“Even after risk adjustment for variety of clinical and demographic factors, including severity of illness at presentation, mortality was significantly and progressively lower over the course of the study period,” the study stated.
Patients of all ages experienced a decreased mortality rate. Among those, patients who were at or over the age of 75 saw the largest decrease, from just under 45 percent in the beginning of March to a under 10 percent in August.
A drive-thru Coronavirus COVID-19 testing station at a Kaiser Permanente facility in San Francisco, Calif., on March 12, 2020 (Justin Sullivan/Getty Images)
The study also suggests that the decreased mortality may be in part due to a combination of factors such as increased clinical experience, decreased hospital volume, as well as more advanced treatment procedures, something that was seen in another study conducted in the United Kingdom.
“There has been a substantial mortality improvement in people admitted to critical care with COVID-19 in England, with markedly lower mortality in people admitted in mid-April and May compared to earlier in the pandemic,” the study read.
As with Horwitz’s study, even after the adjustment made for the patient demographics, the decrease in mortality persisted, meaning that the demographic change isn’t likely the main cause of the mortality rate decrease.
“Possible causes include the introduction of effective treatments as part of clinical trials and a falling critical care burden,” the study read.
“I would classify this as a silver lining to what has been quite a hard time for many people. Clearly, there’s been something [that’s] gone on that’s improved the risk of individuals who go into these settings with COVID-19,” Mateen said.