Rodrigo Perez Ortega writes via Science Magazine: With climate change, heat waves and cold fronts are worsening and taking lives worldwide: about 5 million in the past 20 years, according to at least one study. In a new study published today in Nature Medicine, an international team of researchers estimates that almost 900,000 deaths in the years between 2002 and 2015 could be attributable to extreme temperatures alone in major Latin American cities. This is the most detailed estimate in Latin America, and the first ever for some cities.
To estimate how many people died from intense heat or cold, researchers with the Urban Health in Latin America project — which studies how urban environments and policies impact the health of city residents in Latin America — looked at mortality data between 2002 and 2015 from registries of 326 cities with more than 100,000 residents, in nine countries throughout Latin America. They calculated the average daily temperatures and estimated the temperature range for each city from a public data set of atmospheric conditions. If a death occurred either on the 18 hottest or the 18 coldest days that each city experienced in a typical year, they linked it to extreme temperatures. Using a statistical model, the researchers compared the risk of dying on very hot and cold days, and this risk with the risk of dying on temperate days. They found that in Latin American metropolises, nearly 6% — almost 1 million — of all deaths between those years happened on days of extreme heat and cold. They also created an interactive map with the data for individual cities.
When the team analyzed the specific cause of these deaths in the registries, they found — consistent with previous studies — that extreme temperatures are often linked to deaths from cardiovascular and respiratory diseases. Extreme heat makes the heart pump more blood and causes dehydration and pulmonary stress. Extreme cold, on the other hand, can make the heart pump less blood and cause hypotension and, in some cases, organ failure. The team also found older adults are especially vulnerable to extreme temperatures, with 7.5% of deaths among them correlated to extreme heat and cold during the study period. Although the numbers varied from year to year, in 2015, for instance, more than 16,000 deaths — out of nearly 855,000 — among people ages 65 or older were attributable to extreme temperatures. Latin America’s aging population is projected to rise more quickly than other parts of the world — from 9% in 2020 to 19% in 2050, by some estimates (PDF). […] Although deaths on extremely cold days — about 785,000 — were much higher than those on extremely hot days — about 103,000 — overall there were more days with intense cold, which could explain this difference. But for some cities, such as Buenos Aires, Rio de Janeiro, and Merida, heat is more deadly than cold: The researchers estimated that on very hot days, the chance of dying increases by 5.7% for every 1C increase in temperature.
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