BMI and Risk for Intubation or Death in SARS-CoV-2
- Conflicting data exist on the liability versus protective effects of obesity on respiratory outcomes after lung transplantation and critical illness.
- Obese patients with SARS-CoV-2 infection have been shown to have higher risk of adverse outcomes, but to date, no defined relationship, taking into account the limits of age on BMI and outcome, has been defined.
In patients who are hospitalized with a diagnosis of coronavirus disease 2019 (COVID-19), how does obesity affect risk of death, respiratory failure requiring intubation, or elevation of biomarkers indicating inflammation, myocardial injury, and fibrinolysis?
In this retrospective cohort study, the authors examined an electronic database of 2,466 consecutive patients hospitalized with COVID-19 between March 10–April 24, 2020 at NY Presbyterian/Columbia University Irving Medical Center and an affiliated community hospital. Data including body mass index (BMI), age, sex, and circulating C-reactive protein, erythrocyte sedimentation rate, high-sensitivity troponin, and D-dimer collected on admission were compiled. Cox proportional hazards models, adjusted by factors including age, diabetes, and various comorbid cardiopulmonary conditions, were used to evaluate the time-to-event relationship of BMI and composite outcome of death or respiratory failure requiring intubation. Body size by BMI (kg/m2) was categorized as underweight (≤18.5), normal (18.5-24.9), overweight (25-29.9), or obese (≥30.0), sub-categorized as class 1 (30-34.9), class 2 (35-39.9), or class 3 (≥40).
A total of 2,466 adult patients were included in the analysis. The median (interquartile range) hospital length-of-stay was 7 (3-14) days. Among the patient population: 533/2,466 (22%) were intubated, 627/2,466 (25%) died, and 59/2,466 (2%) remained hospitalized by the end of the study period. Greater risk of death or respiratory failure requiring intubation was observed in obese compared with overweight patients; among the obese, the highest risk was seen among the class 3 subcategory (BMI ≥40 kg/m2, hazard ratio, 1.6; 95% confidence interval, 1.1-2.1). However, the association between obesity and risk of adverse outcome was observed only in patients ≤65 years, but not among patients >65 years of age (p for interaction by age = 0.042). Patients in the underweight category showed higher rates of the primary outcome versus normal and overweight individuals, indicating a j-shaped relationship between body size and risk. No significant association between obesity and biomarker elevation at the time of hospital admission was observed.
Obesity, especially in the extremes (BMI ≥40 kg/m2), confers greater risk of death or clinical deterioration requiring intubation, regardless of age or comorbidities, but the relationship is not sustained in patients >65 years of age.
Although previously cited sources suggest that obesity is more common among patients requiring hospitalization after a diagnosis of COVID-19, at the same time, conflicting data show a protective effect of obesity on critically ill patients who are at risk of adverse respiratory outcomes. Numerous theories on how obesity might impact outcome are discussed. Bulk fat contains a high concentration of proinflammatory immune cells capable of producing cytokines including interleukin-6, which may play a role in the pathogenesis of lung injury in advanced COVID-19 infection. Second, conditions associated with obesity are themselves known to cause or accelerate cardiovascular disease. The authors cite need for better understanding of risk factors associated with death and respiratory failure in COVID-19 infection, and based on their findings, speculate on whether obese subjects, especially those <65 years of age, would be better protected by more stringent regulations for social distancing during the pandemic, due to the apparent greater attendant risk of adverse COVID-19-related outcomes.
Keywords: Body Mass Index, Coronavirus Infections, COVID-19, C-Reactive Protein, Critical Illness, Fibrinolysis, Inflammation, Interleukin-6, Intubation, Metabolic Syndrome X, Obesity, Primary Prevention, Respiration, Artificial, Risk Factors, severe acute respiratory syndrome coronavirus 2, Thinness, Troponin
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