COVID-19 mortality rate drops significantly in Sweden

A new observational study by Swedish researchers shows a significant reduction in mortality in hospitalized patients infected with Severe Acute Respiratory Syndrome coronavirus 2 (SARS-CoV-2). Their study, entitled “Reducing Mortality in Hospitalized Covid-19 Patients in Sweden: A National Observational Study,” was released online as a preprint. To medRxiv*server.

Background

The new coronavirus SARS CoV-2, which causes coronavirus disease (COVID-19), infects more than 44 million people worldwide and kills more than 1.17 million people. Most COVID cases are hospitalized for complications caused by infection.

Researchers write that the enormous capacity of the virus to infect outbreaks and spread rapidly puts a great deal of pressure on general health systems, especially hospitals. The mortality rate of people admitted to hospitals with COVID is over 20%. 34% of patients require intensive care. The team writes that the percentage of patients requiring ICU admission is between 17 and 32 percent. These figures are from a survey conducted between February and April 2020. Over time, the understanding of infection and its management has improved, and thus survival has also improved over time.

The new study, conducted in Swedish patients, confirmed whether there was a change in the mortality rate of inpatient COVID-19 patients nationwide. Researchers have found that 60-day mortality (defined as death from any cause within 60 days of index admission), mortality in COVID-19 patients, both untreated and ICU-treated. I tried to confirm in the first 4 months. Pandemic. The data is from the Swedish National Health and Welfare Commission (NBHW).

Study design

This was a national observational cohort study of patients admitted to Sweden.^st March and 30th^th June 2020. From 14 days to 5 days after admission, all patients tested positive for SARS-CoV-2 RNA. The code for their discharge was COVID-19. All Swedish hospitals were included in the study.

A total of 15,761 COVID-19 inpatients were included in the study. The data is from the Swedish National Health and Welfare Commission. A 60-day all-cause mortality rate for patients was recorded and analyzed. Patient populations were categorized according to month of admission. The relative risk of patient death for each month of hospitalization was calculated. Factors such as existing comorbidities, age, gender and care dependence, and serious illness were considered.

Simplified Acute Physiology, version 3 (SAPS3), and oxygenation index (PaO2 / FiO2) were used among patients admitted to the ICU to assess the severity of the disease. The treatments and procedures they received in the ICU were also recorded.

What did you find?

The overall results of the study can be summarized as follows:

• A total of 15,761 patients were hospitalized.
• The median age of patients was 64 years (between 51 and 78 years), of which 57.5 percent were male.
• The highest number of visitors was in April 2020
• The overall proportion of patients admitted to the ICU was 14.4 percent.
• The age distribution of inpatients changed over time, with the number of patients under 40 and over 90 increasing between March and June.

• The overall cause 60-day mortality rate for Swedish patients admitted with COVID-19 was 17.8% (17.2 to 18.4%).
• The mortality rate in March 2020 was 24.7, but dropped to 13.3% in June 2020.
• The adjusted relative risk (RR) for June mortality was 0.56 (95% CI, 0.51 to 0.63), using the March rate as the baseline.
• Relative mortality risk for non-ICU patients was 0.60 (95% CI, 0.53 to 0.67) and 0.61 (95% CI, 0.48 to 0.79), respectively, compared to patients admitted to the ICU.
• Enrollment rates in ICU dropped from 19.5 percent (95 percent CI, 17.9 percent to 21.0 percent) in March to 11.0 percent (95 percent CI, 9.9 percent to 12.2 percent) in June 2020.
• In June, the proportion of ICU inpatients receiving mechanical ventilation decreased from 86.5% in March to 58.6%.
• In June, the proportion of ICU inpatients undergoing dialysis decreased from 22.8% in March to 13.8%.
• SAP S3 and PaO2 / FiO2 upon admission to the ICU were similar among patients throughout the study.

Conclusions and implications

The study reveals that the mortality rate of hospitalized Swedish COVID-19 patients declines with the duration of the pandemic. This reduction is independent of existing comorbidities among patients. The authors are seeking further research to understand the reasons behind this decline. The authors write that “changing covid-19 mortality should be taken into account when managing and assessing the outcome of studies from the first pandemic wave.”

*Important Notices

medRxiv Publish preliminary scientific reports that should not be considered definitive as they have not been peer-reviewed, guide clinical practice / health-related behaviors, and should not be treated as established information.