Comparison of pandemic excess mortality in 2020-2021 across different empirical calculations

Abstract

Different modeling approaches can be used to calculate excess deaths for the COVID-19 pandemic period. We compared 6 calculations of excess deaths (4 previously published and two new ones that we performed with and without age-adjustment) for 2020-2021. With each approach, we calculated excess deaths metrics and the ratio R of excess deaths over recorded COVID-19 deaths. The main analysis focused on 33 high-income countries with weekly deaths in the Human Mortality Database (HMD at mortality.org) and reliable death registration. Secondary analyses compared calculations for other countries, whenever available. Across the 33 high-income countries, excess deaths were 2.0-2.8 million without age-adjustment, and 1.6-2.1 million with age-adjustment with large differences across countries. In our analyses after age-adjustment, 8 of 33 countries had no overall excess deaths; there was a death deficit in children; and 0.478 million (29.7%) of the excess deaths were in people <65 years old. In countries like France, Germany, Italy, and Spain excess death estimates differed 2 to 4-fold between highest and lowest figures. The R values’ range exceeded 0.3 in all 33 countries. In 16 of 33 countries, the range of R exceeded 1. In 25 of 33 countries some calculations suggest R>1 (excess deaths exceeding COVID-19 deaths) while others suggest R<1 (excess deaths smaller than COVID-19 deaths). Inferred data from 4 evaluations for 42 countries and from 3 evaluations for another 98 countries are very tenuous Estimates of excess deaths are analysis-dependent and age-adjustment is important to consider. Excess deaths may be lower than previously calculated.SIGNIFICANCE STATEMENTExcess deaths are a key metric for assessing the impact of a pandemic. They reflect the composite impact of deaths from infection, from indirect pandemic effects, and from the measures taken. Different modeling approaches can be used to calculate excess deaths for the COVID-19 pandemic. Here, we compare four previous calculations of excess deaths and two new ones that we performed with and without adjusting for changing age structure in the estimation. Proper age-adjustment results in substantial reduction in estimates of excess deaths for 2020-2021. While results from different calculation methods are correlated, the absolute differences in estimated excess deaths are very high in most countries. Extrapolations to countries without reliable death registration is extremely tenuous.

Meaning and prediction of ‘excess mortality’: a comparison of Covid-19 and pre-Covid-19 mortality data in 31 Eurostat countries from 1965 to 2021

“…To address this problem, some authors suggest taking into account the varying age cohort composition and their specific mortality rates, thus capturing the trend towards higher mortality rates in ageing populations, for example, [ 9 , 10 ]. Conversely, however, this creates the problem that rising life expectancy is disregarded; the expected values may therefore be too high and excess mortality would be underestimated accordingly [ 11 ].…”

“…For only when a systematic assessment of the measurement error of the respective method has been carried out on the basis of comparative data can one actually validate the resulting statements on excess mortality during the Covid-19 pandemic. Indeed, several recently published papers show that the figures on excess mortality vary greatly depending on the method and its specification [ 9 , 11 , 17 , 21–23 ]. The over- and underestimates are also quite divergent for different countries, so that not only does the overall level rise or fall, but also the ranking of countries changes with the method—that is individual countries may do ‘well’ with one method and ‘poorly’ with another.…”

“…Levitt et al . [ 9 ] compare four prominent methods as well as their own age-stratified model with the finding that in the 33 countries studied, the excess mortality of all these countries together is between 1.6 and 2.8 million deaths, in the highest case almost twice the lowest estimate. For individual countries like Germany, the deviation is even more pronounced—the lowest estimate here results in 55 000, the highest in 203 000 additional deaths.…”