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April 29, 2020 -- Jennifer Lighter, MD, a hospital epidemiologist in New York City, says within the first few days that she began treating COVID-19 patients in her hospital, she and other doctors quickly saw a pattern.

“I don’t think obese people are as prevalent in China compared to the U.S., so they didn’t have much data on this,” says Lighter, who works at New York University Langone Health. “But for us, it was very obvious and noticeable, even in those few first days, that there were a lot of young people in the ICU, and what stood out among the group of younger patients was their body weight. You couldn’t help but notice that they were all heavier-set.”

Lighter wanted to better understand if there really was a link between coronavirus and obesity, so she and Anna Stachel, assistant director of the Department of Infection Prevention and Control at NYU Langone Health, did a study of 3,615 patients under the age of 60 who tested positive for COVID-19. They found that body weight did not significantly raise the risk of hospitalization or more severe illness for people over 60. But it did in patients younger than 60, compared to those with a healthy body mass index, which is less than 30. The research showed:

  • Patients with a BMI of 30-34 were twice as likely to get admitted to the hospital or to be admitted to acute care.
  • Patients with a BMI of 35 or higher were twice as likely to be admitted to the hospital and three times as likely to end up in the intensive care unit.

“Patients who are obese are coming into the emergency department and presenting for medical care more because they are sicker. Once here, those with a higher BMI are also more likely to be admitted and more likely to end up in the ICU,” Lighter explains.

She says this is very important information for the U.S., since 42% of the American population has a BMI over 30 and is considered obese. “Our hospital was one of the first to find the association between obesity and coronavirus, but I think it will soon become very common,” Lighter says. “I expect every medical center in the U.S. will eventually see this.”

Data Is Piling Up

Leonardo Seoane, MD, is the chief academic officer, senior vice president, and pulmonary critical care doctor at Ochsner Health in New Orleans, which, like New York, has been an epicenter of this virus. He says over time, he and his colleagues began to see the connection between obesity and severe coronavirus symptoms in younger patients.

“We have an epidemic with obesity in the southern United States,” Seoane says. “Treating obese patients in the ICU is not new to us, so when we first started to get inundated with severely infected COVID patients ending up in the ICU, it didn’t necessarily raise an alarm for us because we typically take care of many obese patients in the ICU,” he explains. “In time, we started to realize this was different, though, as it became clear that the majority of the younger people in the ICU with coronavirus were obese.”

That inspired Seoane and the Ochsner Center for Outcomes and Health Services Research team to gather data. They studied 3,000 patients who tested positive for the coronavirus in his hospital system and found that 59% of the hospitalized patients were obese with an average BMI of 33. He says obesity nearly doubled the chances that patients with COVID-19 would end up in the ICU.

“When we looked at risk factors for ending up in the hospital and ICU, obesity was the leading risk factor other than age. And I think we were definitely surprised by that, as it has not been previously reported in the literature,” Seoane says. “There was a 71% increased risk of ending up in the ICU, with a range from 46% to 261% increased risk if you are obese. That’s a higher rate than the risk created by heart disease, diabetes, and even chronic lung disease.”

Seoane stresses that his data is not yet peer-reviewed but has been submitted to a top medical journal for review. Like Lighter, he believes this pattern will soon become evident at hospitals across the U.S.

Many other studies are finding similar results.

A second study out of NYU Langone Health of 4,103 COVID-19 patients found obesity was the second strongest predictor (after age) of hospitalization and progression to critical illness for those with the coronavirus disease -- even more so than lung disease, heart disease, and documented smoking history.

“This isn’t meant to scare people whose BMI is high,” says Christopher Petrilli, MD, a hospitalist at NYU Langone Health and the lead author of the study. “We aren’t saying everyone with a BMI over 30 is in danger. But we are saying they may be at higher risk of more severe symptoms and hospitalization than the general population, with everything else being held equal.”

Early research out of China finds obese COVID-19 patients have more than twice the risk of severe pneumonia than people of a lower weight.

While the link between obesity and more severe COVID-19 symptoms is becoming clear, researchers say they need more data to definitively say why. But there are several theories up for debate.

Some say it could be the simple mechanics of breathing. Extra weight puts an extra mechanical load on the lungs, chest, and diaphragm. That increases the effort involved in breathing and lowers the amount of oxygen in the lungs after a breath, which could lead to no reserve when you get an infection or injury to the lungs. Others think it could be that fat cells can cause inflammation, so when you have many of them, as obese patients do, that may lead to high inflammation, worsening the over-exuberant immune response to the virus seen in sepsis.

Why This Matters

Even as researchers continue to dig deeper into this topic, the question now is what to do with the information. Experts say in the short term, it’s important that front-line health care workers understand that obesity is becoming another high-risk category in relation to this virus.

“This knowledge should help front-line providers characterize which patients likely need a closer eye on them in terms of follow-up,” Petrilli says. “Our study is not saying only obese patients are hospitalized, require ventilation, intensive care, or that they die, but we do know there is a higher likelihood of those things.”

“The message for doctors and hospitals is: If you are assessing a patient and are on the fence between sending them home or admitting them into the hospital, you should lean towards bringing that patient into the hospital if they are obese because we know they have an increased chance of ending up in the ICU,” Seoane says. “In addition, doctors should be educating our patients that they are high-risk for developing severe complications from COVID-19 and should take extra precautions not to contract the disease.”

Experts agree that people do need to start using this newfound knowledge when making their own decisions about social distancing. “I think early on, a lot of Americans thought it was just the elderly that were at high risk. So I think it’s important that people understand that if they or a loved one is obese, that makes them high-risk, too, and they need to take extra precautions to make sure they don’t contract the virus,” Seoane says.

Show Sources

Jennifer Lighter, MD, NYU Langone Health, New York City.

Christopher Petrilli, MD, NYU Langone Health, New York City.

Leonardo Seoane, MD, Ochsner Health, New Orleans.

Clinical Infectious Diseases: “Obesity in patients younger than 60 years is a risk factor for Covid-19 hospital admission.”

medRxiv: “Factors associated with hospitalization and critical illness among 4,103 patients with Covid-19 disease in New York City.”

The Lancet: “Obesity and COVID-19 Severity in a Designated Hospital in Shenzhen, China.”

Obesity: “High prevalence of obesity in severe acute respiratory syndrome coronavirus‐2 (SARS‐CoV‐2) requiring invasive mechanical ventilation.”

CDC: “Adult Obesity Facts.”

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