As climate changes, heatwaves and cold fronts worsen and claim lives globally: At least one study puts the death toll of around 5 million people over the past 20 years due to extreme weather. In a new study published in the journal Nature Medicine, an international team of researchers estimated that extreme temperatures killed nearly 900,000 people in major Latin American cities alone between 2002 and 2015. This is the most detailed estimate in Latin America and the first for some cities.
To estimate how many people died from high or low temperatures, researchers from the Latin American Urban Health Project looked at death data registered between 2002 and 2015 in 326 cities with more than 100,000 inhabitants. The Latin American Urban Health Project studies how urban environments and policies affect the health of urban residents in Latin America. They calculated daily average temperatures and estimated temperature ranges for each city based on a public dataset of atmospheric conditions. If deaths occurred within the 18 hottest or coldest days of the year in each city, they considered them to be related to extreme temperatures. Using a statistical model, the researchers compared the risk of dying on very hot and very cold days with the risk of dying on mild days. They found that in Latin American metropolises, nearly 6 percent of all deaths — nearly a million people — occurred on extremely hot or cold days. They also created an interactive map using data from individual cities.
When analyzing the specific causes of these deaths, the team found that extreme temperatures were often associated with deaths from cardiovascular and respiratory diseases, consistent with previous research. Extreme heat causes the heart to pump more blood, leading to dehydration and pressure on the lungs. On the other hand, extreme cold can reduce the pumping of the heart and cause low blood pressure and, in some cases, organ failure. The team also found that older adults are particularly vulnerable to extreme temperatures, with 7.5 percent of deaths in the time period covered by the study linked to extreme heat and cold temperatures. While these numbers vary from year to year, in 2015, for example, more than 16,000 deaths among nearly 855,000 people aged 65 or older could be attributed to extreme temperatures. Some estimates suggest that Latin America’s aging population will grow faster than the rest of the world — from 9 percent in 2020 to 19 percent in 2050. Although the number of deaths from extremely cold days (about 785,000) was much higher than that of extremely hot days (about 103,000), there were more severe cold days overall, which could explain the difference. But for some cities, such as Buenos Aires, Rio de Janeiro and Merida, heat is more deadly than cold: researchers estimate that on very hot days, every 1 degree Celsius increase in temperature increases the chance of dying by 5.7 percent.
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