eurasia.
For years, scientists were unsure how the ancient disease managed to spread so widely during the Bronze Age, which lasted from roughly 3300 to 1200 B.C., and stick around for nearly 2,000 years, especially since it wasn’t spread by fleas like later plagues. Now, researchers say a surprising clue may help explain it, a domesticated sheep that lived more than 4,000 years ago.
Researchers found DNA from the plague bacterium Yersinia pestis in the tooth of a Bronze Age sheep discovered in what is now southern Russia, according to a study recently published in the journal Cell. It is the first known evidence that the ancient plague infected animals, not just people, and offers a missing clue about how the disease spread.
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“It was alarm bells for my team,” study co-author Taylor Hermes, a University of Arkansas archaeologist who studies ancient livestock and disease spread, said in a statement. “This was the first time we had recovered the genome from Yersinia pestis in a non-human sample.”
A domesticated sheep, likely similar to this one, lived alongside humans during the Bronze Age. (iStock)
And it was a lucky discovery, according to the researchers.
“When we test livestock DNA in ancient samples, we get a complex genetic soup of contamination,” Hermes said. “This is a large barrier … but it also gives us an opportunity to look for pathogens that infected herds and their handlers.”
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The highly technical and time-consuming work requires researchers to separate tiny, damaged fragments of ancient DNA from contamination left by soil, microbes and even modern humans. The DNA they recover from ancient animals is often broken into tiny pieces sometimes just 50 “letters” long, compared to a full human DNA strand, which contains more than 3 billion of those letters.
Animal remains are especially tough to study because they are often poorly preserved compared to human remains that were carefully buried, the researchers noted.
The finding sheds light on how the plague likely spread through close contact between people, livestock and wild animals as Bronze Age societies began keeping larger herds and traveling farther with horses. The Bronze Age saw more widespread use of bronze tools, large-scale animal herding and increased travel, conditions that may have made it easier for diseases to move between animals and humans.
When the plague returned in the Middle Ages during the 1300s, known as the Black Death, it killed an estimated one-third of Europe’s population.
The discovery was made at Arkaim, a fortified Bronze Age settlement in the Southern Ural Mountains of present-day Russia near the Kazakhstan border. (iStock)
“It had to be more than people moving,” Hermes said. “Our plague sheep gave us a breakthrough. We now see it as a dynamic between people, livestock and some still unidentified ‘natural reservoir’ for it.”
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Researchers believe sheep likely picked up the bacteria from another animal, like rodents or migratory birds, that carried it without getting sick and then passed it to humans. They say the findings highlight how many deadly diseases begin in animals and jump to humans, a risk that continues today as people move into new environments and interact more closely with wildlife and livestock.
“It’s important to have a greater respect for the forces of nature,” Hermes said.
The study is based on a single ancient sheep genome, which limits how much scientists can conclude, they noted, and more samples are needed to fully understand the spread.
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The researchers plan to study more ancient human and animal remains from the region to determine how widespread the plague was and which species may have played a role in spreading it.
Researchers (not pictured) found plague-causing Yersinia pestis DNA in the remains of a Bronze Age sheep. (iStock)
They also hope to identify the wild animal that originally carried the bacteria and better understand how human movement and livestock herding helped the disease travel across vast distances, insights that could help them better anticipate how animal-borne diseases continue to emerge.
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The research was led by scientists at the Max Planck Institute for Infection Biology, with senior authors Felix M. Key of the Max Planck Institute for Infection Biology and Christina Warinner of Harvard University and the Max Planck Institute for Geoanthropology.
The research was supported by the Max Planck Society, which has also funded follow-up work in the region.
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Cases of gout are rising in younger individuals, according to a global study.
The condition, which is a type of inflammatory arthritis, steadily increased in people aged 15 to 39 between 1990 and 2021, researchers in China announced.
Although rates vary widely between countries, the total number of young people with the condition is expected to continue rising through 2035.
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The study, published in the journal Joint Bone Spine, investigated 2021 data from the Global Burden of Disease (GBD), spanning 204 countries within the 30-year timeframe.
The data measured gout prevalence, incidence and years lived with disability, tracking global trends over time. The results showed a global increase across all three outcomes.
Gout is expected to continue rising in young people through 2035. (iStock)
Prevalence and disability years increased by 66%, and incidence rose by 62%. In 2021, 15- to 39-year-olds accounted for nearly 14% of new gout cases globally, the study found.
Men from 35 to 39 years old and people in high-income regions had the highest burden, but high-income North America topped the list for highest rates.
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Men were also found to have lived more years with gout due to high BMI, while women tended to have the condition as a link to kidney dysfunction, the study noted.
The total number of cases is expected to increase globally due to population growth, but the study projected that rates per population would decrease.
The researchers noted that data quality, especially in low-income settings, could have posed a limitation to the broad GBD data.
What is gout?
Gout is a common form of arthritis involving sudden and severe attacks of pain, swelling, redness and tenderness in the joints, according to Mayo Clinic. It most often occurs in the big toe.
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The condition occurs when urate crystals accumulate in the joint. These form when there are high levels of uric acid in the blood, which the body produces when it breaks down a natural substance called purines.
A gout flare-up can happen at any time, often at night, causing the affected joint to feel hot, swollen, tender and sensitive to the touch.
Urate crystals, described as sharp and needle-like, build up in the joint, causing intense pain and swelling. (iStock)
Purines can also be found in certain foods, like red meat or organ meats like liver and some seafood, including anchovies, sardines, mussels, scallops, trout and tuna, according to the Mayo Clinic. Alcoholic drinks, especially beer, and drinks sweetened with fruit sugar can also lead to higher uric acid levels.
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Uric acid will typically dissolve in the blood and pass through the kidneys into urine, but when the body produces too much or too little uric acid, it can cause a build-up of urate crystals. These are described by the Mayo Clinic as sharp and needle-like, causing pain, inflammation and swelling in the joint or surrounding tissue.
Risk factors for gout include a diet rich in high-purine foods and being overweight, which causes the body to produce more uric acid and the kidneys to have trouble eliminating it.
Experts urge patients to seek medical attention for gout flare-ups. (iStock)
Certain conditions like untreated high blood pressure, diabetes, obesity, metabolic syndrome and heart and kidney diseases can increase the risk of gout, as well as certain medications.
A family history of gout can also increase risk. Men are more likely to develop the condition, as women tend to have lower uric acid levels, although symptoms generally develop after menopause.
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Untreated gout can cause worsening pain and joint damage, experts caution. It may also lead to more severe conditions, such as recurrent gout, advanced gout and kidney stones.
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The Mayo Clinic advises patients to seek immediate medical care if a fever occurs or if a joint becomes hot and inflamed, which is a sign of infection. Certain anti-inflammatory medications can help treat gout flares and complications.
Fox News Digital reached out to the researchers for comment.
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