Clinical characteristics of COVID-19 in Osaka, Japan: Comparison of the first-third waves with the fourth wave

Background: The fourth wave of COVID-19 in Osaka Prefecture, Japan, caused a medical crisis. Here, we aim to identify the risk factors for COVID-19 severity and compare patients between the first-third waves and the fourth wave. Methods: We performed an observational retrospective study of COVID-19 cases at the National Hospital Organization Kinki-Chuo Chest Medical Center. Results: We identified 404 patients (median age: 71.0 years [interquartile range: 56.0-80.0]), of whom 199 (49.1%) had mild disease, 142 (35.2%) had moderate disease, and 63 (15.6%) had severe disease. The overall mortality rate was 5.4% (22/404). Based on multivariate logistic regression analysis, cardiovascular disease, fever, dyspnea, and several inflammatory biomarkers were independent risk factors for moderate to severe disease. For every 1 mg/dL increase in C-reactive protein, 10 IU/L increase in lactate dehydrogenase, and 100 ng/mL increase in ferritin, the risk for moderate to severe disease increased by 18.3%, 12.9%, and 8.9%, respectively. Overall disease severity in the fourth wave was higher than in the first-third waves. However, there was no significant difference in mortality. Because of a shortage of beds, four of the 28 severe patients (14.3%) in the fourth wave could not be transferred to the advanced hospital. Conclusions: Cardiovascular disease, fever, dyspnea, and several inflammatory biomarkers were risk factors for moderate to severe COVID-19 in our cohort. During the fourth wave, COVID-19 severity worsened, increasing the number of patients who could not be trans- ferred to beds for severe cases, resulting in a medical crisis in Osaka. (C) 2021 The Japanese Respiratory Society. Published by Elsevier B.V. All rights reserved.

Automated summary

The study identified cardiovascular disease, fever, dyspnea, and several inflammatory biomarkers as risk factors for moderate to severe COVID-19. Disease severity worsened in the fourth wave compared to the first three waves, resulting in a medical crisis in Osaka.