The researchers analysed 3.4 million ischemic stroke deaths and 2.4 million hemorrhagic stroke deaths between 1979 and 2019 across 522 cities in 25 countries
Extreme temperatures – both extreme heat and extreme cold – are associated with increased risk of stroke, a new study led by Harvard T.H. Chan School of Public Health has revealed.The study has just been published in the journal “Stroke”.
“Our findings are another step toward understanding the effects of climate change on stroke. As temperatures become more extreme, we foresee an increase in fatal strokes and a widening disparity in stroke mortality between high- and low-income countries, as the latter are likely to bear the brunt of climate change,” said lead author Barrak Alahmad, research fellow in the Department of Environmental Health. While previous studies have been small in size with often inconclusive findings, the database of this present study was made up of 3.4 million ischemic stroke deaths and more than 2.4 million hemorrhagic stroke deaths, reported between 1979 and 2019 across 522 cities in 25 countries.
“The study found that for every 1,000 ischemic or hemorrhagic stroke deaths, about 11 were attributable to extreme cold or hot days. Of those 11 deaths, the coldest and hottest 2.5% of days contributed to 9.1 and 2.2 excess deaths, respectively. Out of every 1,000 hemorrhagic strokes, the coldest and hottest 2.5% of days contributed to 11.2 and 0.7 excess deaths. The study also found that low-income countries bore a higher burden of heat-related hemorrhagic stroke mortality than high-income countries and may bear a higher burden of cold-related hemorrhagic stroke mortality as well (though evidence was suggestive, not conclusive). It did not find a relationship between countries’ gross domestic product and risk of temperature-related ischemic stroke mortality,” the school said in a statement.
However a limitation of the study was the fact that rural settings and countries in South Asia, Africa, and the Middle East were underrepresented.
