CDC Data Strengthens Link Between Obesity and Severe COVID

Damian McNamara

March 08, 2021

Updated March 10, 2021 // Editor's note: This story was updated with comments from the report's lead author and a commenting physician.

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Officials have previously linked being overweight or obese to a greater risk for more severe COVID-19. A report today from the US Centers for Disease Control and Prevention adds numbers and some nuance to the association.

Data from nearly 150,000 US adults hospitalized with COVID-19 nationwide indicate that risk for more severe disease outcomes increases along with body mass index (BMI). The risk of COVID-19-related hospitalization and death associated with obesity was particularly high among people younger than 65.

"One surprising result was that more than half, 50.8%, of the adult patients with COVID-19 in our study had obesity, compared to 42.4% nationally," lead author Lyudmyla Kompaniyets, PhD, told Medscape Medical News. "This suggests that adults with COVID-19 and obesity might commonly receive care in emergency departments or hospital settings.

"Additionally, in contrast to previous studies that demonstrated little or no association between obesity and COVID-19 severity among older patients, this large study of 238 hospitals did find that overweight and obesity were risk factors for invasive mechanical ventilation," said Kompaniyets, a researcher in the Division of Nutrition, Physical Activity, and Obesity at the CDC's National Center for Chronic Disease Prevention and Health Promotion.

A novel finding of this report is that obesity was also a risk factor for hospitalization and death among patients aged 65 and older, she added.

"As clinicians develop care plans for COVID-19 patients, they should consider the risk for severe outcomes in patients with higher BMIs, especially for those with severe obesity," the researchers note. They add their findings suggest "progressively intensive management of COVID-19 might be needed for patients with more severe obesity."

People with COVID-19 close to the border between a healthy and overweight BMI — from 23.7 kg/m2 to 25.9 kg/m2 — had the lowest risks for adverse outcomes.

The study was published online today in Morbidity and Mortality Weekly Report.

Greater Need for Critical Care

The risk of ICU admission was particularly associated with severe obesity. For example, those with a BMI in the 40 to 44.9 kg/m2 category had a 6% increased risk, which jumped to 16% higher among those with a BMI of 45 or greater.

Compared to people with a healthy BMI, the need for invasive mechanical ventilation was 12% more likely among overweight adults with a BMI of 25 to 29.2. The risked jumped to 108% greater among the most obese people, those with a BMI of 45 or greater, lead CDC researcher Lyudmyla Kompaniyets, PhD, and colleagues reported.

Moreover, the risks for hospitalization and death increased in a dose-response relationship with obesity.

For example, risks of being hospitalized were 7% greater for adults with a BMI between 30 to 34.9 and climbed to 33% greater for those with a BMI of 45. Risks were calculated as adjusted relative risks compared to people with a healthy BMI between 18.5 and 24.9.

Interestingly, being underweight was associated with elevated risk for COVID-19 hospitalization as well. For example, people with a BMI of less than 18.5 had a 20% greater chance of admission vs people in the healthy BMI range. Unknown underlying medical conditions or issues related to nutrition or immune function could be contributing factors, the researchers note.

Elevated Risk of Dying

The risk of death in adults with obesity ranged from 8% higher in the 30 to 34.9 range up to 61% greater for those with a BMI of 45.

Chronic inflammation or impaired lung function from excess weight are possible reasons that higher BMI imparts greater risk, the researchers note.

The CDC researchers evaluated 148,494 adults from 238 hospitals participating in PHD-SR database. Because the study was limited to people hospitalized with COVID-19, the findings may not apply to all adults with COVID-19.

Another potential limitation is investigators were unable to calculate BMI for all patients in the database because about 28% of participating hospitals did not report height and weight.

"The study reconfirms the important relationship between obesity and the worsening of COVID-19," said Lee Kaplan, MD, PhD, director of the Obesity, Metabolism and Nutrition Institute at Massachusetts General Hospital, Boston.

"It is clear from our own data at Mass General that risks of ICU stay and ventilation are higher in people with obesity," he added.

Although other research indicates obesity does not increase the risk of SARS-CoV-2 infection, Kaplan said, "once you're infected, your risk of serious complications — requiring hospitalization, ICU stays, ventilation — have all been shown to go up in previous studies.

"This is a different kind of study and much larger," said Kaplan, who is also immediate past-president of The Obesity Society.

Studies also are beginning to demonstrate that bariatric surgery "actually dramatically reduces the risks," Kaplan said. People who underwent the procedure, most many years before the pandemic, tend to fare better when they have COVID-19 compared with people with the same BMI now.

More research is needed to confirm these initial findings, however, Kaplan said. "Although the studies are not yet big enough to show statistical significance, they show dramatic decreases in ICU stays, ventilator use, and death."

The study authors and Kaplan have disclosed no relevant financial relationships. 

MMWR. Published online March 8, 2021. Full text

Damian McNamara is a staff journalist based in Miami. He covers a wide range of medical specialties, including infectious diseases, gastroenterology and critical care. Follow Damian on Twitter:  @MedReporter.

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