Advance Publication by J-STAGE Journal of Epidemiology Letter to the Editor J Epidemiol 2021 Excess All-Cause Mortality During the COVID-19 Outbreak in Japan Takashi Yorifuji, Naomi Matsumoto, and Soshi Takao Department of Epidemiology, Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University, Okayama, Japan Received October 15, 2020; accepted October 20, 2020; released online October 31, 2020 Copyright © 2020 Takashi Yorifuji et al. This is an open access article distributed under the terms of Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Dear Sir was identified in January, and the number of patients peaked in The outbreak of coronavirus disease 2019 (COVID-19) began in mid-April and in July (Figure 1). The excess mortality (number) Wuhan, China, in December 2019, and is now a global was positive only in April (about 2,000 excess deaths), but was pandemic.1 COVID-19 has placed a huge burden on population negative for the other months during the study period. Prefectures health. One of the indicators used to assess the impact is excess with a higher COVID-19 incidence tended to have an increased mortality. Excess mortality includes mortality of people excess mortality rate (r = 0.43); however, there was a negative diagnosed with COVID-19, those infected with COVID-19 but excess mortality rate in all except two prefectures (Figure 2). undiagnosed, and those who were not infected with COVID-19 These results demonstrate that excess mortality in Japan but died from social changes caused by the pandemic. Marked occurred only in April 2020 (at the first peak of the COVID-19 excess mortality has already been reported in the US and outbreak). In contrast, the numbers were negative in the other Europe.2–4 Japan is also experiencing a COVID-19 outbreak, but assessed months. Overall, therefore, net mortality decreased the impact seems to be minimal (1,601 deaths in a population of during the study period compared with the previous 2 years (2018 126 million as of 6th October 2020).5 Assessment of excess and 2019). Moreover, although there was a positive prefecture- mortality may enable more detailed evaluation of the impact of level relationship between cumulative COVID-19 incidence and COVID-19. Here, we evaluated the excess mortality during the excess mortality rate, most prefectures had a negative excess COVID-19 epidemic in Japan. mortality rate. We obtained the cause-specific cumulative number The study period was from January 2020, when the of mortalities from January to May in Japan (2018–2020), when Government strengthened public health regulations such as hand the latest cause-specific mortality data were available, from the washing against infections including COVID-19, to July 2020, Monthly Vital Statistics Report from the Ministry of Health, when the latest mortality data were available. We obtained the Labour and Welfare in Japan. We then show the percent change number of patients with COVID-19 per day in Japan, the relative to the number of deaths in 2018 in each year separated cumulative number of patients with COVID-19 by prefecture up by selected causes of death (Figure 3). This figure shows that to 31st July 2020, and mortality data (2018–2020) from the the decreased monthly and net mortality are partly explained by Prompt Vital Statistics Report from the Ministry of Health, decreased mortality related to infection, including influenza6 or Labour and Welfare in Japan. pneumonia, owing to the reduced transmission risk, accidents The monthly all-cause excess mortality (number) from January possibly due to the lower social activity,7 or circulatory diseases. to July 2020 was estimated by subtracting the expected monthly Although a limitation of our study is that we did not consider mortality (mean monthly mortality in 2018 and 2019) from the excess mortality during the second wave of COVID-19 infections observed mortality of the corresponding month in 2020. We in July=August 2020, the results suggest that public health then plotted the monthly excess mortality with the number of regulations aimed at preventing COVID-19 may incidentally patients with COVID-19 per day in Japan. We also evaluated the reduce mortality related to influenza and other infections or other prefectural-level association between the cumulative incidence causes and consequently contribute to reduced net mortality. of patients with COVID-19 up to July 2020 and the excess mortality rate from January to July 2020. We used the population estimation in October 2019 from the Statistic Bureau of Japan ACKNOWLEDGMENTS to calculate the cumulative incidence and excess mortality rate. We appreciate Saori Irie for her valuable support in collecting the We calculated the correlation coefficient using Stata 16 data. We thank Kelly Zammit, BVSc, from Edanz Group (https:== (StataCorp, College Station, TX, USA). Ethical approval was en-author-services.edanzgroup.com=ac) for editing a draft of this not obtained because we used aggregate data from publicly manuscript. available sources. Authors’ contributions: TY analyzed the data and wrote the There were 132,622, 117,010, 119,161, 113,362, 108,380, first draft, NM and ST contributed to the interpretation of the data 100,423, and 104,849 total deaths per month in Japan from and revised the manuscript. All authors read and approved the January to July 2020. The first patient in Japan with COVID-19 final draft. Address for correspondence. Takashi Yorifuji, Department of Epidemiology, Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University, 2-5-1 Shikata-cho, Kita-ku, Okayama 700-8558, Japan (e-mail: [email protected]). DOI https://doi.org/10.2188/jea.JE20200492 HOMEPAGE http://jeaweb.jp/english/journal/index.html JE20200492-1 COVID-19 and Excess Mortality in Japan Number of patients Excess mortality (number) (number) 1800 4000 1600 2000 1400 1200 0 1000 -2000 800 600 -4000 400 -6000 200 0 -8000 16-Jan-20 16-Feb-20 16-Mar-20 16-Apr-20 16-May-20 16-Jun-20 16-Jul-20 Figure 1. Daily number of patients with COVID-19 and monthly excess mortality in Japan ( ). Excess mortality rate (per 1000) 0.2 0.1 0 -0.1 -0.2 -0.3 -0.4 -0.5 -0.6 0 0.10.20.30.40.50.60.70.80.91 Cumulative incidence (per 1000) Figure 2. Cumulative number of patients with COVID-19 in Japan until July 2020, and excess mortality from January to July 2020 in each prefecture. 2 j J Epidemiol 2021 Yorifuji T, et al. 2019 2020 (%) 2018 100 80 60 40 20 0 All causes Certain infectious Neoplams Diseases of the Diseases of the Influenza Pneumonia Injury, poisoning, and parasitic (C00-D48) circulatory respiratory (J10-J11) (J12-J18) and certain other diseases system system consequences of (A00-B99) (I00-I99) (J00-J98) external causes Number of (V01-Y89) deaths in (n=594,102) (n=10,589) (n=159,218) (n=160,944) (n=87,691) (n=3,165) (n=43,995) (n=30,707) 2018 Figure 3. Percent change relative to cumulative number of mortality from January to May in 2018 separated by selected causes of death during the period from 2018 to 2020 in Japan. ICD-10 (International Classification of Diseases 10th Revision) codes are shown in the parentheses. Numbers of deaths from January to May in 2018 are also shown in the bottom. Source of funding: The present study was supported by grant during the COVID-19 outbreak - New York City, March 11–May 2, no. 7402000035 from Okayama Prefecture for the COVID-19 2020. MMWR Morb Mortal Wkly Rep. 2020;69(19):603–605. outbreak investigation. 4. Vestergaard LS, Nielsen J, Richter L, et al. Excess all-cause mortality fl during the COVID-19 pandemic in Europe - preliminary pooled Con icts of interest: None declared. estimates from the EuroMOMO network, March to April 2020. Euro Surveill. 2020;25(26). 5. Ministry of Health Labour and Welfare in Japan. About Corona- REFERENCES virus Disease 2019 (COVID-19). https:== www.mhlw.go.jp=stf= 1. World Health Organization. Coronavirus disease (COVID-19) pan- seisakunitsuite=bunya=newpage_00032.html Accessed October 7, demic. https:== www.who.int=emergencies=diseases=novel-coronavirus- 2020. 2019 Accessed October 7, 2020. 6. Sakamoto H, Ishikane M, Ueda P. Seasonal influenza activity during 2. Fouillet A, Pontais I, Caserio-Schönemann C. Excess all-cause the SARS-CoV-2 outbreak in Japan. JAMA. 2020;323(19):1969– mortality during the first wave of the COVID-19 epidemic in France, 1971. March to May 2020. Euro Surveill. 2020;25(34). 7. National Police Academy in Japan. Statistics about Road Traffic. 3. New York City Department of Health and Mental Hygiene (DOHMH) http:== www.npa.go.jp=publications=statistics=koutsuu=index_jiko.html COVID-19 Response Team. Preliminary estimate of excess mortality Accessed October 7, 2020. J Epidemiol 2021 j 3.