2026 年 9 巻 4 号 p. 887-899
Introduction: Quantifying the impact of coronavirus disease (COVID) 2019 (COVID-19) on mortality has become increasingly challenging in the Omicron-variant era. This difficulty arises from reduced excess mortality, the presence of long COVID, and the lack of a strict definition of COVID-19-related death, which has led to inconsistencies in reported mortality rates. Accurate cause-of-death statistics are essential for health care policymaking.
Methods: We conducted a retrospective cohort study in patients aged ≥65 years who were admitted to the COVID-19 isolation ward of our hospital between July 1, 2021 and September 30, 2023. The primary outcome was survival to hospital discharge. Causes of death were classified according to the World Health Organization definition into four categories: COVID-19, COVID-19-associated complications, pre-COVID-19 medical conditions, and post-COVID-19 complications. The latter two categories were considered deaths unrelated to COVID-19.
Results: A total of 182 patients with mild or moderate COVID-19 were included for analysis. Among these, 23 (13%) died during hospitalization. Those who died were more likely to have moderate COVID-19, impaired physical or eating functions, and multiple comorbidities than were survivors. Of the 23 deaths, only 8 (35%) were attributed to COVID-19 or COVID-19-associated complications, whereas 15 (65%) were due to pre-COVID-19 medical conditions or post-COVID-19 complications. Concordance between Japanese public criteria for COVID-19-related death and our classification method was low (Cohen's κ = 0.223).
Conclusions: In this cohort of older patients with mild or moderate COVID-19, in-hospital mortality was relatively high. However, most deaths were not directly attributable to COVID-19. Larger studies are needed to further clarify mortality outcomes in this population.
