In the past year, many scientific teams around the world have reported that obese people who contract the coronavirus are especially likely to become seriously ill.
Now, a large new study, of nearly 150,000 adults in more than 200 hospitals across the United States, paints a more detailed picture of the connection between weight and Covid-19 results.
The study, carried out by a team of researchers at the Center for Disease Control and Prevention, confirmed that obesity significantly increases the risk of hospitalization and death among those who contract the virus. And among those who are obese, the risk increases as the patient’s body mass index, or BMI, a relationship between weight and height, increases. Patients with a BMI of 45 or more, which corresponds to severe obesity, were 33 percent more likely to be hospitalized and 61 percent more likely to die than those with healthy weight, the researchers found.
“The study results highlight the serious clinical implications for public health of elevated BMI and suggest the continued need for intensive treatment for Covid-19 disease, especially among patients affected by severe obesity,” said lead author Lyudmyla Kompaniyets, a health economist at the CDC’s Nutrition, Physical Activity and Obesity Division
But the relationship between weight and results is nuanced. Patients with Covid-19 who were underweight were also more likely to be hospitalized than those with healthy weight, although they were not more likely to be admitted to the intensive care unit or die.
Dr. Kompaniyets and colleagues used a Covid-19 case database to identify 148,494 adults who were diagnosed with the disease in American hospitals from March through December. They calculated the BMI of each patient and looked for correlations between BMI and a variety of serious outcomes, including hospitalization, ICU admission, mechanical ventilation and death.
They found that obesity, which is defined as a BMI of 30 or more, increases the risk of hospitalization and death. Patients with a BMI of 30 to 34.9 were only 7% more likely to be hospitalized and 8% more likely to die than people with a healthy weight, but the risks increased dramatically as the BMI increased.
Providing evidence for this type of “dose-response” relationship makes the study particularly attractive, said Dr. Anne Dixon, director of pulmonary medicine and intensive care at the University of Vermont Medical Center, who was not involved in the research. “What this shows is that the more severe your obesity, the worse the effect. And the fact that it gradually increases with increasing levels of obesity, I think, adds a kind of biological plausibility to the relationship between obesity and the outcome. “
The connection between obesity and poor outcomes was strongest among patients under the age of 65, but it has remained even for older adults. Previous smaller studies have not found strong links between obesity and Covid-19 severity in older adults.
“Potentially because they had more power in this large sample size, they demonstrated that obesity remains an important risk factor for death in older adults as well,” said Dr. Michaela R. Anderson, a specialist in pulmonary and care medicine. at Columbia University Medical Center, which did not participate in the study. “It is a very well done study with a large population.”
Dr. Kompaniyets and her colleagues also documented a linear relationship between BMI and the likelihood of needing mechanical ventilation; the higher the BMI, the greater the probability that the patient will need this intervention, which is invasive and can come with serious complications.
The study also found that patients who were underweight, with a BMI below 18.5, were 20 percent more likely to be hospitalized than those with a healthy weight. The reasons are not entirely clear, but they may be due to the fact that some of these patients are malnourished or fragile or have other diseases.
The BMI range associated with the best results, the researchers found, was close to the dividing line between what is considered healthy and overweight, consistent with some previous research suggesting that a few extra pounds can help protect people when they contract a disease. infectious.
“It is not known exactly why this association exists,” said Dr. Alyson Goodman, a pediatrician and epidemiologist at the CDC and co-author of the study. One possibility is that having a little extra fat can provide the necessary energy reserves throughout a long illness.
The results highlight the importance of carefully managing the care of critically obese patients and ensuring that obese people have access to vaccines and other preventive measures.
“It just provides more evidence for the recommendation to vaccinate those with a high BMI as early as possible,” said Sara Y. Tartof, an infectious disease epidemiologist at the Kaiser Permanente Research and Evaluation Department, who was not involved in the study.