The hot summer of this year claimed many lives in Switzerland. For four weeks now, the federal statisticians have again been showing excess mortality for the 65+ age group – and this time explanations are more difficult.
Intensive care unit for Covid-19 patients. It is unclear how much of the recent excess mortality is attributable to the pandemic.
Measured by the official death toll, the worst phase of the corona pandemic has been over since this spring at the latest. And yet, since then, the statisticians have shown an unusually large number of deaths in the 65+ age group.
“Unusual” means here: The number of deaths differs significantly from expectations. The expectations are based on a statistical model: for each week, the mortality rate of the same calendar week of typically five previous years is used, changes in age structure and life expectancy are also taken into account and an expected value for the current death figures is derived from this. To estimate the expected values for 2022, the statisticians also factor out the excess mortality from the pandemic in 2020 and 2021.
pandemic and the heat
The statisticians also take random fluctuations into account. They therefore draw a range of what is expected around the theoretical expected value. Statisticians only speak of “excess mortality” or “under-mortality” when the actual number of deaths is outside the range. In the current year, three periods of excess mortality in the 65+ age group stand out: spring, summer and most recently October (see chart).
In March/April, around 950 more elderly people died than expected. This could be explained at least halfway with the pandemic. The Federal Office of Public Health (BAG) reported around 430 corona-related deaths in the period in question. In addition, data from the beginning of the pandemic suggests that the BAG numbers tended to underestimate reality. The BAG death figures from the entire winter of 2021/22 to the end of the excess mortality period in April “explained” about 70 percent of the estimated excess mortality in this period.
In the summer of this year, around 1,800 more elderly people died than was statistically expected. According to the BAG data, there were a total of around 250 corona fatalities in the period in question; even including a number of unreported cases, the pandemic should only explain a small part of the excess mortality in summer. The obvious candidate for the large part is the summer heat. The summer of 2022 was that second warmest summer in recent decades; only the record summer of 2003 was even hotter.
The heat is considered a risk factor, especially for cardiovascular diseases. There was also excess mortality in the record summer of 2003 and in the equally hot summer of 2015. Factoring out the corona effect, the estimated excess mortality in summer 2022 in relation to the overall older population is likely to have been at a similar level as in the record summer of 2003.
After the end of this year’s summer, mortality fell back into the normal range. But at the end of September the picture changed again. According to the data published on Tuesday for the week ending October 23, excess mortality in the age group 65+ has been observed for four weeks in a row. In total, around 760 more people died than expected during this period. The heat cannot serve as an explanation for this. And the BAG reports a total of “only” 65 corona fatalities for the period in question; the effective number would have to be more than ten times higher to explain the recent excess mortality.
In the realm of guesswork
Neither federal representatives nor external experts were able to give any conclusive explanations on Tuesday. “You just don’t know,” said one of the respondents. A possible “explanation” would be random fluctuations. The fact that a period of four weeks in a row with significant excess mortality corresponds to coincidence is not impossible from a statistical point of view, but very unlikely. In addition, also point foreign calculationswhich, according to federal information, are based on a different procedure, for Switzerland and some other countries there will be excess mortality for this autumn.
The often lamented shortage of staff in the healthcare system could increasingly leave its mark on the death statistics. But this is currently considered very speculative. However, several observers suspect that the testing and reporting discipline in relation to Corona has decreased. wastewater data provide some clues. However, discipline would have to have dropped massively this fall for the pandemic to be considered a significant direct cause of the recent excess mortality.
Hansjakob Furrer, chief physician and director at the University Clinic for Infectious Diseases at the Inselspital in Bern, sees a connection with the pandemic. According to Furrer, in the second phase of a Covid-19 infection there is a clear immune reaction, which can cause a relatively long-lasting inflammatory state in the body. This is a particular burden for older and chronically ill people, even if those affected do not notice it very much themselves. Even without a clinically acute condition, older people could die from it, emphasizes Furrer.
In this reading, there have been more hidden Covid-19 deaths recently than before. Whether this provides the main explanation for recent excess mortality is unclear. Perhaps a combination of named and unknown factors makes the difference. Conclusive findings are still awaited.