by In 2019 alone, more than half a million people died from stroke related to high and low temperatures, a new study has found. With the world getting warmer due to man-made climate change, that number is expected to rise.
The study, published Wednesday in the medical journal Neurology, found that since 1990, the number of strokes caused by high and low temperatures has been increasing around the globe. Men had more strokes related to extreme temperatures than women, but it affected people across all age groups.
For this study, the researchers looked at temperatures and strokes in 204 countries and territories. Researchers from South Central University Xiangya Hospital in China created a model using global data on disease, death and disability and climate data that captures temperature, cloud cover and weather variables.
The authors of the study noted that the number of people with strokes has increased as the population ages and ages, but this does not account for everything. “Suboptimal temperatures” made a difference: The number of people who had strokes due to hot and cold temperatures increased and was much greater in 2019 than in 1990.
In 2019, the higher number of strokes was caused by low temperatures. Although that may be counterintuitive to global warming, cold temperatures also come with climate change. Warmer temperatures on land affect the polar vortex – the dense mass of cold air around the poles – and when it weakens, it can lead to colder temperatures.
Currently, stroke deaths associated with extreme temperatures are disproportionately concentrated in parts of the world with higher levels of people living in poverty and fragile healthcare systems, such as Africa. The study said the rapid increase in stroke burden due to high temperatures in Central Asia also requires special attention.
As the planet gets warmer, the study said, the burden of heat stroke has increased rapidly and will increase “sharply” in the future.
Temperatures are already higher here. Last year was the warmest since scientists began recording global temperatures in 1850 and temperatures are expected to break more records in the near future. This March was the hottest on record.
Dr. Mary Rice, an associate professor of medicine at Harvard Medical School who did not work on the new study, said its findings are significant.
“I really think that group did a really nice job of taking a global approach looking at historical data and bringing attention to a health issue that’s really been under-appreciated,” said Rice, a pulmonologist at Beth Israel Deaconess. Boston Medical Center. “The total burden of people dying from heat stroke is huge.”
Rice recently published a study in Frontiers in Science that found that the number of immune-mediated diseases such as allergies, asthma, autoimmune diseases and cancers is increasing due to climate change. The Rice study points to the urgent need for multi-level mitigation actions to reduce emissions and improve air quality in addressing the climate crisis.
Without immediate global action, the world will have a much greater burden of disease, she said.
‘It’s happening across the board’
Stroke is already a significant health problem. It is the third leading cause of disability worldwide, and one of the leading causes of death, earlier studies have shown.
The new study wasn’t designed to show why the extreme temperatures that accompany the climate crisis seem to cause so many strokes. Other research has shown that when the temperature is too hot, it is difficult for the body to regulate itself and cool itself by sweating. This can be the result of what doctors call the hypercoagulable state of the blood, when the blood clots more easily and the risk of stroke increases. People can also become dehydrated, which can force the heart to work too hard, increasing a person’s chance of having a stroke or heart attack.
Very cold temperatures can cause a person to have a stroke. When the body is exposed to cold, it stimulates the skin’s cold receptors which activate what is called the sympathetic nervous system, the network of nerves that control the body’s fight or flight response. This can cause vasoconstriction, the narrowing of blood vessels in the skin, arms and legs, which causes a spike in blood pressure and can lead to a stroke.
Dr. Ali Saad, a neurologist affiliated with the Climate and Health Program at the University of Colorado, said while already talking about this phenomenon with stroke patients and reminding them how dangerous extreme temperatures, especially heat can be . He said he will take their phone and add weather alerts so they are aware of when the temperature is going to drop.
“I tell them ‘I’m worried you’re going to overheat and there are things we can do to prevent a stroke and the worsening of climate change,'” said Saad.
Saad did not work on the new study, but said he hopes this latest research will get the attention of world leaders and influence public policy.
“Extreme weather, or specifically extreme temperatures, is known to be a risk factor for stroke, but what this study adds is that it’s the first to examine things on a global scale,” Saad said. “When they think of pollution or heat when it comes to health outcomes, stroke or otherwise, people tend to think of low- and middle-income countries, but it’s happening across the board and it’s expected to get worse. “
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