Occurrence of Cerebrovascular Diseases Decreased after the Great East Japan Earthquake and Tsunami of 2011

Abstract

Background: A temporary increase in the occurrence of cerebrovascular diseases (CVDs) after the Great East Japan Earthquake and Tsunami of 2011 was reported; however, no studies have been conducted to investigate long-term effects. We assessed the long-term impact of the disaster on the incidence of CVDs.

Methods: Incidence data for CVDs from 2008 to 2017 were acquired from the population-based Stroke Registry with an inventory survey of Iwate Prefecture, Japan. Part of the coastal area in Iwate Prefecture was mildly flooded and the other part was severely flooded. Age-adjusted incidence rates of CVDs (according to the Japanese standard population) were calculated for each area. The relative risk (RR) of incidence based on the years before the disaster (2008-2010), adjusted by stratified age groups, was calculated for the year of the disaster (2011), and the years after the disaster (2012-2017) in each area.

Results: The age-adjusted incidence rates gradually decreased in all areas, with the exception of a temporary increase among men who lived on the coast the year the disaster occurred. The adjusted RR in the disaster year were not significant in any area and those of the postdisaster years were 0.91 (95% CI 0.87-0.96) for all inland men, 0.93 (0.89-0.97) for all inland women, 0.85 (0.78-0.93) for all coastal men, 0.87 (0.81-0.94) for all coastal women, 0.88 (0.80-0.98) for men at mildly flooded coast, 0.82 (0.75-0.89) for women at mildly flooded coast, 0.79 (0.68-0.91) for men at severely flooded coast, and 0.98 (0.86-1.11) for women at severely flooded coast.

Conclusions: The occurrence of CVDs in the flooded coastal areas did not increase in the year of the Great East Japan Earthquake and Tsunami; furthermore, it decreased for men according to the severity of flood damage in the subsequent years; this can be attributed to supportive activities for the tsunami victims and the migration of the population.

Keywords: Cerebrovascular disease; Incidence; Stroke register; Tsunami.