Disasters can exacerbate socioeconomic health disparities because of differential exposure (e.g., socioeconomically disadvantaged groups are more likely to be exposed to disaster-related trauma) and differential vulnerability (disadvantaged groups are more likely to suffer health consequences of exposure to trauma). We sought to test whether health disparities among older adults widened in the area which was directly affected by the 2011 Great East Japan Earthquake & Tsunami compared to areas which largely escaped tsunami damage. We used data from a cohort of community-dwelling older adults who were directly affected by the 2011 disaster (the Iwanuma Study) and municipalities that were not directly affected (the JAGES parent cohort excluding Iwanuma city). The Iwanuma Study gathered pre-disaster information from participants in 2010 (seven months before the disaster) as well as post-disaster information in 2013, 2016 and 2019 (2.5, 5.5 and 8.5 years after the disaster). Our outcomes were depressive symptoms (GDS) and instrumental activities of daily living (IADL). We examined the pre- versus post-disaster trends in socioeconomic health disparities using the slope index and relative index of inequality. We then conducted a difference-in-difference analysis comparing the pre/post disaster change in health disparities in the "exposed" city (Iwanuma) compared to "control" cities. We found clear pre-disaster socioeconomic inequalities in both GDS and IADL in both the exposed and control cities. However, the magnitude of these inequalities did not change after the disaster on either the absolute or relative scales. The 2011 disaster in northeastern Japan did not exacerbate pre-existing patterns of health inequalities in the older population.
Keywords: Health inequality; depressive symptoms; disaster; instrumental activities of daily living; socioeconomic status.