Risk of mortality during and after the 2011 Great East Japan Earthquake and Tsunami among older coastal residents

Jun Aida,Shihoko Koyama,Takahiro Tabuchi,S V Subramanian,Toru Tsuboya,Hiroyuki Hikichi,Ichiro Kawachi,Katsunori Kondo,Yukihiro Sato,Ken Osaka,Yusuke Matsuyama

doi:10.1038/s41598-017-16636-3

Abstract

The Japan Gerontological Evaluation Study is a nationwide cohort study of individuals aged 65 years and older established in July 2010. Seven months later, one of the study field sites was directly in the line of the 2011 Great East Japan Earthquake and Tsunami. Despite the 1-hour warning interval between the earthquake and tsunami, many coastal residents lost their lives. We analyzed the risk of all-cause mortality on the day of the disaster as well as in the 38-month interval after the disaster. Among 860 participants, 33 (3.8%) died directly because of the tsunami and an additional 95 people died during the 38-month follow-up period. Individuals with depressive symptoms had elevated risk of mortality on the day of the disaster (odds ratio = 3.90 [95% CI: 1.13, 13.47]). More socially connected people also suffered increased risk of mortality, although these estimates were not statistically significant. In contrast, after the disaster, frequent social interactions reverted back to predicting improved survival (hazard ratio = 0.46 (95% CI: 0.26, 0.82)). Depressive symptoms and stronger social connectedness were associated with increased risk of mortality on the day of the disaster. After the disaster, social interactions were linked to improved survival.

Highlights

An estimated 99,700 people have lost their lives annually on average due to global natural disasters in the past decade[1]
On the day of the disaster, those living less than 1 km from the coast (Figs 1, 2, and 3a), as well as those with pre-existing severe depressive symptoms had higher mortality rates
Participants without any social interactions had higher mortality rates though it was not observed during the disaster

Summary

Introduction

An estimated 99,700 people have lost their lives annually on average due to global natural disasters in the past decade[1]. A notable exception is the Study of the Tsunami Aftermath and Recovery (STAR) conducted before and after the 2004 Indian Ocean Tsunami that killed more than 130,000 people[22]. Because their baseline survey was focused on social and economic conditions, information on health and behavioral risk factors was not collected. Older people are considered to be a vulnerable group in disaster planning policy[30,31,32], specific risk and protective factors for mortality remain poorly understood. We conducted a longitudinal assessment of risk factors for tsunami-related mortality using baseline data collected 7 months before the 2011 earthquake and tsunami

Methods

Results

Conclusion