Obesity Link to Severe COVID-19, Especially in the Under 60s

Liam Davenport and Lisa Nainggolan

April 16, 2020

Editor's note: Find the latest COVID-19 news and guidance in Medscape's  Coronavirus Resource Center.

It is becoming increasingly clear that obesity is one of the biggest risk factors for severe COVID-19 disease, particularly among younger patients.

Newly published data from New York show that among those under 60, obesity was twice as likely to result in hospitalization for COVID-19 and also significantly increased the likelihood that a person would end up in intensive care.

"Obesity [in people < 60 years] appears to be a previously unrecognized risk factor for hospital admission and need for critical care. This has important and practical implications when nearly 40% of adults in the US are obese with a body mass index [BMI] of ≥ 30," write Jennifer Lighter, MD, NYU School of Medicine/NYU Langone Health, and colleagues in their research letter published online April 9 in Clinical Infectious Diseases.

Similar findings in a preprint publication, yet to be peer reviewed, from another New York hospital show that, with the exception of older age, obesity (BMI > 40 kg/m2) had the strongest association with hospitalization for COVID-19, increasing the risk more than sixfold.  

Meanwhile, a new French study shows a high frequency of obesity among patients admitted to one intensive care unit for COVID-19; furthermore, disease severity increased with increasing BMI.

One of the authors told Medscape Medical News that many of the presenting patients were younger, with their only risk factor being obesity.

"Patients with obesity should avoid any COVID-19 contamination by enforcing all prevention measures during the current pandemic," say the authors, led by Arthur Simonnet, MD, Centre Hospitalier Universitaire de Lille, France.

They also stress COVID-19 patients "with severe obesity should be monitored more closely."

Those With Obesity Are Young and Become Very Sick, Very Quickly

Coauthor of the French article, published online April 9 in Obesity, François Pattou, MD, PhD, told Medscape Medical News that when patients with COVID-19 began to arrive at their intensive care unit in Lille there were young patients who did not have any other comorbidities.

"They were just obese," he observed, adding that they seemed "to have a very specific disease, something different" from that seen before, with patients becoming very sick, very quickly.

In their study, they examined 124 consecutive patients admitted to intensive care with COVID-19 between February 25 and April 5, 2020, and compared them with a historical control group of 306 patients admitted to the ICU at the same hospital for non-COVID-19-related severe acute respiratory disease in 2019.

By April 6, 60 patients with COVID-19 had been discharged from intensive care, 18 had died, and 46 remained in the unit. The majority (73%) were male, and their median age was 60 years.

Obesity and severe obesity were significantly more prevalent among the patients with COVID-19, at 47.6% and 28.2%, versus 25.2% and 10.8% among historical controls (P < .001 for trend).

A key finding was that those with a BMI > 35 kg/m2 had a more than sevenfold increased risk of requiring mechanical ventilation (odds ratio [OR], 7.36; P = .021), compared to those with a BMI < 25 kg/m2, even after adjusting for age, diabetes, and hypertension.

Obesity in Under 60s at Least Doubles Risk of Admission in US

The studies out of New York, one of which was stratified by age, paint a similar picture.

Lighter and colleagues found that of the 3615 individuals who tested positive for COVID-19 in their series, 775 (21%) had a BMI 30-34 kg/m2 and 595 (16%) had a BMI ≥ 35 kg/m2.

Obesity wasn't a predictor of admission to hospital or the ICU in those over the age of 60 years, but in those younger than 60 years, it was.

Those under age 60 with a BMI 30-34 kg/m2 were twice as likely to be admitted to hospital (hazard ratio [HR], 2.0; P < .0001) and critical care (HR, 1.8; P = .006) compared to those under age 60 with a BMI < 30 kg/m2.

Likewise, those under age 60 with a BMI ≥ 35 kg/m2 were 2.2 (P < .0001) and 3.6 (P < .0001) times more likely to be admitted to acute and critical care.

"Unfortunately, obesity in people < 60 years is a newly identified epidemiologic risk factor which may contribute to increased morbidity rates [with COVID-19] experienced in the US," they conclude.

And in the other US study, Christopher M. Petrilli, MD, NYU Grossman School of Medicine, and colleagues looked at 4103 patients with COVID-19 treated between March 1 and April 2, 2020, and followed to April 7.

Just under half of patients (48.7%) were hospitalized, of whom 22.3% required mechanical ventilation and 14.6% died or were discharged to hospice. The research was posted April 11 on medRxiv.

It showed that, apart from age, the strongest predictors of hospitalization were BMI > 40 kg/m2 (OR, 6.2) and heart failure (OR, 4.3).

"It is notable that the chronic condition with the strongest association with critical illness was obesity, with a substantially higher odds ratio than any cardiovascular or pulmonary disease," they note.

Is Inflammation the Culprit?

Pattou believes that the culprit behind the increased risk of disease severity seen with obesity in COVID-19 is inflammation, mediated by fibrin deposits in the circulation, which his colleagues have seen on autopsy, and which "block oxygen passage through the blood."

This may help explain why mechanical ventilation can be less successful in these patients.

"The answer is to get rid of this inflammation," Pattou observed.

Petrilli and colleagues also observe that obesity "is well-recognized to be a proinflammatory condition."

And their findings show "the importance of inflammatory markers in distinguishing future critical from noncritical illness," they say, noting that, among these markers, early elevations in C-reactive protein and D-dimer "had the strongest association with mechanical ventilation or mortality."

Livio Luzi, MD, of IRCCS MultiMedica, Milan, Italy, has previously written on the relationship between influenza and obesity, and discussed with Medscape Medical News the potential lessons for the COVID-19 pandemic.

"Obesity is characterized by an impairment of immune response and by a low-grade chronic inflammation. Furthermore, obese subjects have an altered dynamic of pulmonary ventilation, with reduced diaphragmatic excursion," Luzi said.

These factors, alongside others, "may help to explain" the current results, and stress the importance of close monitoring of those with obesity and COVID-19, he concluded.

No relevant financial relationships were declared.

Clin Infect Dis. Published online April 9, 2020. Letter

medRxiv. Published online April 11, 2020. Full text

Obesity. Published online April 9, 2020. Full text

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