In a recent blog post, I discussed emerging data that suggested obesity as a risk factor for more severe COVID-19 infection. At that time (less than a month ago), there was no data to tell us if obesity is a risk factor only in people with obesity-related medical conditions, or whether obesity could be a risk factor in people without any known obesity-related medical conditions.


New data points towards obesity as a stand-alone risk factor for more severe coronavirus infection.


A study of 4103 patients diagnosed with COVID-19 in New York City looked at risk factors for hospitalization, and risk factors for critical illness (defined as needing ICU care, mechanical ventilation, hospice care, and/or death). In a multivariable analysis, compared with people without obesity (BMI <30), they found that people with severe obesity (BMI >40) had a 6.2 times higher risk for hospitalization, and people with mild to moderate obesity (BMI 30-40) had a 4.3 higher risk of hospitalization. They found that the most important predictors for hospitalization were age over 65, followed by obesity.  In other words, the chronic health condition with the  strongest association with critical illness was obesity.


A Chinese study recently reported on 383 patients admitted to hospital for COVID infection.  They defined obesity as a BMI of 28 or greater (lower BMI criteria for obesity are used in China).  They found that people with obesity had a 2.4 times higher risk of developing severe pneumonia, compared to people with healthy range BMI (18.5-24), independent of other chronic medical conditions (including hypertension, diabetes, cardiovascular disease, cancer, and liver disease), and adjusted for age, gender, and other epidemiological characteristics.


Finally, a French study of patients admitted to ICU for coronavirus found that, compared to people with BMI <25, people with BMI 30-35 had a 3.5 times higher risk of needing invasive mechanical ventilation, and people BMI >35 had a 7.4 times higher risk of needing mechanical ventilation, independent of other risk factors including age, diabetes, and hypertension (multivariate analysis).


BOTTOM LINE: As suspected, we are now seeing data proving that obesity is a stand alone risk factor for more severe COVID-19 infection.  In my recent blog post, I talked about a number of reasons why obesity is a risk factor for more severe infection.  What we have learned in the last few weeks is that a severe inflammatory response or ‘cytokine storm’ characterizes many severe infections.  We know that people with obesity have a chronic inflammatory state, so this may be at least partly responsible for the higher risk of more severe infection.  This profound inflammatory reaction during a COVID infection can lead to disseminated intravascular coagulation.  Severe illness has also been seen to be complicated in some cases by pulmonary embolism (a blood clot that usually starts in the legs and then travels to the lungs), and we know that obesity is a risk factor for pulmonary embolism as well.


It is increasingly clear that obesity is a risk factor for more severe COVID-19 infection, and that avoidance of contracting this infection is paramount.  Check out my previous blog posts for tips on avoiding infection, including the critical importance of continued physical distancing and hand hygiene.


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