Is Climate Change Possibly Linked to Over 500K Stroke Deaths?

As climate change drives increasingly severe temperatures, stroke-related deaths worldwide may surge. Published in Neurology on Wednesday, the study suggests that in 2019 alone, climate change might have contributed to over 500,000 stroke fatalities globally.

Over the past three decades, researchers have observed a worrying trend. Climate change is driving the occurrence of extreme temperatures, not only above but also below levels considered ideal for health. The variation between hot and cold temperatures is being exaggerated on both sides.

Now, a study published by the American Academy of Neurology has identified that the majority of stroke cases occur as a result of these extreme temperatures. For very low temperatures, the result is blood vessel contraction, which increases blood pressure. High blood pressure is a well-known risk factor for developing a stroke.

But in addition, extremely high temperatures have also been linked to an increase in stroke cases. This is due to dehydration and the negative impact on cholesterol levels, which can result in slower blood flow – also a risk factor for stroke.

How researchers discovered global warming is linked to stroke

The study, published Wednesday in the medical journal Neurology, found that since 1990, the number of strokes attributable to high and low temperatures have been increasing all around the globe. Men had more strokes related to extreme temperatures than women, but it affected people across all age groups.

TOPSHOT – A woman walks along The Embarcadero under an orange smoke-filled sky in San Francisco, California on September 9, 2020. – More than 300,000 acres are burning across the northwestern state including 35 major wildfires, with at least five towns “substantially destroyed” and mass evacuations taking place.

For this study, researchers looked at temperatures and strokes in 204 countries and territories. Researchers from Xiangya Hospital Central South University in China created a model using global data on disease, deaths and disability and climate data that captures temperatures, cloud cover and weather variables.

The study authors noted that the number of people having strokes has risen as the population ages and grows, but this doesn’t account for everything. “Nonoptimal temperatures” made a difference: The number of people who had a stroke due to hot and cold temperatures grew and was significantly larger in 2019 than in 1990.

In 2019, it was low temperatures that led to the higher number of strokes. While that may sound counterintuitive for global warming, cold temperatures also come along with climate change. Warmer temperatures on land interfere with the polar vortex — the dense cold air mass around the poles — and when it is weakened, it can lead to cooler temperatures.

Right now, stroke deaths connected to extreme temperatures are disproportionately concentrated in parts of the world with with a higher levels of people living in poverty and where health care systems are fragile, like in Africa. The study said the rapid increase in stroke burden due to high temperature in Central Asia “also requires special attention.”

Dangers of extreme weather

Last summer, an estimated 45 million people in the United States faced extremely hot temperatures, as Deseret News reported. The list included Arkansas, Florida, Kansas, Louisiana, Missouri, Oklahoma and Texas. USA Today at the time described it as a “heat dome.”

In 2021, shortly after devastating cold temperatures shrouded a large swath of the country, Deseret News looked at why weather is especially hard on older adults. Both hot and cold temperatures can be deadly.

“Extreme heat or cold is no joke for older people, including older workers. And they may be in medical crisis before they even recognize it,” said Dr. Ronda McCarthy, an environmental and occupational exposure specialist near Waco, who’s on the steering committee for the Medical Society Consortium on Climate and Health, in the article.

According to the National Institute on Aging, older adults lose heat faster than younger people and yet may not realize they are cold. And being too hot can kill, too. Both can be dangerous for anyone. The difference, based on age, is what counts as extreme. Older adults can be dangerously hot in 80 degrees, or too cold below 70 degrees. That varies with the individual.

While stroke is sometimes the result, many factors can be at play. The internal thermostat of older people may not work as well as in the past, for example. And older adults may take medicine that interferes with temperature regulation. Plus, older adults are more likely than younger adults to have existing heart disease, which extreme weather can impact, including by triggering stroke.

Lila Montgomery

Lila Montgomery is a celebrated journalist who has a deep commitment to global affairs and humanitarian issues. Her extensive reporting on United Nations initiatives across the globe has brought critical stories to the forefront, stories that affect communities everywhere.