Climate Change Is Making Strokes More Frequent And Deadly, Warns World Stroke Organization

Climate change poses an escalating threat to brain health, with extreme heat, rapid humidity shifts and exposure to dust and sandstorms increasing the risk of having a stroke, according to a scientific statement by experts from the World Stroke Organization.

Published in the International Journal of Stroke, the statement summarises the latest evidence on the association between stroke and the environmental factors exacerbated by climate change, including extreme temperatures, temperature variability, humidity, dust and sandstorms, among others.

Senior lead author Anna Ranta, professor from the University of Otago's department of medicine, New Zealand, and a member of the World Stroke Organization's board of directors, said an unstable climate increases the risk both of having a stroke and of patients dying as a result.

"Temperature extremes and rapid swings in temperature, humidity and air pressure have a physiological effect on the human body. Hot temperatures can cause dehydration, 'thickening' the blood and raising the risk of blocked blood vessels, while humidity and air pressure changes can increase blood pressure, an important cause of stroke," Ranta said.

"Absolute changes in temperature and variations in temperature, barometric pressure and humidity -- patterns that are intensifying as a result of climate change -- all have an impact on stroke risk," the author said.

Researchers reviewed previously published studies that assessed associations between stroke and environmental variables, including extreme temperatures and compound weather events.

They found older adults, workers frequently exposed to the weather, and those in low and middle-income countries to be at a higher risk of stroke from environmental factors.

Compound weather events, such as when extreme heat and drought, or cold, humidity and wind come together, were found to have an additive effect, increasing the risk of stroke and mortality even further, Ranta said.

The senior lead author added, "Air pollution is another big factor in increasing the risk of stroke, with more than 20 per cent of strokes globally attributed to air pollution." Ranta said that while transport and industrial emissions are primarily a cause, rather than an effect of climate change, increases in frequency and severity of wildfires, sand and dust storms have been directly linked to climate change.

"The particulate matter of the 'air pollutants' enter the blood stream via the lungs and cause damage to blood vessel walls. This can result in blocked and ruptured brain arteries and cause a stroke," the author said.

The statement reads, "Cold exposure, temperature variability, and extreme thermal events were most consistently associated with increased stroke risk." It said that while effects due to cold were generally stronger than those due to heat, heat effects have been increasing over time.

The statement recommended stepping up efforts to cut carbon emissions by promoting clean energy, plant-rich diets and educating patients about how the weather can impact health.

Hospital electronic health records and public messaging should include temperature and other climate-related alerts, the authors said.

Meteorological agencies, environmental scientists, urban planners and emergency services should work together to develop coordinated policies for preparedness, early warnings, and responses to climate-related stroke hazards, the team said.

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