Trends in COVID-19 Risk-Adjusted Mortality Rates

Area of Science:

• Infectious Diseases
• Epidemiology
• Critical Care Medicine

Background:

• Early phases of the COVID-19 pandemic were associated with high in-hospital mortality rates.
• Recent observations suggest a decline in COVID-19 mortality, prompting investigation into contributing factors.
• Changes in patient demographics, including age and comorbidities, may influence observed mortality trends.

Purpose of the Study:

• To investigate the association between changing patient demographics and hospital mortality during the COVID-19 pandemic.
• To determine if the decrease in COVID-19 mortality rates is attributable to improved treatments or shifts in patient characteristics.
• To analyze in-hospital mortality trends adjusted for demographic and clinical factors within an academic health system.

Main Methods:

• Retrospective analysis of 5,121 hospitalizations for COVID-19 from March to August 2020 across three hospitals.
• In-hospital mortality or discharge to hospice was the primary outcome measure.
• Statistical adjustment for demographic factors, comorbidities, admission vital signs, and laboratory results was performed.

Main Results:

• Adjusted in-hospital mortality for COVID-19 decreased significantly from 25.6% in March to 7.6% in August 2020.
• The standardized mortality ratio declined from 1.26 in March to 0.38 in August, indicating a substantial reduction in observed versus expected deaths.
• The average probability of death decreased by 18.2 percentage points from March to August, after accounting for patient characteristics.

Conclusions:

• COVID-19 hospital mortality has demonstrably decreased within this academic health system.
• The observed reduction in mortality persists even after adjusting for changes in patient demographics and clinical profiles.
• These findings suggest a genuine improvement in COVID-19 outcomes over time, independent of patient population shifts.