Standardized Mortality Ratios
Gianicolo et al. (1) provide an overview of epidemiological measures used to communicate the effects of COVID-19. With respect to the indicator mortality, we would like to point to relative comparative measures as informative statistical parameters and first applications. In fact, mortality data has not been appropriately considered so far, neither in risk communication nor in the way we analyze highly complex human–virus interactions: it is not enough to report so-called COVID-19 deaths alone.
For the highly affected country of Italy, first evaluations of standardized mortality ratios (SMRs) have been published (2). A “mortality excess loupe” was directed towards communities that registered at least 20% more deaths in March 2020 than the average for March during 2015–2019. The mortality excess loupe shows, for instance, that beyond Lombardy, SMRs increased significantly in other regions that were not suspected to be coronavirus hotspots. The SMR for men (1.96; 95% confidence interval: [1.92; 1.99]) was significantly higher than that for women (1.64 [1.60; 1.67])—a pattern that can be found in almost all included regions.
Mortality comparisons have a manifold added value and can contribute to (2):
- detect deadly epidemics or pandemics at an early stage;
- determine their severity and disease burden (3);
- monitor the spread of a virus (such as SARS-CoV-2) in a complementary manner to representative virus test results;
- evaluate both desired and undesired effects of countermeasures.
In order to understand the situation, carry out international comparisons (1), and analyze time-courses of mortality due to the COVID-19 pandemic, regular SMR comparisons over small time windows—differentiated according to region, sex, age group, and cause of death—are indicated.
Prof. Dr. med. Thomas C. Erren, MPH
PD Dr. rer. medic. Peter Morfeld
Institute and Policlinic for Occupational Medicine, Environmental
Medicine and Prevention Research, University Hospital of Cologne,
University of Cologne, Cologne, Germany
|1.||Gianicolo E, Riccetti N, Blettner M, Karch A: Epidemiological measures in the context of the COVID-19 pandemic. Dtsch Arztebl Int 2020; 117: 336–42 VOLLTEXT|
|2.||Morfeld P, Erren TC: [Deaths in nine regions of Italy in February/March 2020: „Mortality Excess Loupe“ for SARS-CoV-2/COVID-19-epidemiology in Germany]. Gesundheitswesen 2020; 82: 400–6 CrossRef MEDLINE PubMed Central|
|3.||Morfeld P, Erren TC: [Why is the “number of premature deaths due to environmental exposures” not appropriately quantifiable?]. Gesundheitswesen 2019: 81: 144–9 CrossRef MEDLINE|