A recent epidemiological study, currently available on the medRxiv* preprint server, demonstrates that all-cause mortality was mostly unchanged during the coronavirus disease (COVID-19) pandemic compared to the previous four years in Norway and Sweden – two countries which took very different routes in their battle against this disease.
The total confirmed cases of COVID-19 around the world, caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), now stands at over 54.82 million infections, with over 1.32 million deaths and 35.21 million recoveries (as of November 16, 2020).
Nonetheless, a precise assessment of the COVID-19 burden has been hindered by the lack of comprehensive data on the disease and the benefits and harms of the measures implemented against it. Moreover, cause-specific death rates can be prone to bias, particularly for a disease with a high asymptomatic burden and testing/reporting differences.
Hence, all-cause mortality trends may give us a much more reliable alternative for appraising the burden of an epidemic in different countries and regions, as well as national strategies that can differ substantially.
Norway and Sweden are kindred countries in regards to ethnicity, administrative systems, socioeconomics, and public health care systems. Furthermore, both have reliable, stringent, timely, and comprehensive registration of deaths.
In the fight against COVID-19, Norway implemented harsh and extensive measures (such as lock-downs and school closures) and reported lower burden of severe cases and few COVID-19 associated deaths. Conversely, Sweden had a much less intrusive strategy but has been criticized for reporting more COVID-19 associated disease and deaths.
In Sweden, however, mortality was overall lower than expected in the months preceding the epidemic. This sets the stage for a natural experiment and opens the door for specific difference-in-difference analyses.
The opportunity was embraced by researchers from Norway and Sweden, led by Dr. Frederik E Juul from the Clinical Effectiveness Research Group at the Oslo University Hospital and the University of Oslo. They decided to dive deep into data and compare the effect of different national strategies on all-cause and COVID-19 associated mortality.