The long-run effects of pandemic influenza on the development of children from elite backgrounds: Evidence from industrializing Japan

This study estimates the lingering effects of fetal exposure to the 1918 influenza pandemic on the development of secondary school and girls’ high school students in industrializing Japan. In order to refine the verification of the fetal origins hypothesis, we tried not only to focus on children from elite schools but also to construct the continuous influenza mortality measure using monthly variations in the number of births and influenza deaths. By utilizing a nationwide multidimensional physical examination dataset, we found that fetal exposure to influenza in the pandemic years reduced the heights of boys and girls by approximately 0.3 cm and 0.1 cm, respectively. While the strongest negative magnitude was observed in the pandemic period, the lingering relapses in the post-pandemic period still had considerable adverse effects on height. In relation to the lowest decile group which experienced normal influenza mortality in non-pandemic years, the heights of the boys and girls who experienced pandemic influenza in the womb are approximately 0.6 and 0.3 cm lower. The lingering influenza relapse in the post-pandemic period has an adverse effect on the boys’ height, accounting for roughly 80% of the maximum pandemic effect.