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Survival among people hospitalized with COVID-19 in Switzerland: a nationwide population-based analysis
Nanina Anderegg1,2, Radoslaw Panczak3, Matthias Egger3,4,5
1Institute of Social and Preventive Medicine, University of Bern, Bern, Switzerland. nanina.anderegg@ispm.unibe.ch.
Insights
COVID-19 survival rates improved over time. Survival decreased significantly when intensive care unit (ICU) occupancy exceeded 70%, highlighting the need for transmission control measures.
Area of Science:
- Epidemiology
- Public Health
- Critical Care Medicine
Background:
- Increasing age, male sex, and comorbidities are linked to lower survival rates in SARS-CoV-2 (COVID-19) patients.
- The complex interactions between these factors and their impact on survival, especially concerning intensive care unit (ICU) occupancy thresholds, remain incompletely understood.
Purpose of the Study:
- To analyze survival rates of hospitalized COVID-19 patients in Switzerland.
- To investigate the influence of epidemic wave, patient demographics (age, sex), comorbidities, and ICU occupancy on survival outcomes.
Main Methods:
- A national, population-based study of 22,648 hospitalized COVID-19 patients in Switzerland (Feb 2020 - Mar 2021).
- Bayesian survival models were employed to estimate survival, incorporating two-way interactions between age, sex, and comorbidities.
- ICU occupancy was analyzed using restricted cubic splines to detect non-linear associations with survival.
Main Results:
- Overall mortality was 21.1% (4785 deaths). Survival improved from the first to the second epidemic wave (76.1% vs. 80.5% at 40 days).
- Survival remained stable above 81.5% until ICU occupancy reached 70%, after which it declined (78.2% at 80% occupancy).
- Higher ICU occupancy (>70%) was associated with an estimated 137 excess deaths. Comorbidities impacted younger patients more severely; hypertension and obesity alone did not worsen survival, but hypertension combined with cardiovascular disease did.
Conclusions:
- COVID-19 survival has improved, likely due to better clinical management.
- A critical threshold of 70% national ICU occupancy was identified, beyond which survival significantly decreases.
- Proactive public health interventions to control SARS-CoV-2 transmission are crucial to prevent ICU overload and maintain patient survival rates.
Background:
Increasing age, male sex, and pre-existing comorbidities are associated with lower survival from SARS-CoV-2 infection. The interplay between different comorbidities, age, and sex is not fully understood, and it remains unclear if survival decreases linearly with higher ICU occupancy or if there is a threshold beyond which survival falls.
Method:
This national population-based study included 22,648 people who tested positive for SARS-CoV-2 infection and were hospitalized in Switzerland between February 24, 2020, and March 01, 2021. Bayesian survival models were used to estimate survival after positive SARS-CoV-2 test among people hospitalized with COVID-19 by epidemic wave, age, sex, comorbidities, and ICU occupancy. Two-way interactions between age, sex, and comorbidities were included to assess the differential risk of death across strata. ICU occupancy was modeled using restricted cubic splines to allow for a non-linear association with survival.
Results:
Of 22,648 people hospitalized with COVID-19, 4785 (21.1%) died. The survival was lower during the first epidemic wave than in the second (predicted survival at 40 days after positive test 76.1 versus 80.5%). During the second epidemic wave, occupancy among all available ICU beds in Switzerland varied between 51.7 and 78.8%. The estimated survival was stable at approximately 81.5% when ICU occupancy was below 70%, but worse when ICU occupancy exceeded this threshold (survival at 80% ICU occupancy: 78.2%; 95% credible interval [CrI] 76.1 to 80.1%). Periods with higher ICU occupancy (>70 vs 70%) were associated with an estimated number of 137 (95% CrI 27 to 242) excess deaths. Comorbid conditions reduced survival more in younger people than in older people. Among comorbid conditions, hypertension and obesity were not associated with poorer survival. Hypertension appeared to decrease survival in combination with cardiovascular disease.
Conclusions:
Survival after hospitalization with COVID-19 has improved over time, consistent with improved management of severe COVID-19. The decreased survival above 70% national ICU occupancy supports the need to introduce measures for prevention and control of SARS-CoV-2 transmission in the population well before ICUs are full.
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