Disease and fertility: Evidence from the 1918-19 influenza pandemic in Sweden

Early-Life Disease Exposure and Its Heterogeneous Effects on Mortality Throughout Life: Sweden, 1905-2016

Exposure to infectious diseases in early life has been linked to increased mortality risk in later life in high-disease settings, such as eighteenth- and nineteenth-century Europe. Less is known about the long-term effects of early-life disease exposure in milder disease environments. This study estimates heterogeneous effects from disease exposure in infancy on later-life mortality in twentieth-century Sweden, by socioeconomic status at birth and sex. Using historical population data for southern Sweden, we study 11,515 individuals who were born in 1905-1929 from age 1 until age 85. We measure exposure to disease using the local post-early neonatal mortality rate in the first 12 months after birth and apply flexible parametric survival models. For females, we find a negative effect on life expectancy (scarring) at ages 1-85 following high disease exposure in infancy, particularly for those born to unskilled workers. For males, we find no negative effect on later-life survival, likely because stronger mortality selection in infancy outweighs scarring. Thus, even as the incidence of infectious diseases declined at the start of the twentieth century, early-life disease exposure generated long-lasting negative but heterogeneous population health effects.

Did the 1918 influenza pandemic cause a 1920 baby boom? Demographic evidence from neutral Europe

In 1919-20, the European countries that were neutral in the First World War saw a small baby bust followed by a small baby boom. The sparse literature on this topic attributes the 1919 bust to individuals postponing conceptions during the peak of the 1918-20 influenza pandemic and the 1920 boom to recuperation of those conceptions. Using data from six large neutral countries of Europe, we present novel evidence contradicting that narrative. In fact, the subnational populations and maternal birth cohorts whose fertility was initially hit hardest by the pandemic were still experiencing below-average fertility in 1920. Demographic evidence, economic evidence, and a review of post-pandemic fertility trends outside Europe suggest that the 1920 baby boom in neutral Europe was caused by the end of the First World War, not by the end of the pandemic.

The (temporary) Covid-19 baby bust in Mexico

In this paper, we investigate whether fertility and newborn health changed during the Covid-19 pandemic in Mexico. We use national administrative data and an event-study design to examine the impact of the Covid-19 pandemic on fertility and newborn health characteristics. Our findings suggest that Mexico's fertility declined temporarily as measured by conceptions that likely occurred during the stay-at-home order. Initially, the general fertility rate fell by 11-12 per cent but quickly rebounded and returned close to its original levels by the end of 2021. Newborn health also deteriorated during the pandemic. Instances of low birthweight and prematurity substantially increased, with both remaining elevated over the entire pandemic period.

What can we learn from historical pandemics? A systematic review of the literature

What are the insights from historical pandemics for policymaking today? We carry out a systematic review of the literature on the impact of pandemics that occurred since the Industrial Revolution and prior to Covid-19. Our literature searches were conducted between June 2020 and September 2023, with the final review encompassing 169 research papers selected for their relevance to understanding either the demographic or economic impact of pandemics. We include literature from across disciplines to maximise our knowledge base, finding many relevant articles in journals which would not normally be on the radar of social scientists. Our review identifies two gaps in the literature: (1) the need to study pandemics and their effects more collectively rather than looking at them in isolation; and (2) the need for more study of pandemics besides 1918 Spanish Influenza, especially milder pandemic episodes. These gaps are a consequence of academics working in silos, failing to draw on the skills and knowledge offered by other disciplines. Synthesising existing knowledge on pandemics in one place provides a basis upon which to identify the lessons in preparing for future catastrophic disease events.

Socioeconomic mortality differences during the Great Influenza in Spain

Despite being one of the deadliest viruses in history, there is limited information on the socioeconomic factors that affected mortality rates during the Great Influenza Pandemic. In this study, we use occupation-province level data to investigate the relationship between influenza excess mortality rates and occupation-related status in Spain. We obtain three main results. Firstly, individuals in low-income occupations experienced the highest excess mortality, pointing to a notable income gradient. Secondly, professions that involved more social interaction were associated with a higher excess of mortality, regardless of income. Finally, we observe a substantial rural mortality penalty, even after controlling for income-related occupational groups. Based on this evidence, it seems that the high number of deaths was caused by not self-isolating. Some individuals did not quarantine themselves because they could not afford to miss work. In rural areas, home confinement was likely more limited because their inhabitants did not have immediate access to information about the pandemic or fully understand its impact due to their limited experience handling influenza outbreaks.

Human fertility after a disaster: a systematic literature review

Fertility is a key demographic parameter influenced by disaster. With the growing risk of disasters, interest in the fertility response to a disaster is increasing among the public, policy makers and researchers alike. However, a systematic literature review on how disaster affects live birth counts does not yet exist. We reviewed 50 studies retrieved from a systematic search based on a pre-registered protocol. We found an overall negative impact of disasters on fertility. If any, increases in fertility were mostly linked with weather-related physical disasters. We also identified 13 distinct mechanisms which researchers have considered as underlying the fertility effects of disaster. By contrast to the common belief that disasters are more likely to increase fertility in contexts with already high fertility, we found little evidence to suggest that the total fertility rate of the studied populations was an important predictor of the direction, timing or size of fertility impacts. While this may be because no relationship exists, it may also be due to biases we observed in the literature towards studying high-income countries or high-cost disasters. We summarize the methodological limitations identified from the reviewed studies into six practical recommendations for future research. Our findings inform both the theories behind the fertility effects of disasters and the methods for studying them.

COVID-19 as a game-changer? The impact of the pandemic on urban trajectories

Will the COVID-19 pandemic interrupt the recent European urbanization trends - and if so - what is the magnitude of this sudden shock, and how deaths, births, and net migration contribute to this disruption? Until now, most discussions on the topic have circled either around the anecdotal evidence of city center decline, or contrarian speculations about residential inertia and the forthcoming business-as-usual. Bringing clarity to the uncertainty and confusion surrounding COVID-19, this paper seeks to detect overarching patterns in and the magnitude of its sudden shock to long-term urban trajectories, understood as a reversal of the pre-pandemic population development trend, across European cities in the early 2020s. It reveals that during the first year of COVID-19, population growth in European cities significantly slowed down to -0.3 % per annum, with 28 % of all European cities having experienced a U-turn from population growth to loss. Out-migration was the main driver of such rapid urban shrinkage, while excess mortality associated with COVID-19 has also contributed to population loss in several European city-regions; some, especially, smaller cities suffered from a significant drop in birth rates. Based on the factorial, hierarchical, and temporal dimensions of the COVID-19 crisis, the paper provides a plausible forecast about the future of Europe's post-coronavirus city.

Tropism and Infectivity of Pandemic Influenza A H1N1/09 Virus in the Human Placenta

Influenza virus infection in pregnant women may put the fetus at higher risk; however, to date, there has been no detailed research about the expression of influenza virus receptors in the human placenta. We employed the lectin staining technique, which is a classic influenza virus receptor research method for studying the distribution of viral receptors in the human placenta. In addition, we examined the susceptibility of the human placenta to H1N1/09, by detecting viral proteins and RNA at different time points post-infection. We found that the human placenta expressed both avian and human influenza A virus receptors (α-2, 3-linked sialic acid and α-2, 6-linked sialic acid). In addition, H1N1/09 did not only infect the human placenta, but also replicated and was released into the culture media. We concluded that the human placenta is susceptible to the 2009 influenza A virus (H1N1/09) infection, and that particular attention should be paid to shielding pregnant women from infection during influenza season.

Unequal excess mortality during the Spanish Flu pandemic in the Netherlands

A century after the Spanish Flu, the COVID-19 pandemic has brought renewed attention to socioeconomic and occupational differences in mortality in the earlier pandemic. The magnitude of these differences and the pathways between occupation and increased mortality remain unclear, however. In this paper, we explore the relation between occupational characteristics and excess mortality among men during the Spanish Flu pandemic in the Netherlands. By creating a new occupational coding for exposure to disease at work, we separate social status and occupational conditions for viral transmission. We use a new data set based on men's death certificates to calculate excess mortality rates by region, age group, and occupational group. Using OLS regression models, we estimate whether social position, regular interaction in the workplace, and working in an enclosed space affected excess mortality among men in the Netherlands in the autumn of 1918. We find some evidence that men with occupations that featured high levels of social contact had higher mortality in this period. Above all, however, we find a strong socioeconomic gradient to excess mortality among men during the Spanish Flu pandemic, even after accounting for exposure in the workplace.

Effects of pandemics uncertainty on fertility

The COVID-19 pandemic has affected various dimensions of the economies and societies. At this juncture, this paper examines the effects of pandemics-related uncertainty on fertility in the panel dataset of 126 countries from 1996 to 2019. For this purpose, the World Pandemics Uncertainty Indices are used to measure the pandemics-related uncertainty. The novel empirical evidence is that pandemics-related uncertainty decreases fertility rates. These results are robust to estimate different models and include various controls. We also try to explain why the rise in uncertainty during the COVID-19 pandemic has resulted in the fertility decline.

Reevaluating the Long-Term Impact of In Utero Exposure to the 1918 Influenza Pandemic

Almond (2006) argues that in utero exposure to the 1918 influenza pandemic reduced the 1919 birth cohort's adult socioeconomic status (SES). We show that this cohort came from lower-SES families, which is incompatible with Almond's cohort-comparison identification strategy. The adult SES deficit is reduced after background characteristics are controlled for; it is small and statistically insignificant in models that include household fixed effects. Replicating Almond's state-level dose-response analysis, we find no evidence in census data that influenza exposure reduced adult SES. Evidence from a city-level dose-response analysis on educational attainment using WWII enlistees from 287 cities is mixed.

Socioeconomic Disparity in Birth Rates During the COVID-19 Pandemic in New York City

Introduction: The differential impact of the coronavirus disease 2019 (COVID-19) pandemic across race, ethnicity, and socioeconomic status remains poorly understood. While recent explorations into birthrates during the pandemic have revealed significant declines, how birthrates may have differed between racial and socioeconomic subgroups during the pandemic remains to be detailed. Methods: Using electronic health records from a large hospital network in New York serving a racially and socioeconomically diverse population, we explored birthrates associated with conceptions that occurred during the COVID-19 pandemic lockdown for demographic and obstetric differences. Results: Two thousand five hundred twenty-three unique patient deliveries corresponded with conceptions that occurred during the COVID-19 pandemic lockdown in New York. Compared to the same period the previous year, there was a 22.85% decrease in births. Explorations into differences in birthrates by socioeconomic status revealed that much of the decline could be explained by fewer births among individuals living in higher socioeconomic status as opposed to individuals living in urban economic poverty [χ²(n = 5588) = 18.35, p < 0.01]. Conclusion: On March 22, 2020, New York instituted a prohibition of all nonessential social gatherings and the closure of all nonessential businesses. Although the full impact of the COVID-19 pandemic on reproductive health and outcomes remains largely unknown, the decreased birthrate associated with the initial COVID-19 wave in New York was not entirely unexpected. While the mechanisms that drive health disparities are complex and multifactorial, most of the decrease occurred among those living in higher socioeconomic status. This finding has important implications for understanding health behaviors and disparities among minorities living in low socioeconomic status.