The probability that a person with obesity will develop severe COVID-19 is high regardless of age, sex, ethnicity and the presence of co-morbidities such as diabetes, high blood pressure, and heart or lung disease, according to a Brazilian study.
The systematic review and meta-analysis of relevant data in the scientific literature focus on nine clinical studies, which in aggregate reported the evolution of 6,577 COVID-19 patients in five countries. The study, ‘Coronavirus (SARS-CoV-2) and the risk of obesity for critically illness and ICU admitted: Meta-analysis of the epidemiological evidence’, published in Obesity Research & Clinical Practice, concluded that obesity is itself a factor that favours rapid progression to critical illness requiring intensive care and significantly increases the risk of death. The associated research project was supported by São Paulo Research Foundation (FAPESP).
"Several factors contribute to the progression to critical illness in the obese organism. One is the limited capacity to produce interferons [a class of proteins secreted by defence cells and essential to inhibit viral replication] and antibodies,” said Silvia Sales-Peres , a professor at the University of São Paulo (USP) in Bauru and principal investigator for the project. “In addition, adipose tissue functions as a reservoir for the virus, maintaining it in the organism for longer.”
This potentially higher viral load, she explained, is not the only problem faced by patients with a high body mass index (BMI). Recent research shows that the chronic low-grade inflammation typical of obesity - caused by excessive expansion of adipose cells - makes the inflammatory cytokine storm triggered by SARS-CoV-2 even more damaging to the lungs.
"Patients with obesity usually present with impaired respiratory function, as abdominal adipose tissue compresses the diaphragm and prevents it from moving normally," added Sales-Peres. "In sum, various concurrent factors make these patients more predisposed to dependency on mechanical ventilation and other kinds of intensive care if they contract COVID-19. In the studies we analysed, 9.4% of the obese patients treated in intensive care units died."
Almost 60% of Brazilians are overweight and some 20% have obesity, according to the Health Ministry's telephone surveillance survey on risk factors for chronic diseases (Vigitel).
"A higher degree of susceptibility to the novel coronavirus when a person reaches a certain number on the BMI scale is no accident. Impaired antibody production and chronic inflammation favour progression of COVID-19 in overweight subjects," she explained. "Our analysis also showed that the risk associated with obesity is even greater for smokers or subjects with co-morbidities such as diabetes, hypertension and lung disease."
She went on to argue that studies like this are important both to alert patients to the need to protect themselves against the virus and to help health services prepare for the potential demand for intensive care.
"We embarked on the study in April when it wasn't so clear that obesity would be considered a major risk factor for COVID-19," she said.
For the systematic review, the authors first searched Medline, Embase, Web of Science, BVS/Lilacs, SciELO, Scopus, and Google Scholar to select studies published on or before April 27 using key terms such as obesity and COVID-19. In total, 6,577 patients were selected for evaluation. The COVID-19 patients were 59.80% male and had comorbidities such as hypertension (51.51%), diabetes (30.3%), cardiovascular disease (16.66%), lung disease (15.99%), renal disease (7.49%), cancer (5.07%) and immunosuppression (1.8%).
For patients with severe complications, the overall pooled event rates were 56.2% (random; 95% CI: 35.3–75.1; p=0.015; I2 = 71.461) for obesity, 23.6% (random; 95% CI: 17.9–30.5; p=0.000; I2 = 87.705) for type 2 diabetes, 45.9% (random; 95% CI: 38.0–53.9; p=0.000; I2 = 90.152) for hypertension, 20.0% (random; 95% CI: 7.9–42.0; p=0.000; I2 = 94.577) for smoking, 21.6% (random; 95% CI: 14.1–31.4%; p=0.000, I2 = 92.983) for lung diseases, and 20.6% (random; 95% CI: 15.2–27.5; p=0.000, I2 = 85.735) for cardiovascular diseases.
“This meta-analysis revealed that patients with severe obesity are at high risk of severe COVID-19 infection, IMV, ICU admission, and mortality, independent of age, race, sex, and comorbidities such as diabetes, hypertension, dyslipidaemia or pulmonary disease,” the authors concluded. “This systematic review showed that obese COVID-19 patients with associated comorbidities required special care due to increased risk of in-hospital death.”
"The 2018 Vigitel survey pointed to 30% growth in the overall prevalence of overweight in Brazil compared with 2006. Considering only the 18-24 group, the increase was 55.7%. This makes discussing the risk of severe COVID-19 associated with obesity extremely important," explained Sales-Peres.
Public health policy should promote an integrated and intersectoral approach to obesity, she argued, and should have regulatory and enforcement authority.
"There should be a transformational mobilisation to encourage outdoor physical exercise and healthy dietary habits from early childhood," she said. "This should be a coordinated initiative across all three tiers of government so as to enable integrated planning, funding, and strategy to promote wellness and prevent obesity."
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