Long-term mortality rate changes and inverse patterns for pandemic and post-pandemic excess mortality

The COVID-19 pandemic and pandemic response may have long-term consequences. The cumulative impact may be better appraised when post-pandemic years are also considered. For 38 populations with reliable death registration data, we estimated excess deaths for 2020–2025 with granular age stratification. One model (Fa) compared deaths against the mean of 2017–2019. Three other trend models considered changes in mortality rates after 2003 (or after a country reached $20,000 per capita income) factoring trend-of-trends (TTa), including shrinkage (STTa), and factoring also the 2024–2025 data for trend-of-trends calculation (STTa⁺). Slopes (weighted mean -0.62%/year in 2019) and slopes-of-slopes (weighted mean +0.104%/year²) for age-stratified mortality rates were highly heterogeneous across populations. On model average, 4 populations (Luxembourg, Ireland, Sweden, New Zealand) had cumulative death deficits during 2020–2025, while another 6 (Chile, Bulgaria, Japan, Greece, Slovakia, Italy) had >4% excess deaths. Differences were more prominent during 2020–2023, while 33/38 countries had death deficits in 2024–2025. Total 2020–2025 excess deaths were 0.92–2.49 million (2020–2023: 1.99 –2.88 million; 2024–2025: a deficit of 0.39–1.08 million). Lack of age stratification and use of unchanged linear trends for the baseline (as in Lee-Carter modeling) grossly biased excess death estimates upwards. Socioeconomically more vulnerable populations had higher pandemic deaths, but a more pronounced post-pandemic death deficit. Excess death estimates require careful consideration of changing population age structure and long-term mortality trajectories. Post-pandemic deficits, especially in more vulnerable populations, may reflect pandemic deaths of people with modest life expectancy, paid off in 2024–2025.