Extreme Temperatures Raise Stroke Death Risk in Low-Income Countries

Extreme temperatures raise stroke death risk in low-income countries. Both extreme heat and cold are linked to higher death rates from ischemic and hemorrhagic strokes, as found in a new study by Harvard T.H. Chan School of Public Health.

The connection between extreme temperatures and stroke deaths was more pronounced in low-income countries compared to high-income ones.

“Our findings advance the understanding of climate change’s impact on stroke,” said lead author Barrak Alahmad, a research fellow in the Department of Environmental Health.

With increasing extreme temperatures, we anticipate a rise in fatal strokes and greater disparities in stroke mortality between high- and low-income countries, with the latter being more affected by climate change.

Extreme temperatures and stroke mortality

Previous studies on the link between extreme temperatures and stroke mortality have shown mixed or inconclusive results, often focusing on single cities or high-income countries without differentiating between stroke types.

To fill these gaps, researchers used data from the Multi-Country Multi-City Network, creating a multinational database of over 3.4 million ischemic stroke deaths and 2.4 million hemorrhagic stroke deaths from 522 cities in 25 countries between 1979 and 2019.

Extreme temperatures raise stroke death risk in low-income countries. The study found that around 11 out of every 1,000 ischemic or hemorrhagic stroke deaths could be attributed to extreme temperature days.

Specifically, the coldest and hottest 2.5% of days accounted for 9.1 and 2.2 excess deaths, respectively. For hemorrhagic strokes, these extreme days contributed to 11.2 and 0.7 excess deaths, respectively.

Low-income countries also had a higher incidence of heat-related hemorrhagic stroke deaths and potentially more cold-related deaths, although this latter observation was suggestive rather than definitive.

No significant link was found between a country’s GDP and the risk of temperature-related ischemic stroke mortality.

The researchers suggested that disparities might be due to better indoor temperature control and less outdoor work in high-income countries, alongside poorer healthcare quality in low-income countries.

They emphasized the need for further research to understand the reasons behind the higher temperature-related hemorrhagic stroke mortality in low-income countries and to find effective interventions.

The study had several limitations, including a limited geographic scope with underrepresentation of rural areas and regions in South Asia, Africa, and the Middle East.

Additionally, it did not collect or analyze individual-level demographic data and focused only on stroke deaths, not non-fatal strokes. Further research on the incidence of non-fatal strokes is needed to fully understand the impact of extreme temperatures on stroke burden.

Climate change

“We urge professional stroke societies to invest in more research, especially as climate change intensifies, and to highlight emerging environmental risk factors that could make strokes — already a leading cause of death worldwide — even more lethal,” said Alahmad.

Harvard Chan co-authors included Antonella Zanobetti, Joel Schwartz, and Petros Koutrakis.

The study received support from the Kuwait Foundation for the Advancement of Science (grant CB21-63BO-01), the Medical Research Council-UK (grant MR/V034162/1), the European Union’s Horizon 2020 Project Exhaustion (grant 820655), the Swiss National Science Foundation (grant TMSGI3_211626), and the National Institutes of Health (grant R01ES034038).

Read the original article on ScienceDaily

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