Quantitative impact of human casualties and buildings damaged by the 2011 Tohoku Earthquake off the Pacific coast on the sex ratio at birth

The sex ratio at birth among pregnant women affected by earthquakes often declines, but the disaster-related factors contributing to this change remain underexplored. This study investigates the relationship between human casualties, building damage from earthquakes, and the sex ratio at birth. Focusing on the 2011 Tohoku Earthquake, I analyzed seismic intensity, human casualties, building damage, and birth data from December 2011, nine months post-earthquake. Contrary to expectations, areas significantly impacted by tsunamis or earthquake damage in the Tohoku region did not exhibit notably low sex ratios. However, areas with higher fatalities showed a tendency toward lower sex ratios, while regions with increased fire incidents had higher sex ratios. These findings suggest that psychological stress from disasters and chemical exposure from fires may contribute to fluctuations in the sex ratio at birth. Moreover, such stressors might pose long-term health risks to survivors and their descendants. This study emphasizes the need for continued research on the health impacts of social incidents from diverse perspectives, including both biological and environmental factors.