October 22, 2020

Death rates for hospitalized Covid-19 patients have fallen sharply. What's driving the drop?

Daily Briefing

    Two new studies show that death rates among hospitalized Covid-19 patients have declined significantly—but while experts are celebrating the declines as evidence that new treatments and mitigation efforts are working, they're also warning that the drops don't mean Covid-19 is no longer a threat.

    Covid-19 guidance from clinicians at the forefront

    Covid-19 death rates decline

    For one of the studies, which was published preprint in August and will appear in the Journal of Hospital Medicine next week, researchers looked at more than 5,000 Covid-19 hospitalizations in the NYU Langone Health system that occurred between March and August. They found that, at the start of America's coronavirus epidemic, patients in the study had a 25.6% risk of dying. However, by the end of the study period, hospitalized Covid-19 patients' mortality risk dropped to 7.6%, the researchers found.

    The researchers then wanted to determine whether the drop in mortality risk was due to changes in the types of Covid-19 patients who were hospitalized throughout the study period.

    As Leora Horwitz, an author of the study who researches population health at New York University's Grossman School of Medicine, explained, "The people who are getting hospitalized now tend to be much younger, tend to have fewer other diseases, and tend to be less frail than people who were hospitalized in the early days of the epidemic." The researchers wanted to see whether that played a role in mortality risk as the epidemic persisted.

    To do so, the researchers adjusted their analyses of the hospitalization data for a variety of factors, including age and comorbidities such as diabetes. Ultimately, they discovered that Covid-19 death rates had dropped across all groups—including among older patients who typically are at higher risk of developing a severe case of and dying from Covid-19. According to the researchers, the death rate among older patients declined by 18 percentage points on average over the study period.

    For the second study, which also was published preprint but is slated to appear in the journal Critical Care Medicine, researchers looked at data on 21,000 hospitalized Covid-19 patients in England and discovered similar drops in mortality rates. Overall, the unadjusted death rate among patients involved in the study decreased by about 20 percentage points over the course of the study period.

    Why are Covid-19 death rates dropping?

    Health experts say it's likely that many factors have led to declines in Covid-19 mortality rates since the coronavirus pandemic's start. "All of the above is often the right answer in medicine, and I think that's the case here, too," Horwitz said.

    Two of those likely factors are that doctors now have better treatments for Covid-19 and they have more experience providing care to such patients, experts say.

    "In March and April, you got put on a breathing machine, and we asked your family if they wanted to enroll you into some different trials we were participating in, and we hoped for the best," Khalilah Gates, a critical care pulmonologist at Northwestern Memorial Hospital, said. "Six plus months into this, we kind of have a rhythm, and so [Covid-19 patients have] become an everyday standard patient for us at this point in time."

    As the epidemic has persisted, doctors have improved their ability to recognize when a Covid-19 patient is at risk of a blood clot or so-called "cytokine storm," Amesh Adalja—an infectious disease, critical care, and emergency medicine physician at the Johns Hopkins Center for Health Security—said.

    In addition, doctors now have standardized Covid-19 treatments developed by groups such as the Infectious Diseases Society of America, Adalja said.

    "We know that when people are getting standardized treatment, it makes it much easier to deal with the complications that occur because you already have protocols in place," Adalja explained. "And that's definitely what's happened in many hospitals around the country."

    Horwitz and Bilal Mateen, a data science fellow at the Alan Turing Institute and an author of the England study, said factors outside of physicians' control also may be linked to the declining death rates.

    Horwitz, for example, said she believes mask-wearing likely has played a part, because wearing masks can help to lessen the viral load of the novel coronavirus to which a person is exposed. That, in turn, can reduce their chance of developing severe Covid-19, Horwitz said.

    And Mateen said his study suggests that, because hospitals later in the pandemic were able to stay below their maximum capacities, they were able to provide better care to Covid-19 patients. Mateen said that, when hospitals see a surge in Covid-19 cases, "staff are stretched, mistakes are made, [and] it's no one's fault—it's that the system isn't built to operate near 100%."

    Experts preach caution

    But while declines in Covid-19 death rates are good news, experts still caution that Covid-19 is a very serious disease.

    For instance, a CDC study released this week found that hospitalized Covid-19 patients within the Veterans Health Administration (VHA) were five times more likely to die than hospitalized patients within VHA who had the flu. In addition, the hospitalized Covid-19 patients had a higher risk of developing 17 complications than the hospitalized flu patients.

    Horwitz noted that while the Covid-19 death rate in the study she worked on declined to 7.6%, which marked a significant improvement, that number "is still higher than many infectious diseases, including the flu."

    Further, Horwitz added that patients who recover from Covid-19 can experience long-lasting complications. Covid-19 "still has the potential to be very harmful in terms of long-term consequences for many people," she said.

    Gates also emphasized the potential long-term consequences of Covid-19. "A lot of my patients are still complaining of shortness of breath," she said. "Some of them have persistent changes on their CT scans and impacts on their lung functions."

    Overall, Horwitz said that while the recent findings are encouraging, they do not mean Covid-19 is "a benign illness" (Brumfiel, "Shots," NPR, 10/20; Owens, "Vitals," Axios, 10/21).

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