The influence of the Great East Japan earthquake on microscopic polyangiitis: A retrospective observational study

<div><p>Background</p><p>Antineutrophil cytoplasmic antibody-associated vasculitis is triggered by environmental factors, including silica dust exposure. Repeated tsunami waves brought a large volume of silica-containing sludge inland after the Great East Japan earthquake in 2011. We aimed to determine if the serious disaster influenced the clinical features of the microscopic polyangiitis.</p><p>Methods</p><p>This is an observational retrospective study conducted in a single institute. A total of 43 patients were included based on the CHCC2012 criteria for microscopic polyangiitis from 2007 to 2015. We used the Poisson regression model to determine the incidence of microscopic polyangiitis within the annual population of the medical district. The participants were selected during a 3-year period from before (N = 13) to after the disaster (N = 20). The differences of parameters and the overall survival between the groups were analyzed.</p><p>Results</p><p>The incidence of microscopic polyangiitis increased after the disaster (λ = 17.4/million/year [95%CI: 7.66–39.6] before the disaster and λ = 33.1/million/year [17.7–61.7] after the disaster, <i>P</i> = 0.044). A high Birmingham Activity Score was associated with a high incidence of microscopic polyangiitis after the disaster. The overall survival of the patients with microscopic polyangiitis declined significantly after the disaster.</p><p>Conclusions</p><p>The Great East Japan earthquake influenced the development of the microscopic polyangiitis in our restricted area. The patients who developed after the disaster had severe symptoms and a high mortality rate.</p></div

Comparison of overall survival between before and after the disaster.

<p>Survival curves were plotted to compare the mortality of each group using the Kaplan-Meier method. The dotted and solid lines indicate the time-to-events of participants before and after the disaster, respectively. The notches within the line represent the censors. The numbers at risk are illustrated below the chart. Overall survival was significantly worse in the group after the disaster (<i>P</i> = 0.029 by log rank test).</p