Clinical Characteristics of COVID-19 in Nagano Prefecture : An Epidemiological Survey Including Data from Wave 1 to Wave 4

Purpose : This study aimed to evaluate the clinical characteristics of patients with coronavirus disease 2019 (COVID-19) hospitalized in the Nagano Prefecture during Waves 1-4 of the COVID-19 pandemic and identify the factors strongly associated with the duration of hospitalization and mortality using data from a database comprising hospital discharge summaries. Methods : In this retrospective study, we reviewed the database of Infection control measures department, Nagano Prefectural Government, utilizing medical records from 2,521 COVID-19 patients hospitalized during waves 1 and 4 (peaks in early April 2020 and May 2021). Risk factors for prolonged hospitalization and mortality risk were analysed using multivariate logistic regression. Results : The data of 76, 259, 1137, and 1049 patients hospitalized during Waves 1, 2, 3, and 4, respectively, were analyzed. The average age of the patients who died of COVID-19 was 86 years, with males accounting for the majority of cases. Old age, male sex, smoking history, and the presence of chronic heart failure (CHF) and chronic kidney disease (CKD) were associated with prolonged hospitalization. Old age and the presence of CKD showed significant associations with mortality. Conclusions : Patients with risk factors were older and had a prolonged duration of hospitalization, indicating that age and CKD are independent risk factors for prolonged hospitalization and mortality in patients with COVID-19 in the Nagano Prefecture. Preventing the incidence of COVID-19 in older patients and those with impaired renal function would shorten the hospitalization duration and improve prognosis.