During this meteorological summer (June, July and August) 21,355 more people died in Spain than expected. That was the excess mortality, which encrypts the increase in deaths over those expected at a certain time and which has broken records in the summer period. The figures have fallen drastically in September. In the absence of consolidating the data, the MoMo (the daily mortality monitoring system for all causes) of the Carlos III Health Institute (ISCIII) has shown an excess of 434, which is still somewhat above the average of that month, but it already falls within the usual parameters.
This sharp drop helps to clear up an unknown posed by the summer statistics, which only attributed 4,663 of those deaths to the heat. And no more than 20% (probably less, as will be seen later) could be directly explained by covid. But there was a majority of deaths that, on paper, did not have a clear cause. The return to more normal figures with falling temperatures reinforces the main hypothesis that many researchers had, such as health and climate expert Hicham Achebak: infrequent summer heat waves are, directly or indirectly, behind most of the excess of deaths and the MoMo algorithm (which is not based on a count, but on a calculation) is probably not prepared for such extreme temperatures for so long.
It is the explanation that they assume in the ISCIII itself. Amparo Larrauri, head of the Influenza Surveillance Unit and other respiratory viruses at the National Epidemiology Center, explains that the MoMo calculates the excess taking into account the mortality and temperature series of the previous 10 years. “At that time we had not had a heat wave of such characteristics due to its intensity, repetition and consecutive days,” she says. The model, she explains, does not take into account factors such as the health situation derived from the pandemic, the socio-health situation or the energy crisis, which means that many people have less access to refrigeration in their homes, which can result in an increase in the deaths. Never has a period of such heat coincided with a situation like the current one, which can lead to the effects being enhanced.
Larrauri also points out that for its calculations the MoMo computed the maximum temperatures, but not the minimum, which this year has also broken records: “It is what causes many homes to be subjected to very high temperatures for a long time.”
Temperature is, directly or indirectly, the biggest trigger of mortality if there are no pandemics involved. In Spain, covid aside, it usually follows a pattern: peaks in the winter months, a decrease during the spring to pick up slightly again in the summer and fall again in September. Extreme temperatures, rising or falling, help to decompensate the health of the weakest people (generally the very old) and the most vulnerable from the socioeconomic point of view, who are the ones who have fewer resources to protect themselves from both the heat like from the cold.
Covid disrupted these patterns, especially during the first year. Now it continues to kill dozens of people a day, but as Larrauri points out, the official statistics surely overestimate its lethality, since they include both people who die from covid (increasingly older and with more previous comorbidities) and those who die from covid, that is, That is, they gave a positive test, but in which the virus was not the main cause of death. With the third year of the pandemic advanced, it is an indicator that has not yet been fine-tuned.
But, to a greater or lesser extent, the coronavirus is probably, together with the heat that has also been registered in the first bars of September, which has caused this month to also be above the average mortality rate. In terms of Euromomo, which measures this statistic throughout the EU, we have gone from a “very high” excess (close to the maximum step) in summer to a “moderate” one, close to the minimum level.
But these explanations do not completely nullify other hypotheses about the rise in summer mortality, according to Salvador Peiró, director of research at the Fisabio foundation. Above all, indirect effects of covid have been considered: the saturation of the system, the lack of timely check-ups in chronic patients, the decrease in cancer screening whose consequences could now be emerging… Although there may be something to all this, the sudden rise in mortality in summer and its abrupt drop in September detract from it. “I would say that the data suggests that the heat wave has played a more important role than that attributed by the MoMo model. But this does not mean that all excess mortality is due to heat. In addition, there could be interactions between heat and other possible causes, indirectly amplifying the effect of one and the other”.
There are studies that point to an increase in cardiovascular mortality in the months following covid. “Very speculatively”, says Peiró, “the heat (which initially acts through dehydration, increasing cardiovascular, cerebrovascular, renal risks…) could increase the risk of post-Covid cardiovascular death (or vice versa, post-Covid increases the risk of death attributable to to increased temperatures).
Improve the calculation system
But to know the exact causes of mortality in these months, we will have to wait until the middle of next year. The MoMo is a mere calculation and it is the National Institute of Statistics that, with considerable delay, puts dates on the diseases that cause deaths and in what proportion. But even then, the mystery will not be completely solved. “Even when we see the causes of death we will not know very well how to interpret them. The international classification of diseases, designed by organic systems, is not designed to look for common factors (in many pathophysiological cases) between different causes of death”, adds the epidemiologist.
What the ISCIII is already working on is to continue improving the MoMo calculation. Larrauri says that it will be adjusted taking summers like this into account and that they are already adding other variables to make it more precise. “We are very happy to have a model that gives us the deaths attributable to temperature, but we believe that it can be improved, and we are going to try it. MoMo will improve especially over time, when we have many series in which there have been circumstances that can be compared, such as the pandemic or the energy crisis… An excess like this summer has probably had many contributing factors, and the heat has been a very important one”.
The phenomenon has not only happened in Spain, and has spread to a good part of Europe, which has also returned to normal in September. In one of the countries that suffered the greatest excess, the United Kingdom, there was speculation that the quality of care would drop. “Now that they have gone to the default of mortality, sensibly, nobody speculates that since Boris Johnson has been fired, the health services have started to function well and there are no longer waiting or mishandled chronic patients,” says Peiró ironically.
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Mortality in Spain returns to normal figures after an extreme summer
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