Auteur : Agence Science Presse – Rabéa Kabbaj
Skeptics about the pandemic keep repeating the same criticism. They claim it has killed less people than the official death toll. So they conclude it was overblown for nothing. The Rumour Detector explains what the concept of “excess mortality” means.
The origin of one of the rumours
On April 20, Québec passed the symbolic threshold of 1000 lives taken by COVID-19. Most of them occurred in long-term care centres known as CHSLDs. At that time, Québec’s Director of Public Health, Horacio Arruda, as reported in Le Soleil, said that “every year, in normal times, about 1000 people a month die in CHSLDs”.
Some people jumped on this statement. They concluded that the real impact of COVID-19 was negligible. They also claimed the measures implemented to contain it, such as the lockdown, had been useless.
Québec isn’t the only place where the question is being raised. In the United States and elsewhere, some have cast doubt on the severity of the death toll blamed on the pandemic. Maybe some people just had the bad luck to die in the same week and the same living environment as a contaminated person, they say. Were they counted as “COVID deaths”? Or were people infected with COVID at their time of death, but would have died anyway because of their poor health?
There’s a way to confront this argument. Compare the number of deaths for comparable periods. For example, compare April 2020 to April 2019. Or compare the first few months of 2020 to the first few months of the 10 previous years.
The Institut de la statistique du Québec published data at the end of May and the beginning of June that shows excess mortality. For men or women, the number of deaths per week in 2020, starting in mid-March, exceeded the weekly totals for the previous years. The death toll peaked in the week of April 26 to May 2. (The last data available, at the time this article was written, stops at May 9).
Robert Bourbeau, Professor of Demography at the Université de Montréal, explains. “Based on the data provided, I took the average for the past three years, 2017, 2018 and 2019. The result was 3155 excess deaths” for the period from March 15 to May 9, 2020.
This isn’t far from the official COVID death toll of 3471, for the same period. The “overestimate” of 300 isn’t a problem, Professor Bourbeau explains in an interview. “A variance of close to 300 deaths out of a surplus over 3000 isn’t huge.”
The Institut de la statistique du Québec published an update on June 18, including data up to May 23. It confirms the previous estimates. In the second and third weeks of May, the total deaths gradually approached the average for the past few years. But it was still above that average.
A small percentage of the people who died would probably have died of other causes if the pandemic hadn’t killed them. Every year, for example, about a hundred Quebecers die of the seasonal flu during the period concerned. But this year, practically none were counted.
On the other hand, all the excess deaths aren’t necessarily caused by COVID. The concept of “excess mortality” is widely used in demography and epidemiology. It doesn’t only include people who die from a disease. It also includes deaths resulting from the collateral effects. That’s because fewer people consult doctors or go to emergency rooms, Robert Bourbeau explains. On the other hand, a positive collateral effect could be imagined. For example, fewer fatal traffic accidents during the lockdown.
But the net result was excess mortality in Québec between March and May 2020.Is this the best comparative tool?
The World Health Organization (WHO) defines excess mortality as “mortality that is attributable to the crisis conditions”. This concept seems to have gained notoriety since the start of the pandemic. Many argue that it would give a more accurate picture than the COVID-19 death toll alone.
A preprint paper on “Excess Mortality from COVID-19” was published in mid-May. According to its two authors: “Neither Covid-19 death counts, nor proportion of deaths among confirmed cases are appropriate to compare between population groups within countries or between countries.” They compared weekly deaths in Sweden, by age and sex, for the first few months of 2020, compared to the equivalent months of the past five years. They also concluded that: “The Covid-19 pandemic has so far had a clear and consistent effect on total mortality in Sweden.” Starting from the first week of April, the mortality rate for each age bracket over 60 years is higher by 75% among men and 50% among women.
The independent British body The Health Foundation also recommends using excess mortality as a measuring tool. That’s because it “does not depend on how COVID-19 deaths are recorded”. Recording methods vary from country to country.
Since the beginning of the pandemic several media have compiled and updated data on excess mortality for different countries and regions, wherever these figures are available. These media include the Financial Times and The Economist in Great Britain and the New York Times in the United States. Most of the European countries, such as France and Belgium, show mortality “peaks” that are very clearly above average. They generally began in mid-March and extended to May. For some countries, like the United States, the curve was still above-average at the beginning of June.
Much of this data is preliminary. We will have to wait months for a complete picture.
This text was updated on June 19 with the paragraph on the new data from the Institut de la statistique du Québec up to May 23.