Extreme Temps Tied to Increased Stroke Death, Disability

A global increase in stroke-related death and disability has been linked to extreme temperatures related to climate change, data from a 30-year global study showed.

In the first study to assess the global stroke burden attributed to nonoptimal temperatures, investigators found that in 2019, more than 500,000 people around the world died of stroke linked to extreme temperatures — both hot and cold. The study also revealed there were 9.4 million disability-adjusted life years (DALYs) attributed to stroke because of nonoptimal temperatures. 

“Dramatic temperature changes in recent years have affected human health and caused widespread concern,” study investigator Quan Cheng, MD, of Xiangya Hospital, Central South University in Changsha, China, in a press release. “Our study found that these changing temperatures may increase the burden of stroke worldwide, especially in older populations and areas with more health care disparities.”

The findings were published online April 10, 2024, in Neurology

Ischemic vs Hemorrhagic Stroke

To investigate the relationship between nonoptimal temperature and global stroke burden, the researchers collected data from the Climate Research Unit Gridded Time Series, the World Bank, and the Global Burden of Diseases databases. These data included participants’ age, location, and sociodemographic information. 

Investigators also obtained land temperatures for 204 countries and territories from 1990 to 2019 from the Climate Research Unit Guided Time Series. For each location, the investigators calculated mean temperatures and compared them with hottest and coldest days for the regions.

Of note, researchers did not account for other stroke risk factors, such as hypertension and high cholesterol.

Of the 521,031 stroke deaths in 2019 attributed to extreme temperatures, investigators found that 474,002 were linked to low temperatures. Fewer deaths (48,000) and DALYs (1 million) were associated with extreme heat. However, stroke attributable to high temperatures also increased over three decades. 

Previous studies have shown that cold temperatures can promote vasoconstriction, leading to increased blood pressure and blood viscosity, thus increasing stroke risk. Extreme heat can cause sweating which may cause blood to hypercoagulate and promote thrombosis which, in turn, can increase stroke risk. 

In the case of heat extremes, sweating may cause the blood to hypercoagulate, which promotes thrombosis, possibly leading to stroke.

Geographically, Central Asia reported the highest stroke death rate due to hot or cold temperatures, at 18 per 100,000, with North Macedonia registering the highest national rate at 33 per 100,000. Men (7.7 per 100,000) also had a higher death rate of death from stroke than women (5.9 per 100,000). The most drastic increases in stroke death were in women in Central Asia.

Of the stroke deaths attributed to temperature extremes, 41% were intracerebral hemorrhage (IA) and 54% were ischemic (IS). DALY data showed IA accounted for 48% and IS for 44% of stroke-related disability.

Study limitations included the inability to investigate causality between temperature extremes and stroke and the inability to explore other stroke risk factors such as hypertension and high cholesterol.

The study was funded by Hunan Youth Science and Technology Talent Project. There were no disclosures. 

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