Kristoffer Strålin1,2,3, Erik Wahlström4, Sten Walther5,6,7, Anna M Bennet-Bark4, Mona Heurgren4, Thomas Lindén8, Johanna Holm4, Håkan Hanberger9,10. 1. Department of Infectious Diseases, Karolinska University Hospital, Stockholm, Sweden. 2. Department of Medicine, Huddinge, Karolinska Institute, Stockholm, Sweden. 3. Infectious Diseases Section, National Programme for Evidence-based Healthcare Management: Sweden's Regions in Collaboration, Stockholm, Sweden. 4. Department of Registers and Statistics, National Board of Health and Welfare, Stockholm, Sweden. 5. Swedish Intensive Care Register, Värmland County Council, Karlstad, Sweden. 6. Department of Cardiothoracic and Vascular Surgery, Heart Centre, Linköping University Hospital, Linköping, Sweden. 7. Department of Health, Medicine, and Caring Sciences, Faculty of Medicine and Health Sciences, Linköping University, Linköping, Sweden. 8. Department for Knowledge-Based Policy of Health Care, National Board of Health and Welfare, Stockholm, Sweden. 9. Department of Biomedical and Clinical Sciences, Division of Inflammation and Infection, Faculty of Medicine and Health Sciences, Linköping University, Linköping, Sweden. 10. Department of Infectious Diseases, Linköping University Hospital, Linköping, Sweden.
Abstract
INTRODUCTION: Studies from the first pandemic wave found associations between COVID-19 hospital load and mortality. Here, we aimed to study if mortality of hospitalized COVID-19 patients was associated with the COVID-19 admission rate during a full year of the pandemic in Sweden. METHOD: Observational review of all patients admitted to hospital with COVID-19 in Sweden between March 2020 and February 2021 (n = 42,017). Primary outcome was 60-day all-cause mortality related to number of COVID-19 hospital admissions per month/100,000 inhabitants. Poisson regression was used to estimate the relative risk for death by month of admission, adjusting for pre-existing factors. RESULTS: The overall mortality was 17.4%. Excluding March 2020, mortality was clearly correlated to the number of COVID-19 admissions per month (coefficient of correlation ρ=.96; p<.0001). After adjustment for pre-existing factors, the correlation remained significant (ρ=.75, p=.02). Patients admitted in December (high admission rate and high mortality) had more comorbidities and longer hospital stays, and patients treated in intensive care units (ICU) had longer pre-ICU hospital stays and worse respiratory status on ICU admission than those admitted in July to September (low admission rate and low mortality). CONCLUSION: Mortality in hospitalized COVID-19 patients was clearly associated with the COVID-19 admission rate. Admission of healthier patients between pandemic waves and delayed ICU care during wave peaks could contribute to this pattern. The study supports measures to flatten-the-curve to reduce the number of COVID-19 patients admitted to hospital.
INTRODUCTION: Studies from the first pandemic wave found associations between COVID-19 hospital load and mortality. Here, we aimed to study if mortality of hospitalized COVID-19 patients was associated with the COVID-19 admission rate during a full year of the pandemic in Sweden. METHOD: Observational review of all patients admitted to hospital with COVID-19 in Sweden between March 2020 and February 2021 (n = 42,017). Primary outcome was 60-day all-cause mortality related to number of COVID-19 hospital admissions per month/100,000 inhabitants. Poisson regression was used to estimate the relative risk for death by month of admission, adjusting for pre-existing factors. RESULTS: The overall mortality was 17.4%. Excluding March 2020, mortality was clearly correlated to the number of COVID-19 admissions per month (coefficient of correlation ρ=.96; p<.0001). After adjustment for pre-existing factors, the correlation remained significant (ρ=.75, p=.02). Patients admitted in December (high admission rate and high mortality) had more comorbidities and longer hospital stays, and patients treated in intensive care units (ICU) had longer pre-ICU hospital stays and worse respiratory status on ICU admission than those admitted in July to September (low admission rate and low mortality). CONCLUSION: Mortality in hospitalized COVID-19 patients was clearly associated with the COVID-19 admission rate. Admission of healthier patients between pandemic waves and delayed ICU care during wave peaks could contribute to this pattern. The study supports measures to flatten-the-curve to reduce the number of COVID-19 patients admitted to hospital.