Overall and cause-specific excess deaths during the COVID-19 pandemic

Background The COVID-19 pandemic led to seven million officially reported deaths worldwide. However, certified death counts do not fully capture the true impact of the pandemic, as they exclude both deaths not officially attributed to COVID-19 and the indirect consequences of disrupted health systems. To fill this gap, researchers have focused on excess mortality, defined as the difference between observed and expected deaths based on historical data. This report presents three studies estimating excess mortality from all causes and specific causes across multiple countries from 2020 to 2023, focusing on demographic and healthcare-related differences. Methods Study 1 assessed total excess mortality and regional disparities in Europe (2020-2023) using weekly death counts from the Short-Term Mortality Fluctuations data series and associations with socioeconomic indicators. Study 2 examined all-cause and cause-specific excess deaths in 30 countries worldwide in 2020, using World Health Organization data. Study 3 analyzed the association between COVID-19 cases and monthly cause-specific mortality in 16 countries, using data obtained directly from national statistical offices. Spearman's correlation coefficient (rs) was derived to quantify these associations. Excess deaths were calculated as the difference between observed and expected deaths. Expected deaths were estimated using quasi-Poisson regression models, including demographic and temporal factors and population size as a correction. The 95% confidence intervals for excess deaths were derived from Monte Carlo simulations. Results Between 2020 and 2023, 1,642,586 excess deaths (+8.0%) were recorded in 29 European countries, peaking in 2021 (+11.2%). The annual excess was +10.0% in 2020, +8.6% in 2022, and +2.1% in 2023. Central and Eastern Europe experienced a higher overall increase at +13.2% than other regions. The proportion of the population living below the poverty line and the Gini index were directly associated with increased excess mortality, while GDP per capita, health expenditure and the proportion of people fully vaccinated by the end of 2021 and 2022 were inversely associated. About 1.4 million excess deaths from all causes across 30 selected countries worldwide in 2020 (+12.2%) were estimated. Significant excess deaths from ischemic heart disease and cerebrovascular diseases were observed in a third of the countries, from diabetes in 19 countries and from ill-defined causes in 20 countries. A positive correlation was found between COVID-19 cases and monthly excess mortality from all causes in all countries considered (0.61≤rs≤0.91), from cardiovascular disease (CVD) in 11 countries (0.45≤rs≤0.85) and from diabetes in 13 countries (0.42≤rs≤0.79). No excess mortality was estimated for cancer in any of the countries considered. Conclusion In Europe, half a million excess deaths occurred annually in each of the first three years of the pandemic, with only a modest excess observed in 2023. Significant excess mortality was recorded worldwide for all-cause mortality, CVD and diabetes, with peaks in COVID-19 cases closely aligning with these excess deaths while no increase in cancer-related mortality was observed. The response to COVID-19 highlighted large inequalities in health outcomes, influenced by public health policies, demographic structures, socio-economic factors and health infrastructure.