Third longest heatwave on record in Spain leaves 1,149 people dead

A record high temperature of 45.8C was recorded in Jerez de la Frontera (Cadiz province in Andalucía) last Sunday, which was the hottest day of the heatwave that finally started to cool down on Tuesday. According to Spain's Aemet state meteorological agency spokesperson José Ángel Núñez, 17 August was the hottest day of this episode, which started on 3 August and lasted 16 days, with seven official Aemet stations recording over 45C.

This August heatwave was the third longest since records began, tying with two others that took place in 2003 and 2022. Sunday also stands out as the day with the highest number of deaths related to high temperatures - 125 deaths in a single day. In total, this episode - the second this year - has resulted in 1,149 deaths attributable to high temperatures.

So far this summer, there have been 2,635 deaths caused by excess temperatures, according to the daily mortality monitoring system (MoMo) of the Carlos III health institute. They already exceed by more than 600 those of the whole of last summer, when there were 2,012 deaths. However, the record of 2022 - a year characterised by long-lasting heatwaves - of 4,789 deaths has not yet been beaten this summer.

It is important to note that not all of these deaths are from a heatstroke, which is the cause in a minor number of cases. "Most of these deaths are due to the fact that most people have some kind of underlying illness and the heat contributes to their deterioration," says Alberto Ruano from the University of Santiago de Compostela. Researcher Aurelio Tobías from the CSIC council of investigations adds that heat "is a trigger for older, vulnerable people with underlying pathologies", which end up being the main cause of death.

For this reason, what MoMo publishes daily are estimates based on data from the civil registry for the whole of Spain, which are compared with the deaths of the last ten years to determine whether there is excess mortality. In order to determine the mortality rate attributable to atmospheric temperatures, a specific variable is added that changes depending on each territory. It was this system that detected an increase in deaths when Covid-19 started to spread, as researcher Diana Gómez Barroso from the Carlos III institute states.

Like other experts, Gómez highlights that older people, especially those over the age of 85, are more susceptible to health issues caused by the heat, because high temperatures aggravate their underlying pathologies. While "there is still a month to go" in a summer that has already exceeded the number of deaths registered in the entire summer of 2024, the temperatures during the rest of August and September will determine how the final statistics will change.

According to Ruano, heat-related mortality is on the rise, which, to some extent, is due to the fact that the population is getting older and, therefore, more vulnerable to high temperatures. On the other hand, Aurelio Tobías, who developed the MACE application to calculate heat-related mortality, says that the risk of mortality associated with high temperatures is decreasing, as the population adapts, both biologically and through socio-economic factors.

Researcher Natalia Shartova says that, given its progress in recent years, heat-related mortality is likely to continue being "an important public health problem" this summer. She insists on coordination between institutions as necessary in the implementation of public policies to mitigate the effects of heat on mortality.