Mortality in hospitalized older adults with COVID-19 during three waves: A multicenter retrospective cohort study

The waves of COVID-19 infections in Ontario, Canada, were marked by differences in patient characteristics and treatment. Our objectives were to (i) describe patient characteristics, treatment, and outcomes of hospitalized older adults with COVID-19 between waves 1, 2, and 3, (ii) determine if there was an improvement in in-hospital mortality in waves 2 and 3 after adjusting for covariates.

This retrospective cohort study was done in five acute care hospitals in Toronto, Ontario. Consecutive hospitalized older adults aged ≥65 years with confirmed COVID-19 infection were included. Wave 1 extended from March 11 to July 31, 2020, wave 2 from August 1, 2020 to February 20, 2021, and wave 3 from February 21 to June 30, 2021. Patient characteristics and outcomes were abstracted from charts. A logistic regression model was used to determine the association between COVID-19 and in-hospital mortality in waves 2 and 3 compared with wave 1.

Of the 1671 patients admitted to acute care, 297 (17.8%) were admitted in wave 1, 751 (44.9%) in wave 2, and 623 (37.3%) in wave 3. The median age of our cohort was 77.0 years (interquartile range: 71.0-85.0) and 775 (46.4%) were female. The prevalence of frailty declined in progressive waves. The use of dexamethasone, remdesivir, and tocilizumab was significantly higher in waves 2 and 3 compared with wave 1. In the unadjusted analysis, in-hospital mortality was unchanged between waves 1 and 2, but it was lower in wave 3 (18.3% vs. 27.4% in wave 1). After adjustment, in-hospital mortality was unchanged in waves 2 and 3 compared with wave 1.

In-hospital mortality in hospitalized older adults with COVID-19 was similar between waves 1 and 3. Further research should be done to determine if COVID-19 therapies have similar benefits for older adults compared with younger adults.