Rate of Asthma Prescriptions for Children and Adolescents During the 2018 Floods in Japan

Abstract

BACKGROUND AND OBJECTIVES Victims of natural disasters are exposed to air pollution, changes in living conditions, and physical/emotional stress, which leads to exacerbation of asthma. The study aimed to examine the association between being victims of a natural disaster and asthma medication prescriptions among children and adolescents by comparing those affected and unaffected by the 2018 Japan floods. METHODS Within the most severely impacted regions, a 1-year postdisaster retrospective cohort study was conducted on the basis of the National Health Insurance Claims Database. Participants aged 0 to 19 years with no record of asthma treatment in the year preceding the disaster were included in the analysis. The cumulative incidence of newly prescribed asthma inhalers in the 12 months after the disasters was compared between victims and nonvictims using survival analysis. To test the robustness, a difference-in-differences analysis was performed, including participants with a history of asthma prescriptions. RESULTS Of the 1 176 171 participants included in the study, 4425 (0.40%) were assigned to the victim group. Of these, 287 individuals (6.4%) from the victim group and 59 469 individuals (5.6%) from the nonvictim group were newly prescribed asthma inhalers within the year after the floods. Survival analysis revealed that victims were more prone to receiving inhaler prescriptions compared with nonvictims (adjusted hazard ratio 1.30; 95% confidence interval 1.16–1.46). Consistent results were obtained from the difference-in-differences analysis. CONCLUSIONS The 2018 Japan floods increased the demand for asthma inhalers among flood victims, underscoring the general implication that natural disasters can increase the incidence of asthma.