Why is COVID-19 fatal to obese people, even if young | Science

ScienceCOVID-19 report is supported by the Pulitzer Center and the Heising-Simons Foundation.

This spring, after a couple of days of flu-like symptoms and fever, a man arrived at the emergency room at the University of Vermont Medical Center. He was young and in his late thirties worshiping his wife and small children. And he was healthy and recording endless hours running his own small business. He is now positive for COVID-19 and is increasingly short of breath.

He was admitted directly to the intensive care unit (ICU) and was on a ventilator within hours. Two weeks later he died.

“He was a young, healthy, hard-working man,” recalls Mary Ellen Antkowiak, a lung emergency doctor, who is the ICU’s head of medicine at the hospital. “His main risk factor for this disease was obesity.”

Since the beginning of the pandemic, dozens of studies have reported that many of the most ill COVID-19 patients are obese. The link has been more clearly focused, as recent large-scale censuses have solidified the association in the last few weeks, showing that even those who are simply overweight are at higher risk. It was. For example, in the first meta-analysis of this kind published on August 26th, Obesity reviews, An international team of researchers pooled data from a number of peer-reviewed papers that included 399,000 patients. They are 113% more likely for obese people with SARS-CoV-2 to land at a hospital than for healthy weight, 74% more likely to be admitted to the ICU, and 48% more likely to die It has been discovered that

A collection of physiological and social factors drives these tough numbers. The biology of obesity includes immunodeficiency, chronic inflammation, and blood that is prone to thrombosis, all of which can exacerbate COVID-19. And obesity is so blamed that obese people may avoid medical care.

“We didn’t understand early on what the main risk factor was obesity….It was only recently that the devastating effects of obesity were noticed, especially in young people.” Said Andyxson, a doctor who studies obesity and lung disease at the University of Vermont. “It may be one reason for the devastating effects of COVID-19 in the United States, where 40% of adults are obese.”

Obese people are more likely than normal-weight people to have other conditions that are independent risk factors for severe COVID-19, such as heart disease, lung disease, and diabetes. In addition, you are more likely to have metabolic syndrome, and your blood sugar and/or fat levels may be unhealthy and your blood pressure may be high. A recent study from Tulane University in 287 hospitalized COVID-19 patients found that metabolic syndrome itself significantly increased the risk of ICU hospitalization, ventilation, and death.

However, with that alone, “BMI [body mass index] It remains a strong independent risk factor for severe COVID-19, according to several studies that adjusted for age, gender, social class, diabetes, and cardiac status,” said a specialist in cardiometabolic disorders at Glasgow University. Naveed Sattar says. “And it’s like a straight line.”

The impact extends to 32% of overweight people in the United States. The largest descriptive study of hospitalized US COVID-19 patients submitted as a preprint by Genentech researchers last month found that 77% of nearly 17,000 patients hospitalized with COVID-19 were overweight (29%). ) Or obesity (48%). (The US Centers for Disease Control and Management defines overweight as a BMI of 25 to 29.9 kilograms per square meter and obesity as a BMI of 30 or higher.)

Another study found COVID-19 hospitalization rates for more than 334,000 people in the UK. Published last month Minutes of the National Academy of Sciences, BMI peaked in people over 35, but found that as soon as someone turned to the overweight category, it started rising. “Many people aren’t aware they’re sneaking into that overweight category,” says Mark Hammer, the first author of exercise physiology at the University of London College.

The physical pathology that makes obese people vulnerable to severe COVID-19 begins with mechanics. Fat in the abdomen pushes the diaphragm up, and large muscles below the chest cavity hit the lungs, limiting airflow. This reduced lung volume leads to collapse of the airways in the lower lobes of the lungs, where more blood arrives due to oxygenation than in the upper lobes. “If you have already started [with] This discrepancy will make you worse from COVID-19,” said Dixon.

Other problems are exacerbating these mechanical problems. For starters, blood in obese people has an increased tendency to clot-in severe cases, independently, a particularly significant risk during infections. Clot small blood vessels in the lungs.. In healthy people, “the endothelial cells that line the blood vessels usually say “do not clot” in the surrounding blood,” says Beverley, a physician-scientist at Guy and St. Thomas, a specialist in blood clotting. Says Hunt. London hospital. However, “we believe COVID is altering signaling,” says Hunt. This is because the virus damages the endothelial cells, which respond to the damage and activate the coagulation system.

Adding obesity to the mix increases the risk of coagulation. In obese COVID-19 patients, Hunt says, “You have such sticky blood, oh-the most sticky blood you’ve ever seen in all of my years of practice. “.

Katherine Andersen, a nutritionist at Fairfield University, said that fat cells infiltrate the organs that produce and store immune cells, such as the spleen, bone marrow, and thymus, are also responsible for obese people. Immune power is also reduced. “We’re losing the immune system in exchange for adipose tissue, making the immune system less effective at protecting the body from pathogens and responding to vaccines,” she says.

The problem is not only the loss of immune cells, but the less effective cells, adds co-author Melinda Beck. Obesity reviews A meta-analysis studying obesity and immunity at the University of North Carolina at Chapel Hill. Beck’s study of how obese mice respond to the influenza virus has shown that the main immune cells, called T cells, “do not work as well in obesity,” she says. Fewer molecules help destroy the virus-infected cells, and the population of “memory” T cells that survived key infections to counteract future attacks by the same virus was less than healthy-weight mice. Will also be smaller.

Beck’s study suggests that the same thing happens to people: obese people vaccinated against influenza are found to be at twice the risk of healthy vaccinated people. did. This means that trials of the SARS-CoV-2 vaccine should include obese people, because “the coronavirus vaccine may be less effective in those people.”

Beyond impaired response to infections, obese people also suffer from mild, chronic inflammation. Adipocytes secrete several inflammation-inducing chemical messengers called cytokines, and more often come from immune cells called macrophages, which clear away dead and dying adipocytes. These effects may exacerbate the runaway cytokine activity that characterizes severe COVID-19. Ilhem Messaoudi, an immunologist who studies the host’s response to viral infections at the University of California, Irvine, says: At the risk of obesity, she adds:

The severity of COVID-19 in obese people helps explain the disproportionate toll of pandemics in some groups. For example, American Indians and Alaska Natives “have a very high obesity rate,” combined with poverty, lack of access to health foods, lack of health insurance, and opportunities for lack of exercise, says Pemvinachipewa, a public university in Colorado. Medical anthropologist in the Faculty of Hygiene. And obesity is “all these other [illnesses]Manson says he is more susceptible to severe COVID-19, including diabetes and cardiovascular disease.

In addition, according to a large body of literature, obese people can be blamed and may be delayed from receiving medical care due to the increased risk of severe illness and death. “Patients who experience weight prejudice are less likely to seek care and follow-up because they are unwelcome in the healthcare environment,” said Harvard Medical School and Obesity Physician at Massachusetts. Says Fatima Cody Stanford. general Hospital.

COVID-19 – She adds that there is an urgent need for specific research on this issue. “We don’t know how many people who never die in the community are dead,” says Stanford. “Maybe it’s [due] The two most common forms of stigma in the United States, depending on their weight and race.”

For people with obesity, the extra risk adds psychological burden, says Patinese, vice chair of the Obesity Behavior Alliance. “My anxiety is increasing completely,” she added, adding that she recently regained £30 of the £100 she had lost before the pandemic because of the stress-eating. “You have general anxiety about this pandemic… and you layer on it: “You, especially, you may really get sick.””

Data on how to treat obese COVID-19 patients are scarce. Published evidence supports giving such patients higher doses of anticoagulants, says Scott Kahan, a doctor of obesity medicine who directs the National Center for Weight and Wellness. However, little is known about whether and how other therapies are adjusted, such as lemdecibir and dexamethasone, also because obese patients are often “excluded from clinical trials.” Hmm. He strongly recommends that COVID-19 treatment trials include people with as high a BMI as possible.

Obese people should take special precautions to prevent getting sick, Messaudy said. “If you’re obese, you’ll be more cautious,” she says. “Wear your mask. Wash your hands. Avoid large gatherings.”

In addition, exercising and losing even a little weight can improve the metabolic health of obese people and, in doing so, reduce the chance of developing severe COVID-19 when infected. First, Stephen O’Rahilly says. Doctor scientist leading the MRC metabolic disease unit at the University of Cambridge. “For £300, losing a modest amount can result in a disproportionate amount of how well you can handle a coronavirus infection. You need to be a slim gym to benefit There is none.”