Reduced mortality during the COVID-19 outbreak in Japan, 2020: a two-stage interrupted time-series design.

Koji Makiyama,Akifumi Eguchi,Yumi Kawamura,Yusuke Kobayashi,Kentaro Matsuura,Takuri Takahashi,Tomimasa Sunagawa,Shinya Uryu,Shoi Shi,Yuta Tanoue,Yuzo Arima,Masahiro Hashizume,Yuuki Tsuchihashi,Francesco Sera,Daisuke Onozuka,Daisuke Yoneoka,Takehiko I Hayashi ,Hiroaki Matsubara ,Shinichi Takayanagi,Takayuki Kawashima,Stuart Gilmour,Chris Fook Sheng Ng,Shuhei Nomura,Kazuhiko Kanou,Motoi Suzuki

doi:10.1093/ije/dyab216

Abstract

BackgroundCoronavirus disease 2019 (COVID-19) continues to be a major global health burden. This study aims to estimate the all-cause excess mortality occurring in the COVID-19 outbreak in Japan, 2020, by sex and age group.MethodsDaily time series of mortality for the period January 2015–December 2020 in all 47 prefectures of Japan were obtained from the Ministry of Health, Labour and Welfare, Japan. A two-stage interrupted time-series design was used to calculate excess mortality. In the first stage, we estimated excess mortality by prefecture using quasi-Poisson regression models in combination with distributed lag non-linear models, adjusting for seasonal and long-term variations, weather conditions and influenza activity. In the second stage, we used a random-effects multivariate meta-analysis to synthesize prefecture-specific estimates at the nationwide level.ResultsIn 2020, we estimated an all-cause excess mortality of −20 982 deaths [95% empirical confidence intervals (eCI): −38 367 to −5472] in Japan, which corresponded to a percentage excess of −1.7% (95% eCI: −3.1 to −0.5) relative to the expected value. Reduced deaths were observed for both sexes and in all age groups except those aged <60 and 70–79 years.ConclusionsAll-cause mortality during the COVID-19 outbreak in Japan in 2020 was decreased compared with a historical baseline. Further evaluation of cause-specific excess mortality is warranted.

Highlights

Since the early reports of an outbreak of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in Wuhan, China, in December 2019, coronavirus disease 2019 (COVID-19) has had global impact, resulting in considerable morbidity, mortality and economic burden.[1]
Our models revealed a decrease in mortality during the COVID-19 outbreak in February–December 2020 in Japan
Our findings showed that the COVID-19 outbreak may have potentially led to a decrease in deaths in Japan

Summary

Introduction

Since the early reports of an outbreak of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in Wuhan, China, in December 2019, coronavirus disease 2019 (COVID-19) has had global impact, resulting in considerable morbidity, mortality and economic burden.[1]. Few studies have accounted for weather factors, influenza epidemics, seasonality and long-term trends. These potential biases might affect interpretation of the results and resolving them requires quantification of excess mortality using more precise modelling methods. We estimated excess mortality by prefecture using quasiPoisson regression models in combination with distributed lag non-linear models, adjusting for seasonal and long-term variations, weather conditions and influenza activity.

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Conclusion