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Spain is one of the countries where more heatwaves are recorded annually

A study conducted in 400 cities around the world explores the relationship between heatwaves and mortality

Spanish National Research Council (CSIC)

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IMAGE: Heatwaves recorded across the world (those lasting under 14 days in blue and over 17 days in red). view more 

Credit: MCC Collaborative Research Network

Spain has been hit by several record-breaking heatwaves this summer. In fact, Spain is one of the regions in the world where more heatwaves are recorded every year, and their effects indicate a rise in the risk of mortality of between 10% and 20% during these extremely hot periods. This is one of the conclusions which can be gleaned from an international study in which the Spanish National Research Council (CSIC) participated. The study analysed heatwaves occurring between 1972 and 2012, in 400 cities and across 18 countries, and their effects on people's health, including mortality. The results are published in the journal Environmental Health Perspectives.

"Although, from a health point of view, a heatwave is described as a day on which the temperature exceeds a certain threshold, there is no internationally agreed definition", points out scientist Aurelio Tobí­as, from CSIC's Institute of Environmental Assessment and Water Studies. Led by the London School of Hygiene & Tropical Medicine, and working within the framework of the International Multi-City and Country Collaborative Research Network Programme, this work uses -for the first time- a common methodology to evaluate the effects of these hot spells on mortality.

Among the study's conclusions is that the higher the temperature, the greater the risk to people's health. However, after analysing the data, researchers point out that the risk is similar whether high temperatures occur over several days or on a single day. In addition, the study considers that the effects on health can last for up to three to four days following a period of excessive heat.

"We have also found that people living in relatively mild or cool areas are more sensitive to hot spells of weather than those in more extreme regions. This suggests that there is some acclimatisation to these extremes of heat", Tobí­as adds.

Given that climate change projections indicate an increase in temperatures of around 2 °C and, therefore, an increase in the number of heatwaves, this study offers useful information on how to better adapt to periods of excessive heat as well as on how to develop migration strategies.

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