The 1918 influenza pandemic and subsequent birth deficit in Japan

Abstract

Background: Recent research has documented fertility decline after the peak of pandemic-associated mortality during the 1918 influenza pandemic. Yet the time interval between the mortality peak and the dip in fertility and its contributing mechanisms remains a line of debate. Objective: This study examines the inter-temporal association between pandemic-associated mortality and subsequent birth deficit in Japan in order to shed light on the current debate about the impact of the 1918 influenza pandemic on human fertility. Methods: Seasonally and trend-adjusted monthly data on deaths, births, and stillbirths in Japan are used to compute cross-correlations between deaths, births, and stillbirths. Results: The analysis revealed a negative and statistically significant association between deaths (𝑑) at time 𝑡 and births (𝑏) at time 𝑡+9 (𝑟𝑑𝑏(9)=−.397,𝑝Conclusions: In contrast to earlier research that suggests that late first-trimester embryonic loss was the primary link between pandemic-associated mortality and future births, the findings of this paper suggest that a combination of reduced conceptions and embryonic losses during the first month of pregnancy were an important mechanism linking pandemic-associated mortality with subsequent depressed fertility.