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.
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.
Of the 1 073 170 participants included in the study, 4425 (0.40%) were assigned to the victim group. Of these, 287 individuals (6.5%) 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.
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.
Comments
As the correlation between pollen dispersal and asthma deaths in 1995 shows, the increase in asthma exacerbation during the 2018 Japan floods, might be also associated with increased pollen dispersal.
Comment by: Akira Awaya[1,2*] and Yoshiyuki Kuroiwa[3-5]
1 Dermatology & Epidemiology Research Institute (DERI), 4978 Totsuka-cho, Totsuka-ku, Yokohama, Kanagawa 244–0003, Japan
2 Department of Genome System Science, Yokohama City University, Seto 22–2, Kanazawa-ku, Yokohama, Kanagawa 236–0027, Japan
3 Department of Neurology and Stroke Center, University Hospital Mizonokuchi, Teikyo University School of Medicine, 5–1-1, Futago, Takatsu-ku, Kawasaki, Kanagawa 213–8507, Japan
4 Department of Medical Office, Ministry of Finance, Japanese Government, 3–1-1, Kasumigaseki, Chiyoda-ku, Tokyo 100–8940, Japan
5 Department of Neurology, Yokohama City University Graduate School of Medical Sciences, 3–9, Fukuura, Kanazawa-ku, Yokohama 236–0004, Japan
We pay our respects to Utsumi et al. for their efforts to prevent the onset and exacerbation of asthma based on data analysis, and for the many suggestions they have left us regarding disease prevention. However, we would like to point out that their description of air pollution is seriously lacking in consideration. I would like to discuss the fact that they have not paid attention to or considered the issue of pollen exposure, which seems to have nothing to do with air pollution caused by natural disasters. As revealed in epidemiological studies of asthma deaths in Japan, the sharp increase in asthma deaths that appeared in 1995 was a phenomenon that should be noted, as asthma deaths had been on a steady decline since the introduction of inhaled drug therapy in the 1970s-1980s. However, this issue was dealt with in a simple way, probably because of the influenza epidemic, and it has not been looked at again since.
The author collected data on influenza outbreaks in Kanagawa Prefecture and created graphs showing the trends in outbreaks. As these graphs show, there was no characteristic sharp increase in asthma deaths in the years of the 1993 influenza pandemic or the many influenza pandemics that occurred after 1995. Therefore, we believe that the theory that the sudden increase in asthma deaths in 1995 was due to the influenza epidemic is not correct.
In four reports on the correlation between the dynamics of KD incidence and annual fluctuations in the number of pollen grains dispersed, the author pointed out that, based on surveys up to 2005, the year with the highest number of pollen grains dispersed in Japan was 1995.
In response to exposure to large amounts of pollen, KD has resumed its trend of rapid increase since 1995. Where asthma deaths had been on a downward trend until 1994, we have assumed that patients who died of asthma in 1995 were also afflicted by a sudden worsening of symptoms as a result of the large amount of pollen exposure in 1995. In addition to the fact that the number of pollen grains dispersed in Tokyo in 2018 was the third highest since 2005, the year with the highest number of pollen grains dispersed, it has also been reported that the number of patients with KD in Hiroshima Prefecture increased in 2018 & 2019. Therefore, in the same way as an increase in asthma deaths in 1995, we need to consider the effects of pollen exposure in relation to the worsening of asthma symptoms in 2018.
We would like to suggest that Utsumi and others analyse the pollen data and consider the impact of pollen, which should also contribute to the increase in the number of people suffering from asthma due to flooding. We recommend that disaster victims in particular pay attention to daily pollen information, wear masks and goggles to avoid pollen, and use air purifiers.
References：
1. Dobashi K. Epidemiology of asthma (including asthma deaths). This referred to Executive
summary: Japanese guidelines for adult asthma (JGL) 2006. Nihon Naika Gakkai Zasshi, 2006 95:1417〜1424. (The Japanese Society of Internal Medicine).
2. Awaya A, Sahashi N. The etiology of Kawasaki disease: does intense release of pollen
induce pollinosis in constitutionally allergic adults, while constitutionally allergic infants develop Kawasaki disease?. Biomed Pharmacother. 2004;58(2):136-140.
3. Awaya A, Nishimura C. A combination of cross correlation and trend analyses reveals that Kawasaki disease is a pollen-induced delayed-type hyper-sensitivity disease. Int J Environ Res Public Health. 2014;11(3):2628-2641. doi:10.3390/ijerph110302628.
4. Awaya A. Suppressive influence of seasonal influenza epidemic on Kawasaki disease
onset. Nihon Rinsho Meneki Gakkai Kaishi. 2016; 39(6):528-537. doi:10.2177/jsci.39.528.
5. Awaya A, Kuroiwa Y. The Relationship between Annual Airborne Pollen Levels and Occurrence of All Cancers, and Lung, Stomach, Colorectal, Pancreatic and Breast Cancers: A Retrospective Study from the National Registry Database of Cancer Incidence in Japan, 1975–2015. Int. J. Environ. Res. Public Health 2020;17:3950.
Introduction of our background:
With regard to the number of patients in Japan who have suffered from Kawasaki disease （KD）, we noticed from the graph showing the trend since 1970 that there were three characteristic peaks of increase around 1990. We also compared the fluctuations in the two graphs by superimposing a graph showing the number of patients affected by KD on a graph showing the number of pollen grains dispersed during the same period. As a result, we confirmed that the year in which the number of patients with KD peaked coincided with the year in which the number of pollen grains dispersed peaked.
In 2003, we became convinced that there was a correlation between KD and the dispersal of pollen, and since then we have published four reports on the subject, stating that ‘pollen is probably the trigger factor for KD’. After that, the same method was used to examine Takayasu's disease, which is a vasculitis syndrome similar to KD, as well as 40 designated intractable diseases and 24 types of cancer and malignant tumors. As a result, we have reported eight papers that have revealed the correlation between the dynamics of the number of patients with the above diseases and the fluctuations in the number of pollen grains that were dispersed during the period from 1974 to 2015.
Akira AWAYA, Doctor of Medical Science（PhD）