Obesity, metabolic syndrome tied to risk of COVID infection, severity

Overweight man's belly
Overweight man's belly

Mladen Zivkovic / iStock

Three new studies describe the link between obesity and elevated risk of COVID-19 infection and poor outcomes.

The first study, published yesterday in Diabetes Care, shows that predominantly black hospitalized COVID-19 patients with metabolic syndrome (a combination of obesity, high blood pressure, diabetes, and/or abnormal cholesterol levels that increases the risk of cardiovascular disease) were nearly five times more likely than their peers to require intensive care and a ventilator or experience respiratory distress and 3.4 times more likely to die from their infections.

The more of the metabolic syndrome diagnoses patients had, the worse their prognosis. While patients who had only one of the diagnoses weren't more likely than their peers to die, obesity and diabetes were tied to increased likelihood of needing intensive care and a ventilator. High blood pressure alone wasn't linked to any adverse outcome.

Increased need for vigilance

"The underlying inflammation that is seen with metabolic syndrome may be the driver that is leading to these more severe cases," lead author Joshua Denson, MD, MS, said in a Tulane University press release. "Metabolic syndrome should be considered a composite predictor of COVID-19 lethal outcome, increasing the odds of mortality by the combined effects of its individual components."

The researchers monitored 287 coronavirus patients hospitalized at two New Orleans hospitals from Mar 30 to Apr 5, which coincided with the pandemic peak in that city. Of the 287 patients, 188 (66%) had metabolic syndrome. Compared with their peers, a higher rate of patients with metabolic syndrome required care in an intensive care unit (ICU) (56% vs 24%), needed a ventilator (48% vs 18%), developed acute respiratory distress syndrome (37% vs 11%), and died (26% vs 10%).

Mean patient age was 61 years, nearly 57% were women, and more than 85% were black. Their most common underlying conditions were high blood pressure (80%), obesity (65%), diabetes (54%), and low levels of high-density lipoprotein ("good") cholesterol (39%).

Denson said in the press release that people with metabolic syndrome should be especially vigilant in avoiding exposure to COVID-19. "It doesn't matter if you're young or old—we took that into account," he said. "You really should be extra careful. I would say it should impact both preventing your exposures and, if you end up getting sick, you should probably see your doctor sooner."

Impaired ability to fight infection

The second study, a systematic review and meta-analysis of 75 Chinese- and English-language studies on obesity and COVID-19 published today in Obesity Reviews, found that obese people were at 1.5 times higher risk of coronavirus infection than their non-obese peers, 2.1 times more likely to be hospitalized for their infections, 1.7 times more likely to be admitted to an ICU, and 1.5 times more likely to die of the virus.

The researchers said that obesity-induced metabolic changes such as inflammation and impaired ability to use insulin can interfere with the ability to fight infections such as flu and hepatitis. Also, infection can lead to uncontrolled blood glucose in patients with diabetes, which can impair immune response.

"Individuals with obesity are also more likely to experience physical ailments that make fighting this disease harder, such as sleep apnea, which increases pulmonary hypertension, or a body mass index that increases difficulties in a hospital setting with intubation," coauthor Melinda Beck, PhD, of the University of North Carolina at Chapel Hill said in a university press release.

The authors said that they worry that a COVID-19 vaccine may be less effective in people with obesity, as is true for flu vaccine, which should be taken into account when vaccine candidates undergo testing. 

Lead author Barry Popkin, PhD, also of the University of North Carolina, said in the release that the pandemic has caused further slides in physical activity and the ability to access and pay for healthy foods.

"We're not only at home more and experience more stress due to the pandemic, but we're also not visiting the grocery store as often, which means the demand for highly processed junk foods and sugary beverages that are less expensive and more shelf-stable has increased," Popkin said. "These cheap, highly processed foods are high in sugar, sodium and saturated fat and laden with highly refined carbohydrates, which all increase the risk of not only excess weight gain but also key noncommunicable diseases."

He called for governments to implement strong public health policies to reduce the prevalence of obesity, such as warning labels on packaged foods high in sugar, fat, and salt, and limiting the marketing of unhealthy foods to children. "Given the significant threat COVID-19 represents to individuals with obesity, healthy food policies can play a supportive—and especially important—role in the mitigation of COVID-19 mortality and morbidity," Popkin said.

Higher risk of infection

In the third study, researchers in South Korea revealed that higher levels of obesity are associated with elevated risk of COVID-19 infection. Compared with healthy-weight control subjects, overweight adults were 1.1 times more likely to contract coronavirus, and obese people were 1.3 times more likely.

Published yesterday in Clinical Infectious Diseases, the case-control study of 3,788 COVD-19 patients and 15,152 matched controls from Jan 24 to Apr 9 showed that the association between obesity and elevated risk of infection held true even after adjustment for sociodemographic factors, the presence of underlying medical conditions, laboratory values, and the use of medications.

"As the COVID-19 pandemic evolves, continued investigation into the interplay between metabolic health, especially obesity, and the risk of COVID-19 is warranted in order to inform control strategies for COVID-19," the authors wrote. "While awaiting further evidence supporting causal relationship between obesity and the risk of COVID-19 infections, individuals with a higher [body mass index] could be potentially classified as high risk and thus, prioritized in COVID-19 testing."

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