COVID-19 and obesity poor outcomes not driven by inflammation

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Obesity is associated with poor novel coronavirus (COVID-19) outcomes, however this is not due to increased inflammation, but instead may be driven by respiratory issues or other factors, according to new research by the Boston University School of Medicine published in the journal PLOS One.

For the study, researchers compared outcomes and inflammatory markers in patients with and without obesity who were hospitalized with COVID-19.

They found that body mass index (BMI) greater or equal to 35 was associated with a two-fold increased risk of intensive care unit (ICU) transfer and a four-fold risk of all-cause mortality. Additionally, BMI in the 30 to 34.9 range, or class 1 obesity, was also associated with increased risk of ICU transfer, but not significantly associated with increased mortality.

The researchers also found that patients with obesity had mostly lower inflammatory markers on the first and second hospital days compared to those without obesity.

Multiple studies suggest those who are overweight or have obesity are more likely to experience invasive mechanical ventilation, ICU admission or death. Population-level studies also suggest a higher COVID-19 mortality rate in countries with greater prevalence of obesity. What was not known before was whether patients with obesity had more inflammation, the so-called cytokine storm of COVID.

According to the researchers, additional factors may explain the unexpected finding of lower inflammatory markers in patients with obesity. 

The researchers said they believe further studies are needed to determine whether this decreased inflammatory response persists during hospitalization, whether pro-inflammatory complications are seen less commonly among patients with obesity and whether anti-inflammatory therapy should be utilized differently in patients with obesity.

"While patients with obesity had worse clinical outcomes than those without obesity in our study, this effect does not appear to be mediated by a higher degree of inflammation," said Natasha Hochberg, MD, associate professor of medicine at Boston University School of Medicine and an infectious disease physician, in a statement. "Patients with obesity are at higher risk of fatty liver disease and greater viral invasion with organ dysfunction may contribute to the increased mortality seen in these patients. Alternately, patients with obesity may have reduced respiratory reserve."

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