The Spanish heat paradox: temperatures soar but related deaths drop

There is a striking paradox taking place in Spain: temperatures are rising, but there are fewer deaths linked to extreme heat. As the epidemiologist Julio Díaz, 61, points out, “it is not the bullet that kills us, but the speed at which it travels.” While temperatures are rising, with the maximum daily temperature in summer increasing by around 0.4ºC every decade, so is the threshold at which heat kills – currently by 0.6º C per decade. “It’s taking more and more heat for people to die,” he says.

Díaz and his colleague Cristina Linares, 43, head the new Reference Unit on Climate Change, Health and Urban Environment set up by the Carlos III Health Institute’s National School of Health in Madrid. Their data show that, between 1983 and 2003, mortality increased by 14% for each degree above the temperature considered a heat wave, which in Madrid is 36ºC, in Córdoba 40ºC and in A Coruña 26ºC. Between 2004 and 2013, however, the situation changed: mortality rose by less than 2% for each degree above the heat wave benchmark.

“In 2003 there was a brutal heat wave,” says Díaz, indicating the turning point. “In Spain, 6,600 people died in 15 days.” It was the summer that fans sold out in Paris and Rome and around 70,000 Europeans died. To avoid this happening again, in 2004 the Spanish Health Ministry launched a national plan that introduced preventive measures and these measures have been activated every summer since. Some of the recommendations may seem obvious, such as drinking plenty of water and avoiding physical activity in the sun, but they work. Now, heat waves kill about 1,300 people a year, a figure similar to that of deaths from cold snaps, which kill about 1,050 people a year.

The threshold at which heat kills is rising by about 0.6º C per decade

Linares points out that a transformation in Spain in recent decades encompassing economic growth, the modernization of the health system, extensive building renovation, the proliferation of air conditioning systems, the creation of new green areas and prevention campaigns against high temperatures has helped the population deal with extreme heat. Spain is adapting, but the thing about keeping ahead of the bullet is that there’s no slowing down. “We have adapted, but we have to keep up this pace for the next 80 years,” says Díaz. “That’s the challenge, if we don’t want to be consumed by rising temperatures.”

Calculations made by the National School of Health unit suggest that if adaptation slows down, almost 13,000 people will die each year in Spain from heat waves between 2050 and 2100. But if the population continues its current acclimatization, deaths will be limited to about 1,400 per year, according to the researchers’ estimates. But Díaz does stress that these are merely estimates. “The important thing to remember is that deaths will increase almost tenfold if there is no adaptation,” he says.

One of the unit’s goals is to understand what is happening within cities to optimize adaptation and prevent the predicted 13,000 deaths a year. To this end, the team has begun investigating around Madrid. “We noticed that the areas where most people die are those with the lowest income levels [such as Carabanchel, Puente de Vallecas and Tetuán],” says Díaz. “Low income has more of an impact than an elderly population,” adds Linares.

“It’s not just a matter of having an air conditioner. You also have to be able to afford to turn it on”

Julio Díaz, researcher

It’s a recurring phenomenon. Last February, a mortality map of Spain coordinated by the Fisabio Foundation, a Valencia-based health research group, showed huge inequalities even on the same street regarding the risk of dying from diseases such as lung cancer and diabetes, depending on socioeconomic circumstances.

“It’s not just a matter of having an air conditioner,” says Díaz. “You also have to be able to afford to turn it on. There are people who don’t put it on because they don’t have the money.”

Díaz’s studies show large differences between provinces in beating the heat. The threshold above which heat-related deaths increase – the so-called minimum mortality temperature – has increased by an average of 0.6ºC per decade across the whole of Spain, but in Córdoba the adaptation is far greater, standing at 1.8ºC per decade. In Ciudad Real, however, the threshold has dropped to 0.27ºC per decade. “We know which provinces are adapting to the heat and which are not,” says Díaz. “Now we need to know why.”

Both Díaz and Linares stress that heat does not usually kill directly. In 2003, only 140 of the 6,600 deaths were due to heat stroke. Most of the deaths involved elderly people with underlying diseases that were exacerbated by the unusually high temperatures. Linares points out that some kinds of medication, such as those administered for Parkinson’s disease or Alzheimer’s, can aggravate dehydration and heat stroke.

“Children are not affected by the heat because their physiological condition is better than those of an elderly person, but also because there is a father or a mother around who make sure they don’t get dehydrated,” says Linares. “If a grandparent lives alone at home, no one is watching to see if he or she gets dehydrated or not.”

She points out that one of the team’s main objectives is to draw up “a vulnerability map,” showing locations in Spain that are adapting less well to extreme heat and highlighting the social, economic and demographic factors at play. “A vulnerability map is key to being able to act now and not end up with our heads in our hands later down the line,” says Linares. “We have to anticipate what we are inevitably going to go through.”

However, the two researchers emphasize that climate change is not just about soaring temperatures; it causes droughts, floods, an increase of Sahara dust in the Spanish atmosphere due to desertification, tropospheric ozone pollution and forest fires. “Deaths from heat are not going to be the problem with climate change,” says Díaz. “They will be insignificant.”

English version by Heather Galloway.