COVID-19 was not the first crisis in recent history to have severely impacted human longevity. The Spanish flu comes to mind, as well as major heatwaves. Understanding what sets COVID-19 apart from these other longevity crises requires not only international comparisons, but also a longer-term historical perspective. France, with over a century of detailed regional demographic data, offers a rare opportunity to take this comparative view.
In a new study, scholars of the French Institute for Demographic Studies (INED) assess the historical and spatial burden of COVID-19 in France. This means that they analysed changes in demographic data related to the pandemic, both across time and space.
The researchers did so by comparing these impacts to those of four other major longevity crises since 1900: the Spanish flu (1918-1919), the Hong Kong flu (1968-1969), and the heatwaves of 1911 and in 2003. The study uses annual death and population counts for 90 regions (French départements) coming from the French Human Mortality Database, combined with statistical modelling techniques, to estimate excess mortality related to each crisis.
To compare these events across space and time, the authors chose the “age-standardised years of life lost” (ASYLL) as the key indicator. One of the main advantages of this indicator is that it enables meaningful comparisons between different populations by relying on a common age structure. Moreover, it provides a more nuanced picture of the mortality burden than the number of deaths by considering the age at which deaths occur, and can be aggregated over multiple years to capture the full impact of each crisis.
Age patterns affect mortality data
The findings show that COVID-19 led to an average of 9 years of life lost per 1,000 inhabitants in France over 2020-2021. By comparison, the 2003 heatwave caused about 2.5 years of life lost per 1,000, the 1968-69 Hong Kong flu around 5-7 years, the 1911 heatwave 24, and the Spanish flu nearly 100. This means that despite its exceptional global scope and the societal disruption it caused, the demographic burden of COVID-19 in France appears 10 times lower than that of the most devastating crisis of the 20th century, the Spanish flu.
However, the age patterns partly explain why the overall burden of the COVID-19 pandemic, as accurately measured by ASYLL, appears lower than that of other longevity crises: deaths concentrated mainly in the population at older ages, and result in less years of life lost due to the remaining life expectancy at those ages. In contrast, the Spanish flu disproportionately affected children and young adults, whereas the heavy toll of the 1911 heatwave was largely driven by elevated infant mortality, many of these deaths linked to the consumption of contaminated milk.
Finally, the study’s sub-national analysis reveals striking contrasts in the geography of mortality. In particular, the Spanish flu was remarkably uniform in its spread, affecting all French regions with similar intensity if one excepts the north-western parts of the country. The 1911 heatwave, in contrast, had a distinctive crescent-shaped impact zone stretching across northern and south-eastern France. The 2003 heatwave left the strongest mark in the central-western part of the country. On the other side, COVID-19 stands out for its highly fragmented geography: mortality was particularly severe in the Parisian region and eastern regions bordering Belgium, Germany, and Switzerland, while parts of western France experienced little to no excess mortality.
This geographical heterogeneity is not simply a product of random variation; it underscores the crucial role of regional and local dynamics in shaping health outcomes. The marked variability in the 2003 heatwave's impact is unsurprising, given that mortality rates were highest in areas experiencing peak temperatures, especially in the central-western region; while the notable regional disparities observed during COVID-19 are likely attributable to stringent social distancing measures implemented especially during the first wave (Spring 2020), which effectively limited the virus's spread across the national territory and protected regions in the West and South. In contrast, the minimal social distancing measures during the Spanish flu were compounded by the aftermath of World War I, resulting in a devastated health system that exacerbated the pandemic's impact.
By placing COVID-19 within a century-long perspective, the study emphasises that its impact – though unprecedented in terms of media coverage and social disruption – is part of a longer history of unevenly distributed longevity crises. The study highlights the importance of examining mortality distributions in different age groups and regions in order to improve our understanding of how pandemics evolve and how we can enhance our population's resilience in the face of future health threats.