STUDY AIMS: The COVID-19 pandemic required healthcare systems to reorganise around patient surges. Previous evidence associated these reorganisations with worse clinical outcomes for non-COVID-19 patients, to varying degrees. This exploratory study aimed to quantify the effects of successive COVID-19 waves on mortality, length of stay and transfers to intermediate and intensive care units among non-COVID-19 patients by comparing COVID-19 and non-COVID-19 periods in a Swiss hospital.

METHODS: This retrospective monocentric cohort study extracted electronic health data of patients hospitalised in a Swiss tertiary hospital from 1 January 2019 to 1 March 2023, whose primary discharge diagnosis was non-COVID-19, excluding patients from psychiatry and women-mother-child departments. Patients were then classified into COVID-19 wave periods based on the weekly average number of COVID admissions. Multivariable regressions were performed to compare in-hospital mortality, transfer rates to intermediate and intensive care units, and length of stay, adjusting for sex, age, insurance class, region of residence, level of care, Charlson comorbidity index, hospital department and main diagnosis.

RESULTS: A total of 22,972 non-COVID-19 patients hospitalised during three COVID-19 waves were included and compared to 51,252 pre-COVID-19 patients, 46,753 patients in the inter-wave period and 39,844 post-COVID-19 patients. Compared to the pre-COVID-19 period, adjusted in-hospital mortality among non-COVID-19 patients increased significantly during all COVID-19 waves, peaking in the first wave (OR: 1.27, 95% CI: 1.07–1.51), and decreased during inter-wave periods (OR: 0.91, 95% CI: 0.85–0.97). Transfers to intermediate care units increased throughout the COVID-19 period and normalised post-COVID-19, whereas transfers to intensive care units decreased significantly from the second wave onwards. Compared to the pre-COVID-19 period, length of stay did not differ during the first wave but was shorter in subsequent periods.

CONCLUSIONS: Worse outcomes among non-COVID-19 patients during COVID-19 waves highlight the need for protocols that ensure continuity and quality of care during future healthcare crises.