When Donald Trump, faced with a wave of polar cold in January 2019, said that “Where the hell is global warming? Please come back, we need you,” he was entrenching his climate denialism. But above all, he showed his blindness, because global warming, climate change, was behind that cold wave. As it is also in this –or these– heat waves of the summer of 2022.
Heat waves not only bring a lot of inconvenience to everyday life. In addition, they have fatal consequences for some people. Due to the high temperatures, there are those who worsen their health and, unfortunately, some even end up dying.
heat stroke deaths
In Spain, the deaths of people affected by heat stroke when working in extreme conditions have been in the news in recent days. But these cases represent only a small percentage of deaths that can be attributed to heat.
If we go back to the summer of 2003, a period in which an intense heat wave was experienced in Spain and in other countries, some 140 people died of heat stroke. But in the months of July and August of that same year, an excess of more than 6,600 deaths was attributed to heat.
In order for a death to be officially counted as “heat stroke”, a cause of death must be included in the medical death certificate and in the death statistics bulletin, which can subsequently be assigned to code T67.0 of the International Classification. of Diseases 10th revision. The description of this code is “heat stroke and sunstroke”.
The data is not immediately known. From the time a death occurs until the cause is coded, approximately three months elapse. And the National Statistics Institute only publishes deaths by cause of death once a year. It does so once all deaths in Spain have been coded and validated. That implies that, in the middle of a heat wave, we cannot know how many lives it has taken ahead. And a few weeks later, neither. What’s more, at this point (July) the numbers from the previous year are not even known.
Only if the digital or electronic death certificate were implemented would we be able to have the figures beforehand.
So, if those are the numbers of deaths from heat stroke and, furthermore, we will not know the definitive data until the end of next year, where do those figures come from that have been spreading in the media on the number of deaths from heat from this same month?
To understand it, we must introduce the concept of attributable mortality. The aim is to estimate the impact that a risk factor, in this case temperature, has on the mortality of a population, using epidemiological measurements and analyses. It does not provide a real value, but rather an estimate made from data, these are real, on which models will be applied.
Models can be more or less accurate depending on how they are built and what parameters they are based on. The same thing that happens in weather forecasting, and that no longer amazes anyone.
This is what is applied by the MoMo system (Monitoring of daily mortality from all causes) that has existed in Spain since 2004. It was developed precisely to provide information to prevent the impact of excess temperatures on the health of the population . But it also allows indirect estimation of the impact on mortality of other important events. That is why it has become more known as a result of the covid-19 pandemic.
The MoMo system is based on:
The number of real deaths, a fact that is known. It is known with certainty and promptly how many people have been registered daily as deceased in each of the computerized civil registries that exist in Spain (which cover 93% of the population), although the coded cause of death is not available.
Daily temperatures recorded by the State Meteorological Agency at the provincial level. Another fact.
The number of inhabitants by age, sex and province, taken from the National Institute of Statistics. An “almost” real data, because it is not updated daily.
A model is applied to these real data to try to predict excess mortality from all causes and those attributable to temperature.
And with all this, and based on data from previous years, the results are calculated for each Autonomous Community and for the state total. And they are published in open access, something that has not been sufficiently valued.
The figures provided by MoMo are estimates of two aspects:
- The excess mortality that is calculated to have occurred at a specific moment in time, based on the behavior of mortality in previous periods of time.
- The attribution to the temperature of a number of deaths, based on what was published in different studies.
They are not, therefore, deaths in which a medical professional has certified the intervention of heat in the death. Do not confuse it.
What is the impact of heat on mortality?
Through systems like MoMo we can get an idea of that impact in a timely manner to act. This fulfills the practical definition of public health surveillance: information for action.
It would not make sense to wait until next year to make the estimate: then it will only have an academic interest, not a practical one.
If you want to know on this date how many deaths are attributed to temperature, you can consult it at this very moment. The system could be perfected, of course, but for now it works and it works reasonably well.