Without reaching the "so brutal" mortality of 2022, the extreme heat of this new anomalous summer has caused more than 1,800 deaths, although some estimates almost double that figure. "The impact of heat is not just a heat stroke, which is the least. The heat itself is a stress for the body."
Dominic Royé, head of Data Science at the Climate Research Foundation (FIC), and one of the authors of the Summer Heat Attributable Mortality in Spain (MACE) application that he has just launched with Aurelio Tobías, told EFE. , from the Higher Center for Scientific Research (CSIC) and Carmen Íñiguez, from the University of Valencia.
The Daily Mortality Monitoring System (MoMo) of the Carlos III Health Institute quantifies 95,904 deaths since June 1, of which 1,834 can be attributed to high temperatures.
The data reflects the maximum on August 12, with 79 deaths; the latest available are from the 22nd, when the deaths attributable to heat were 68, but it must be taken into account that they are somewhat delayed and are continually updated.
According to Royé, MACE makes a "much more modern" statistical estimate than MoMo, which continues to use a methodology from the 1990s that they have tried to update. Although it has a limitation -they are already working to solve it-, and that is that it calculates mortality at the national level without taking into account geographical differences, sex groups and age, which could be leaving out many more deaths.
MACE draws on the data on observed deaths from MoMo and the average temperature in Spain calculated by Aemet; with them, he estimates that from June 1 to August 22 there have been 8,821 deaths attributable to heat. Of these, 3,034 have occurred on days of extreme heat, of which 15 have been recorded so far.
For months, August accounts for 10 of those days and 1,883 deaths, compared to 1,151 in July, when 5 days of excessive temperatures were recorded. In June there was neither. There is a point from which the mortality curve shoots up: 26.9 ºC, explains Royé. The average temperature this summer has been 24.5º, although in August it is currently 26.2º and in July it was 25.3º.
Thus, it is once again an "extreme" summer that is now going through a fourth heat wave too late for what is usual, but it will not be "as brutal" as it was in 2022, when there were 28 days of extreme heat and 8,815 deaths from this cause. In fact, with official data from the INE, mortality shot up 20% between the months of May and August 2022 and deaths from heat stroke and dehydration doubled compared to three years earlier.
Royé recalls at this point that heat strokes barely represent between 2 and 3% of the causes of death attributable to high temperatures, that what they do above all is aggravate previous pathologies, especially cardiovascular and respiratory diseases.
The heat subjects the body to thermal stress that is aggravated at night, so that excess night temperatures increase the risk of mortality; This was revealed by a 2021 study on the "Effects of hot nights on mortality in southern Europe", of which this climatologist is co-author.
According to the article, daily mortality is associated with temperatures that exceed 20ºC at night, regardless of daytime temperatures. With the added problem, he warns, that climate change is bringing with it an increase in the maximum, but above all in the minimum.
If extreme heat has consequences for health, sleeping poorly too, so that tropical or torrid nights pose a double risk, points out to EFE Ana Teijeira, a neurophysiologist from the Spanish Sleep Society (SES).
The optimal temperature to fall asleep quality sleep is between 18 and 21 ºC and it becomes almost impossible from 24º; This fourth heat wave has left several successive lows that have touched 30º in various areas of Spain. In the short term the consequences are known, "fatigue, drowsiness, irritability, concentration problems, work performance", an exhaustion that can also cause work or traffic accidents.
But little and bad sleep also wreaks havoc in the long term, and spending so many days and even weeks with these nightly lows can "cause hormonal changes, in the immune system, in blood pressure, which can favor cardiovascular and cerebrovascular events, heart attacks, strokes...". In addition, "the sleep that we have lost these days of such intense heat at night is irretrievable" and its lack cannot be compensated when the temperatures let us rest.
What will have to be done next time? Try to maintain a regular schedule -even while on vacation-, sleep in very light and breathable clothing, try to maintain a darkness that favors rest and, most difficult, achieve an ambient temperature of between 18 and 21 ºC. And if none of that is possible, a warm shower, "not too cold" to try to lower body temperature and that the body understands that it is time to go to sleep.
