A covid-19 patient is attached to a ventilator in the emergency room at St. Joseph's Hospital in Yonkers, N.Y., in April. (John Minchillo/AP)

Most elderly covid-19 patients put on ventilators at two New York hospitals did not survive, according to a sweeping study published Tuesday that captured the brutal nature of this new disease and the many ways it attacks the body.

The study, published in the Lancet, is broadly consistent with clinical findings from China and Europe, and confirmed that advanced age is the greatest risk factor for a severe outcome, particularly if accompanied by chronic underlying diseases, such as hypertension, diabetes, heart disease and obesity.

The high mortality rate, especially among elderly patients with some underlying disease, stunned Max O’Donnell, the senior author of the study and a pulmonologist at Columbia University Irving Medical Center.

“We had no idea how horrific this would be,” he said. “Definitely not just the flu.”

The research focused on 257 critically ill adults, representing a little under one-quarter of the confirmed coronavirus patients admitted at the two hospitals in northern Manhattan between March 2 and April 1. The median age of critically ill patients was 62 years, and two-thirds of them were male.

Of the critically ill patients studied, 39 percent had died by April 28, and 37 percent remained hospitalized at Milstein and Allen hospitals.

No critically ill patients under the age of 30 died at the two hospitals, O’Donnell said, and only a small number of them had to be put on ventilators. But more than 80 percent of people over 80 who went on a ventilator did not survive, he said.

Coronavirus may cause a shortage of ventilators, and U.S. health-care workers are worried there won't be enough of them to serve covid-19 patients. (Video: The Washington Post)

That fact, he said, should be shared with elderly patients and their family members when trying to decide whether to use the invasive procedure to treat severe illness associated with covid-19, the disease caused by the novel coronavirus.

“It’s a difficult conversation, obviously,” O’Donnell said.

Discharge and mortality rates for the most critically ill patients have varied widely among hospital systems. Doctors say the mortality rates — which range from 50 percent to 97 percent in published studies — probably reflect different regions’ demographics and the varied treatment practices in the early days of the outbreak, when doctors were writing and rewriting treatment protocols on the fly almost every day.

Early data from Northwell Health, New York state’s largest health system, for example, drew a grim picture of survival chances for patients who were ill enough to need mechanical ventilators. In a paper published April 22, doctors reported that of 1,281 critically ill patients, only 3.3 percent of them had been discharged, while 24.5 percent died. The rest remained hospitalized.

“The mortality rate [for patients on ventilators] creeps up to 70 percent when you’re over the age of 70,” Thomas McGinn, deputy physician in chief at Northwell Health, said Tuesday, noting that the new Lancet paper seems consistent with what his organization reported last month. “If your mom’s 85 and not well, they should know what the potential is for surviving before they have a ventilator placed.”

But at Emory Healthcare in Atlanta, 40 percent of the 217 critically ill patients made it to discharge while 29.7 percent died, according to data that has not yet been peer reviewed. Craig M. Coopersmith, a critical care doctor at Emory, said he feels the numbers show that “unequivocally, being on the ventilator is not a death sentence.”

The new Lancet paper adds details to the narrative of how patients fared during the catastrophic months of March and April, when hospitals in New York endured a surge of covid-19 cases.

The study appeared to confirm associations between a patient’s risk of death and markers for inflammation and coagulation in laboratory analyses of their blood samples. Doctors have been reporting in recent months that some covid-19 patients are suffering from clots that can lead to strokes or respiratory arrest.

The obesity rate is among the striking features of the new research: Among critically ill patients under the age of 50 who were admitted to the hospitals, 71 percent were obese.

Precisely how obesity plays a role in the disease is unclear, but the Lancet report notes that severe obesity — defined as a body mass index (BMI) over 40 — did not appear to increase the risk of death compared with the other critically ill patients. The authors of the report say further investigations are needed to understand whether obesity leads to greater susceptibility to coronavirus infection or to the kind of severe illness from covid-19 that leads to hospitalization.

Several other studies have highlighted obesity as a risk factor for severe covid-19, especially among patients younger than 60 years. According to one study published in the Clinical Infectious Diseases journal in early April, patients with a BMI over 30 were almost twice as likely to be admitted to a hospital with covid-19, and if their BMI was higher than 35, they were three times as likely to die as someone with a healthy BMI.

Jennifer L. Lighter, a hospital epidemiologist at NYU Langone who was the lead author on the Clinical Infectious Diseases study, said she believes different parts of the world have different vulnerabilities to the coronavirus. In China, she said, it was pollution and smoking. In Italy, the large older population and the fact that many live in multi-generational households contributed to mortality.

“In the United States, it’s obesity. That’s our Achilles’ heel when it comes to this virus,” Lighter said.

She said a number of theories may explain why obesity is implicated in amplifying the effects of the coronavirus. It could be because people who are obese are more likely to have compromised lung function to begin with and other issues that make them more vulnerable to a virus. They may also be more vulnerable to inflammation. It could also be that the virus attaches to something known as ACE receptors, which are highly expressed in fat cells. “So maybe the virus has more opportunities to attack,” she said.

The Lancet report found a high rate of problems not related to the respiratory system, notably kidney injury, evident in nearly a third of covid-19 patients and a clear signal that the novel coronavirus is distinct from influenza in the way it attacks multiple organs.

The Lancet study looked at hospitals that drew heavily from predominantly Hispanic and African American neighborhoods, and 62 percent of the critically ill patients were Hispanic. O’Donnell noted one racial and ethnic trend: White patients who are not Hispanic came to the hospital after three days of symptoms, on average, while Hispanics arrived after five days on average and African Americans after seven days.

“Part of this may speak to access to care,” O’Donnell said. When someone delays going to the hospital, he said, “you’re more likely to come in critically ill.”

Harlan Krumholz, a professor of medicine at Yale School of Medicine, said the Lancet study “gives a perspective on the devastating nature” of covid-19, and “should give pause to anyone who wants to dismiss SARS-CoV-2 as less than a major threat to health.”

Coronavirus: What you need to know

End of the public health emergency: The Biden administration ended the public health emergency for the coronavirus pandemic on May 11, just days after WHO said it would no longer classify the coronavirus pandemic as a public health emergency. Here’s what the end of the covid public health emergency means for you.

Tracking covid cases, deaths: Covid-19 was the fourth leading cause of death in the United States last year with covid deaths dropping 47 percent between 2021 and 2022. See the latest covid numbers in the U.S. and across the world.

The latest on coronavirus boosters: The FDA cleared the way for people who are at least 65 or immune-compromised to receive a second updated booster shot for the coronavirus. Here’s who should get the second covid booster and when.

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