Observed-expected differences in life expectancy during the COVID-19 pandemic

Abstract Background Although Japan effectively controlled COVID-19 in 2020 and 2021 through public health efforts, mortality surged in 2022, possibly due to low herd immunity. In contrast, countries like the UK exhibited different trends. This study aims to clarify the impact of COVID-19 on life expectancy by analyzing the relationship between the early and later phases of the pandemic. Methods We analyzed life expectancy (LE) data from approximately 200 countries and the EU27. Expected LE values for 2020 to 2022 were projected using linear regression based on data from 2015 to 2019. Observed-expected differences (OED) were then calculated for each year. Results OEDs in 2020 and 2022 were as follows: Australia (+0.21, -0.05), New Zealand (+0.19, +0.50), Norway (+0.17, -0.93), Hong Kong (+0.12, -2.22), Denmark (+0.09, -0.51), Japan (+0.06, -0.77), South Korea (+0.05, -1.29), Finland (-0.13, -1.19), France (-0.81, -1.07), EU27 (-1.03, -1.17), UK (-1.16, +0.37), US (-1.75, -1.36), and Kuwait (-2.85, +0.43). Correlation coefficients of OEDs between 2020 and 2022 were -0.166 (p = 0.33) for very high-income countries (GNI per capita > $40,000), and significantly positive for upper-middle (0.468, p < 0.001), middle (0.532, p < 0.001), and low-income (0.612, p < 0.001) countries. Conclusions In some countries, life expectancy exceeded expected values in 2020 despite the pandemic, but most experienced negative deviations by 2022. Among very high-income countries, the negative, though non-significant, correlation between 2020 and 2022 suggests challenges in sustaining effective long-term pandemic control and the possible consequences of low herd immunity. In contrast, among countries other than very high-income countries, those that implemented effective control measures in the early phase tended to show better outcomes in the later phase, suggesting that early pandemic response can have lasting positive effects. Key messages • In some countries, life expectancy exceeded expected values in 2020 despite the COVID-19 pandemic. • By 2022, life expectancy in most of those countries had dropped below projected levels, reflecting possible delayed impacts.