Obesity has been shown to be a strong independent predictor of not only Covid-19-related hospitalization but also critical illness requiring invasive mechanical ventilation (IMV) or ICU support (1-3).
A large New York City study involving over 4,000 Covid-19 patients found obesity ( BMI≥30 kg/m2) to be an independent risk factor for hospitalization; BMI 30-40 kg/m2 was associated with ~4-fold and >40 kg/m2 with ~6-fold increased risk. Obesity was also strongly associated with increased risk of critical illness, stronger than other common preexisting conditions such as heart disease, hypertension or diabetes (1, preprint).
Another New York City study found that among Covid-19 patients younger than 60 years of age, obese patients were twice as likely to be hospitalized or have critical illness (2). Similarly, a French study found severe obesity (BMI >35 kg/m2) to be strongly associated with IMV compared to those with BMI <25 kg/m2 (O.R. 7.4, 1.7-33) (3).
Many factors likely play a role in making obese patients particularly susceptive to severe Covid-19. Obesity is a well-recognized inflammatory state and is associated with abnormal secretion of cytokines and adipokines which may have an effect on lung parenchyma and bronchi (1,3,4). Somewhat paradoxically, obese patients may also have an impaired adaptive immune response to certain infections, including influenza (4). Abdominal obesity is also associated with impaired ventilation of the base of the lungs resulting in reduced oxygenation (1).
Bonus Pearl: Did you know among pre-existing conditions commonly found in the population (eg, hypertension, diabetes, COPD), obesity has been found to be the only condition independently associated with pulmonary embolism in Covid-19 (O.R. 2.7, 1.3-5.5) (5).
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References
1. Petrilli CM, Jones SA, Yang J, et al. Factors associated with hospitalization and critical illness among 4, 103 patients with Covid-19 disease in New York City. MedRxiv preprint doi: https://doi.org/10.1101/2020.04.0820057794
2. Lighter J, Phillips M, Hochman S, et al. Obesity in patients younger than 60 years is a risk factor for COVID-19 hospital admission. Clin Infect Dis 2020. https://pubmed.ncbi.nlm.nih.gov/32271368/
3. Simonnet A, Chetboun M, Poissy J, et al. High prevalence of obesity in severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) requiring invasive mechanical ventilation. https://pubmed.ncbi.nlm.nih.gov/32271993/
4. Sattar N, BcInnes IB, McMurray JJV. Obesity a risk factor for severe COVID-19 infection:multiple potential mechanisms. Circulation 2020. https://www.ahajournals.org/doi/pdf/10.1161/CIRCULATIONAHA.120.047659
5. Poyiadji N, Cormier P, Patel PY, et al. Acute pulmonary embolism and COVID-19. Radiology 2020; https://pubmed.ncbi.nlm.nih.gov/32407256/
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