Risk factors for severity on admission and the disease progression during hospitalization in a large cohort of COVID-19 patients in Japan
Authors: Terada Mari , Ohtsu Hiroshi , Saito Sho , Hayakawa Kayoko , Tsuzuki Shinya , Asai Yusuke , Matsunaga Nobuaki , Kutsuna Satoshi , Sugiura Wataru , Ohmagari Norio 
Published: April 2021

AbstractObjectivesTo investigate the risk factors contributing to severity on admission. Additionally, risk factors on worst severity and fatality were studied. Moreover, factors were compared based on three points: early severity, worst severity, and fatality.DesignA observational cohort study utilizing data entered in a Japan nationwide COVID-19 inpatient registry, COVIREGI-JP.SettingAs of August 31, 2020, 7,546 cases from 780 facilities have been registered. Participating facilities cover a wide range of hospitals where COVID-19 patients are admitted in Japan.ParticipantsParticipants who had a positive test result on any applicable SARS-CoV-2 diagnostic tests, and were admitted to participating healthcare facilities. A total of 3,829 cases were identified from January 16 to May 31, 2020, of which 3,376 cases were included in this study.Primary and secondary outcoe measuresPrimary outcome was severe or non-severe on admission, determined by the requirement of mechanical ventilation or oxygen therapy, SpO2, or respiratory rate. Secondary outcome was the worst severity during hospitalization, judged by the requirement of oxygen and/or IMV/ECMO.ResultsRisk factors for severity on admission were older age, male, cardiovascular disease, chronic respiratory disease, diabetes, obesity, and hypertension. Cerebrovascular disease, liver disease, renal disease or dialysis, solid tumor, and hyperlipidemia did not influence severity on admission; however it influenced worst severity. Fatality rates for obesity, hypertension, and hyperlipidemia were relatively lower.ConclusionsThis study segregated the comorbidities driving severity and death. It is possible that risk factors for severity on admission, worst severity, and fatality are not consistent and may be propelled by different factors. Specifically, while hypertension, hyperlipidemia, and obesity had major effect on worst severity, their impact was mild on fatality in the Japanese population. Some studies contradict our results; therefore, detailed analyses, considering in-hospital treatments, are needed for validation.Trial registrationUMIN000039873. https://upload.umin.ac.jp/cgi-open-bin/ctr_e/ctr_view.cgi?recptno=R000045453Strengths and limitations of this studyIn this article, we studied the disease progression of COVID-19, by comparing the risk factors on three points: early severity, worst severity, and fatality.Our results are useful from a public health perspective, as we provide risk factors for predicting the severity on admission and disease progression from patients’ background factors.This study pointed out the possibility that risk factors of the severity on admission, worst severity, and fatality are not consistent and may be propelled by different factors.Our data were collected from hundreds of healthcare facilities; thus data accuracy may be questionable.Also, treatment type, dosage, duration, and combination varied immensely across the facilities and we did not consider treatments prior to and during hospitalization in the analysis.