Over the past year, many scientific teams around the world have reported that obese people who contract the coronavirus are particularly likely to get dangerously ill.
Now, a great new studyA more detailed picture of the relationship between weight and Covid-19 results is emerging from nearly 150,000 adults in more than 200 hospitals in the United States.
The study, conducted by a team of researchers as Centers for Disease Control and Prevention, confirmed that obesity significantly increases the risk of hospitalization and death in those who contract the virus. And in obese people, the risk increases when a patient’s body mass index, or B.M.I., a ratio of weight to height, increases. Patients with a B.M.I. of 45 or more, which equates to severe obesity, 33 percent were more likely to be hospitalized and 61 percent more likely than those who were of healthy weight, the researchers found.
“The results of the study underscore the serious clinical public health implications of elevated BMI and suggest the continued need for intensive treatment for Covid-19 disease, particularly in patients with severe obesity,” said lead author Lyudmyla Kompaniyets, a Health economist with the Department of Nutrition, Physical Activity, and Obesity at the CDC
However, the relationship between weight and results is nuanced. Underweight Covid-19 patients were also hospitalized more often than healthy-weight patients, although they were not admitted to the intensive care unit or died more often.
Dr. Kompaniyets and her colleagues used a database of Covid-19 cases to identify 148,494 adults who were diagnosed with the disease in American hospitals from March to December. They calculated the B.M.I. from each patient and looked for correlations between B.M.I. and a variety of serious consequences including hospitalization, I.C.U. Admission, mechanical ventilation, and death.
They found that obesity, classified as B.M.I. of 30 or higher increased the risk of hospitalizations and death. Patients with a B.M.I. from 30 to 34.9 were only 7 percent more likely to be in hospital and 8 percent more likely to die than people of healthy weight, but the risks increased sharply when B.M.I. Rose.
The provision of evidence for this type of “dose-response relationship” makes the study particularly compelling, said Dr. Anne Dixon, director of pulmonary and critical care at the University of Vermont Medical Center, who was not involved in the research. “What it shows is the more severe your obesity, the worse the effect. And the fact that it gradually increases as obesity increases, I believe adds some kind of biological plausibility to the relationship between obesity and the outcome. “
The association between obesity and poor outcomes was strongest in those under 65, but it was also true in older adults. Previous, smaller studies did not find strong associations between obesity and Covid-19 severity in older adults.
“Potentially because they had more strength from this large sample, they showed that obesity remains a major risk factor for death even in older adults,” said Dr. Michaela R. Anderson, an expert in pulmonary and critical care medicine at Columbia University Medical Center, who was not involved in the study. “It’s a beautifully done study with a huge population.”
Dr. Kompaniyets and her colleagues also documented a linear relationship between B.M.I. and the likelihood that mechanical ventilation will be required; The higher the B.M.I., the more likely it was that a patient would need such an intervention, which is invasive and can have serious complications.
The study also found that patients who were underweight with a B.M.I. Those below 18.5 were 20 percent more likely to be hospitalized than those of a healthy weight. The reasons are not entirely clear, but may be due to the fact that some of these patients were malnourished, frail, or had other illnesses.
The B.M.I. The area associated with the best results was near the dividing line between healthy and obese, according to researchers, which is in line with some previous research suggesting that a few extra pounds could help protect people from an infectious disease.
“It is not currently known exactly why this association exists,” said Dr. Alyson Goodman, pediatrician and medical epidemiologist at the C.D.C. and a co-author of the study. One possibility is that a little extra fat can provide much-needed energy reserves over the course of a long illness.
The results show the importance of carefully managing the care of patients with severe obesity and ensuring that people with obesity have access to vaccines and other preventive measures.
“This is just further evidence of the recommendation to vaccinate people with a high B.M.I. as early as possible, ”said Sara Y. Tartof, infectious disease epidemiologist at Kaiser Permanente’s Department of Research & Evaluation, who was not involved in the study.