Demographic and public health characteristics explain large part of variability in COVID-19 mortality across countries

Abstract

Background: The numbers of coronavirus disease 2019 (COVID-19) deaths per million people differ widely across countries. Often, the causal effects of interventions taken by authorities are unjustifiably concluded based on the comparison of pure mortalities in countries where interventions consisting different strategies have been taken. Moreover, the possible effects of other factors are only rarely considered.

Methods: We used data from open databases (European Centre for Disease Prevention and Control, World Bank Open Data, The BCG World Atlas) and publications to develop a model that could largely explain the differences in cumulative mortality between countries using non-interventional (mostly socio-demographic) factors.

Results: Statistically significant associations with the logarithmic COVID-19 mortality were found with the following: proportion of people aged 80 years and above, population density, proportion of urban population, gross domestic product, number of hospital beds per population, average temperature in March and incidence of tuberculosis. The final model could explain 67% of the variability. This finding could also be interpreted as follows: less than a third of the variability in logarithmic mortality differences could be modified by diverse non-pharmaceutical interventions ranging from case isolation to comprehensive measures, constituting case isolation, social distancing of the entire population and closure of schools and borders.

Conclusions: In particular countries, the number of people who will die from COVID-19 is largely given by factors that cannot be drastically changed as an immediate reaction to the pandemic and authorities should focus on modifiable variables, e.g. the number of hospital beds.

Figure 1

Comparison of observed and predicted mortality using the final model. (A) Cross-validated predicted mortalities (i.e. calculated using a model estimated while leaving out the country for which prediction is calculated), including the 95% prediction interval (yellow bars), plotted against observed mortalities in countries under consideration. (B) With the exclusion of Qatar, Japan and Belgium. Model parameters estimated using N = 135 observations (Qatar, Japan, and Belgium excluded). The following countries are highlighted on the plot: JP, Japan; CN, China; KR, South Korea; IR, Iran; CZ, Czech Republic; DE, Germany; US, U.S.A.; FR, France; ES, Spain; BE, Belgium; SE, Sweden; UK, the United Kingdom; IT, Italy; NL, the Netherlands. Explanation of the country codes could be found in Supplementary table S.2