biostudies-literatureUnknownEndo HGovernment of Japan Ministry of Health Labour and WelfareJapan Society for the Promotion of Science<h4>Introduction</h4>Little information is available on the temporal trends in the clinical epidemiology and in-hospital mortality of patients with coronavirus disease 2019 (COVID-19) in Japan for waves 1, 2, and 3.<h4>Methods</h4>A national claims database was used to analyze the time trends in admission, medical procedure, and in-hospital mortality characteristics among patients with COVID-19. Patients who were ≥18 years and discharged from January 1, 2020 to February 28, 2021 were included.<h4>Results</h4>A multilevel logistic regression analysis of 51,252 patients revealed a decline in mortality in waves 2 and 3 (risk-adjusted mortality range = 2.17-4.07%; relative risk reduction = 23-59%; reference month of April 2020 = 5.32%). In the subgroup analysis, a decline in mortality was also observed in patients requiring oxygen support but not mechanical ventilation (risk-adjusted mortality range = 5.98-11.68%; relative risk reduction = 22-60%; reference month of April 2020 = 15.06%). Further adjustments for medical procedure changes in the entire study population revealed a decrease in mortality in waves 2 and 3 (risk-adjusted mortality range = 2.66-4.05%; relative risk reduction = 24-50%).<h4>Conclusions</h4>A decline in in-hospital mortality was observed in waves 2 and 3 after adjusting for patient/hospital-level characteristics and medical treatments. The reasons for this decline warrant further research to improve the outcomes of hospitalized patients.Journal of infection and chemotherapy : official journal of the Japan Society of ChemotherapyS1341-321X(22)00188-Xhttps://www.ebi.ac.uk/biostudies/studies/S-EPMC9239980biostudies-literatureTemporal trends in clinical characteristics and in-hospital mortality among patients with COVID-19 in Japan for waves 1, 2, and 3: A retrospective cohort study.PMC923998020AA2005Watanabe SFushimi KOhnuma TEndo HLee KfalseTemporal trends in clinical characteristics and in-hospital mortality among patients with COVID-19 in Japan for waves 1, 2, and 3: A retrospective cohort study.<h4>Introduction</h4>Little information is available on the temporal trends in the clinical epidemiology and in-hospital mortality of patients with coronavirus disease 2019 (COVID-19) in Japan for waves 1, 2, and 3.<h4>Methods</h4>A national claims database was used to analyze the time trends in admission, medical procedure, and in-hospital mortality characteristics among patients with COVID-19. Patients who were ≥18 years and discharged from January 1, 2020 to February 28, 2021 were included.<h4>Results</h4>A multilevel logistic regression analysis of 51,252 patients revealed a decline in mortality in waves 2 and 3 (risk-adjusted mortality range = 2.17-4.07%; relative risk reduction = 23-59%; reference month of April 2020 = 5.32%). In the subgroup analysis, a decline in mortality was also observed in patients requiring oxygen support but not mechanical ventilation (risk-adjusted mortality range = 5.98-11.68%; relative risk reduction = 22-60%; reference month of April 2020 = 15.06%). Further adjustments for medical procedure changes in the entire study population revealed a decrease in mortality in waves 2 and 3 (risk-adjusted mortality range = 2.66-4.05%; relative risk reduction = 24-50%).<h4>Conclusions</h4>A decline in in-hospital mortality was observed in waves 2 and 3 after adjusting for patient/hospital-level characteristics and medical treatments. The reasons for this decline warrant further research to improve the outcomes of hospitalized patients.2022-01-01T00:00:00Z2022 Jun2022-07-20T03:52:22.964Z2022-07-10T09:22:31.796ZS-EPMC92399803577980110.1016/j.jiac.2022.06.013