How are the results presented?
Excess mortality can be presented as the number of additional deaths compared to what was expected (in absolute numbers or as a rate), or as a percentage increase in the expected number, mortality rate per 100,000, or age-standardised mortality rate per 100,000. When using the death tally alone, the population size or how it has changed over time are not factored in. Mortality rate per 100,000 takes into account the size of the population but does not reflect how the population has aged since 2010.
Previous calculations have found that excess mortality for the Nordic countries is overestimated when only changes in population size are considered and not changes in age composition, even in complex models (8). In this report, we have therefore chosen to express the estimates as age-standardised rates in order to reflect the changes in population size and age distribution over time. The age-standardised rates are then converted to the number of deaths. This gives excess mortality of 11.5 % in 2022 (measured as the deviation between the observed and expected number of deaths divided by the expected number of deaths) and 5.2 % in the pandemic period as a whole (2020–22).
The lower the baseline mortality, the fewer deaths are needed to show a larger percentage increase in mortality. It is therefore important to know the absolute mortality rate
How the result is presented has a considerable impact on the interpretation of excess mortality. The relative increase in mortality, i.e. expressed as a percentage, is interesting because it provides insight into how mortality has changed within different groups. In 2022, for example, we find excess mortality in all age groups except the 60–69 age group. The percentage increase in mortality was highest in the 70–79 age group.
However, the percentage increase in mortality depends on the baseline mortality: the lower this is, the fewer deaths are needed to show a larger percentage increase in mortality. It is therefore important to know the absolute mortality rate, which is much higher among those aged 90 and over (24,752 per 100,000 in 2022) than in the 70–79 age group (2,315 per 100,000 in 2022).
The media and the general population are also often concerned with the number of additional deaths, partly because it gives an indication of the increase in mortality that is intuitively easy to understand. Of these, 90 % occurred in the 70+ population, and 10 % of these were in the age group 90 years and over.