Degree of housing damage caused by the Great East Japan Earthquake and all-cause mortality in the community-based cohort study of the Tohoku Medical Megabank Project.

Background: Natural disasters may have negative health effects on survivors. However, long-term observations on this are lacking. Therefore, this study investigated the association between the degree of housing damage caused by the Great East Japan Earthquake (GEJE) and all-cause mortality using the data from the cohort study conducted by the Tohoku Medical Megabank (TMM) Project in disaster-stricken areas.

Methods: The community-based cohort study of the TMM Project which conducted a baseline survey from May 2013 to March 2016 collected data using questionnaires and blood and urine tests. The present large-scale prospective cohort study was a follow-up survey in which the degree of house damage and all-cause mortality were analysed using Cox proportional hazards regression, adjusting for sex, age and other potentially confounding variables. The degree of house damage was categorised into 'did not live in the disaster area', 'no damage', 'small-scale damage' and 'large-scale damage'. Among the 58 320 participants, 1763 deaths were confirmed during the follow-up which averaged 6.5 years.

Results: The multivariate analysis showed a hazard ratio (95% CI) of 0.96 (0.82 to 1.13) for those who did not live in the disaster area, 0.98 (0.87 to 1.10) for small-scale damage and 0.98 (0.85 to 1.14) for large-scale damage, compared with no damage, but no significant association with all-cause mortality was observed.

Conclusion: The results of this large-scale prospective cohort study of GEJE survivors showed no significant relationship between the degree of house damage and all-cause mortality. Further long-term follow-up studies are needed to examine the long-term health effects of natural disasters on survivors.