Two complementary approaches to estimate an excess of mortality: The case of Switzerland 2022

ObjectiveDuring the COVID-19 pandemic, excess mortality has generally been estimated comparing overall mortality in a given year with either past mortality levels or past mortality trends, with different results. Our objective was to illustrate and compare the two approaches using mortality data for Switzerland in 2022, the third year of the COVID-19 pandemic. MethodsUsing data from the Swiss Federal Statistical Office, standardized mortality rates and life expectancies in 2022 were compared with those of the last pre-pandemic year 2019 (first approach), as well as with those that would be expected if the pre-pandemic downward trend in mortality had continued during the pandemic (second approach). The pre-pandemic trend was estimated via a Poisson log-linear model on age-specific mortality over the period 2010-19. ResultsUsing the first approach, we estimated in Switzerland in 2022 an excess mortality of 2.6% (95%CI: 1.0%-4.1%) for men and 2.5% (95%CI: 1.0%-4.0%) for women, while the excess mortality rose to 8.4% (95%CI: 6.9%-9.9%) for men and 6.0% (95%CI: 4.6%-7.5%) for women using the second approach. Age classes over 80 were the main responsible for the excess mortality in 2022 for both sexes using the first approach, although a significant excess mortality was also found in most age classes above 30 using the second approach. Life expectancy in 2022 has been reduced by 2.7 months for men and 2.4 months for women according to the first approach, whereas it was reduced by respectively 8.8 and 6.0 months according to the second approach. ConclusionsThe excess mortality and loss of life expectancy in Switzerland in 2022 are around three times greater if the pre-pandemic trend is taken into account than if we simply compare 2022 with 2019. These two different approaches, one being more speculative and the other more factual, can also be applied simultaneously and provide complementary results. In Switzerland, such a dual-approach strategy has shown that the pre-pandemic downward trend in mortality is currently halted, while pre-pandemic mortality levels have largely been recovered by 2022.

Automated summary

During the COVID-19 pandemic, two different approaches were used to estimate excess mortality in Switzerland in 2022. The first approach compared mortality rates and life expectancies in 2022 with the pre-pandemic year 2019, while the second approach compared them with the pre-pandemic downward trend in mortality. According to the first approach, excess mortality rates were 2.6% and 2.5% for men and women, respectively, while the second approach showed higher rates of 8.4% and 6.0%. The main cause of excess mortality in 2022 was age classes over 80 according to the first approach, and significant excess mortality was also found in most age classes above 30 using the second approach. Overall, considering the pre-pandemic trend resulted in three times higher excess mortality and loss of life expectancy compared to simply comparing 2022 with 2019.