Obesity Worsens Outcomes in COVID-19, Especially for Younger Adults

Obesity, especially when severe, increases the use of mechanical ventilation as well as death in COVID-19 and carries particular risk for younger adults, new data from the American Heart Association (AHA) COVID-19 CVD registry confirm.

“Clear public health messaging is needed for younger obese individuals who may underestimate their risk of severe COVID-19,” said Nicholas S. Hendren, MD (University of Texas Southwestern Medical Center, Dallas), who presented the study at a late-breaking clinical trial session during the AHA’s virtual 2020 Scientific Sessions.

Relatively early in the COVID-19 pandemic, clinicians and researchers warned that, independent of other CV risk factors, obesity appeared to portend worse outcomes among infected patients. But as Hendren pointed out, younger adults are typically lower risk for severe COVID-19—just how much obesity might mitigate the protective effects of youth was unclear.

Hendren and colleagues put the question to the AHA’s registry, launched in early April. As co-author James de Lemos, MD (University of Texas Southwestern Medical Center, Dallas), showed earlier in the same session, 109 centers are participating in the registry, which at the time of the AHA presentations had collected more than 22,500 records for patients hospitalized with COVID-19. Hendren’s body mass index (BMI) analysis included 7,606 hospitalized adults with a COVID-19 diagnosis and available BMI data as of July 22, 2020, with patients categorized as underweight, normal weight, overweight, or obesity class 1, 2, or 3 as defined by the World Health Organization and the Centers for Disease Control and Prevention.

Baseline characteristics of hospitalized patients clearly show that the median age of patients with all three levels of obesity is younger than that of those who were overweight, normal weight, or underweight. Black Americans were also disproportionately represented in the group with class 3 obesity, making up 40% of that cohort followed by white (31%) and Hispanic (23%). A full picture of the disproportionate burden of COVID-19 illness experienced by Black and Hispanic patients included in the AHA’s registry was presented separately, as reported by TCTMD.

Using normal-weight patients as the comparator, rates of death or mechanical ventilation increased in a stepwise fashion with increasing weight levels, a finding driven by rates of mechanical ventilation. After adjustment for other risk factors, any BMI ≥ 30 kg/m² was associated with an increased risk of ending up on a ventilator. By contrast, risk of dying was only significantly increased in patients with a BMI ≥ 40 kg/m².

In further analyses that stratified primary and secondary outcomes by age, Hendren et al found that in-hospital death or mechanical ventilation was significantly associated with increasing BMI  in the under-50 age group and the 50-70 age group, but not in patients older than age 70. In-hospital death was only increased with higher BMIs in patients under age 50, while risk of needing mechanical ventilation increased with successive BMI levels in all three age groups.

“Clear public health messaging is needed for younger obese individuals who may underestimate their risk of severe COVID-19,” Hendren concluded.

Ron Blankstein, MD (Brigham and Women's Hospital, Boston, MA), a member of the Prevention Section and Leadership Council for the American College of Cardiology, pointed out to TCTMD that while other studies have looked at obesity as a risk factor in COVID-19, this is by far the largest series to date. What’s striking, he said, is that of all the patients under age 50 who ended up in hospital in this series, the majority were obese.

“I think it should reinforce the notion, especially for young individuals—and many of them may currently think they are not at risk for significant COVID disease—that if they are obese, they actually are at higher risk for hospital admission,” said Blankstein. “And if they get admitted to hospital, they then are also at risk for needing mechanical ventilation or dying.”

Young, Obese, at Risk

Speaking during a press conference, de Lemos speculated that obesity increases the risk of severe COVID-19 in at least three different ways. “One is the concomitant risk factors that go along with obesity: a larger burden of diabetes, hypertension, and other cardiovascular risk factors. There’s also, with regard to the respiratory issues, just the mechanical disadvantage of severe obesity that seems to be present in other respiratory illness, that almost certainly contributes to the higher rates of mechanical ventilation and pulmonary morbidity,” he explained to TCTMD. “The final thing relates to the effects of the virus on the activation of the renin angiotensin system, which is already dramatically upregulated in individuals who are obese. So it’s a synergy of the virus’s pathologic effects [and] the vulnerable person, on the basis of their obesity with regard to ACE2 levels.”

The findings have both immediate and far-reaching implications, said Blankstein. “One of the really important points now, as we're entering the worst phase of the pandemic, is that if you're obese you're at higher risk and you need to be that much more concerned in protecting yourself and your family members, wearing a mask, not going out to crowed places, avoiding indoor interactions with folks—all the measures that we keep hearing about that unfortunately our county as a whole is not doing a good job with—and to know that if you're obese you're at high risk. That's an important message that everyone needs to know.”

Long-term, he continued, it’s already well established that obesity increases the risk of diabetes, hypertension, and coronary heart disease as well as a host of noncardiac diseases. “When this pandemic is over and we decide as a country to tackle obesity, this is yet one more thing to add to the conglomerate of adverse health effects of obesity,” Blankstein said. “Who knows when the next pandemic will be, but when we talk about all the benefits of avoiding obesity in our population this should be one of the factors we should think about.”