Being under 50 years of age does not protect against the dangers of COVID-19 if you are overweight, according to a study from UT Southwestern (UTSW). While all adults who are overweight or have obesity are at greater risk for serious complications from the disease, the link is strongest for those age 50 and under. More than 42 percent of American adults have obesity, according to the Centers for Disease Control and Prevention, and approximately another 30 percent are overweight.
"If you're young . (in the study, young is defined as age 50 or younger) and have obesity you're still at high risk despite your age," said Dr Justin Grodin, senior author of the study, ‘Association of Body Mass Index and Age With Morbidity and Mortality in Patients Hospitalized With COVID-19: Results From the American Heart Association COVID-19 Cardiovascular Disease Registry’, published in Circulation. The study's findings should alert people - who may feel safe because of their age - that they are at greater risk from COVID-19, added Grodin, assistant professor of internal medicine at UT Southwestern. Those with severe obesity, approximately 7 percent of the US adult population, should be considered high risk and may warrant prioritisation for a COVID-19 vaccine when it becomes available, he said.
While the numbers do not explain why obesity worsens outcomes for COVID-19 patients, the study suggests several possibilities. First, obesity is associated with diseases that have been linked to worse outcomes for COVID-19, such as hypertension and diabetes, according to the study. Secondly, the SARS-CoV-2 virus uses an enzyme called ACE2 to enter and infect human cells, and that enzyme is abundant in fat tissue. In addition, simply having more weight on the chest may make it harder for COVID-19 patients to breathe. Also, negative effects tied to obesity may be especially apparent in younger patients because older COVID-19 patients have so many other risk factors, the study noted.
The study analyzed data from more than 7,600 patients at 88 US hospitals who were enrolled in the American Heart Association's (AHA) COVID-19 Cardiovascular Disease Registry. Dr James de Lemos, a UTSW professor of internal medicine, helped create the registry along with volunteers and AHA staff. The study team adjusted its findings of risk to take into account patients' age, sex, race and prior health problems.
Looking at patients age 50 and under hospitalised for COVID-19, the researchers found that the vast majority (85 percent) were either overweight or had obesity. That compares with 54 percent of patients over age 70, making weight more of a risk marker for the younger group. Among patients 50 and under, those with severe obesity had a 36 percent greater risk of dying, compared with normal weight individuals, the study found. Overall, adult patients with severe obesity had a 26 percent higher risk of dying.
Looking at all adult patients, the risk of being sick enough to require a ventilator rose in lock-step as weight increased from overweight to Class III obesity, according to the study. The risk of death also rose for those who had Class III obesity.
"In general, individuals with obesity are more likely to be hospitalised with COVID-19 than normal weight individuals," explained Dr Nicholas Hendren, a UTSW chief cardiology fellow and first author of the study,. "In the hospital, individuals with obesity are at higher risk for death or the need for mechanical ventilation to help them breathe, even if they are young."
In addition to greater risk for death and the need for ventilation, higher BMI also was linked to the need for kidney dialysis and the development of blood clots in deep veins and the lungs, according to the study.
Other studies are underway to examine how various patient characteristics affect COVID-19 risk, using the AHA's COVID Registry, Grodin added.