Body Mass Index and Risk for Intubation or Death in SARS-CoV-2 Infection : A Retrospective Cohort Study

Abstract

Background: Obesity is a risk factor for pneumonia and acute respiratory distress syndrome.

Objective: To determine whether obesity is associated with intubation or death, inflammation, cardiac injury, or fibrinolysis in coronavirus disease 2019 (COVID-19).

Design: Retrospective cohort study.

Setting: A quaternary academic medical center and community hospital in New York City.

Participants: 2466 adults hospitalized with laboratory-confirmed severe acute respiratory syndrome coronavirus 2 infection over a 45-day period with at least 47 days of in-hospital observation.

Measurements: Body mass index (BMI), admission biomarkers of inflammation (C-reactive protein [CRP] level and erythrocyte sedimentation rate [ESR]), cardiac injury (troponin level), and fibrinolysis (D-dimer level). The primary end point was a composite of intubation or death in time-to-event analysis.

Results: Over a median hospital length of stay of 7 days (interquartile range, 3 to 14 days), 533 patients (22%) were intubated, 627 (25%) died, and 59 (2%) remained hospitalized. Compared with overweight patients, patients with obesity had higher risk for intubation or death, with the highest risk among those with class 3 obesity (hazard ratio, 1.6 [95% CI, 1.1 to 2.1]). This association was primarily observed among patients younger than 65 years and not in older patients (P for interaction by age = 0.042). Body mass index was not associated with admission levels of biomarkers of inflammation, cardiac injury, or fibrinolysis.

Limitations: Body mass index was missing for 28% of patients. The primary analyses were conducted with multiple imputation for missing BMI. Upper bounding factor analysis suggested that the results are robust to possible selection bias.

Conclusion: Obesity is associated with increased risk for intubation or death from COVID-19 in adults younger than 65 years, but not in adults aged 65 years or older.

Primary funding source: National Institutes of Health.

Visual Abstract.. BMI and Risk for Intubation or Death in SARS-CoV-2 Infection

Obesity has been associated with COVID-19 and with pneumonia and acute respiratory distress syndrome but is also associated with comorbidities that place patients at higher risk. This study examines whether obesity is associated with intubation or death—as well as biomarkers of inflammation, cardiac injury, or fibrinolysis—in the context of COVID-19 disease independent of obesity-related comorbidities.

Figure 1.. Study flow diagram.

ED = emergency department; SARS-CoV-2 = severe acute respiratory syndrome coronavirus 2.

Figure 2.. Association between body mass index and odds of a composite end point of intubation or death.

Additive Cox models with penalized splines adjusted for age, sex, race/ethnicity, and comorbid conditions were created. The vertical lines along the x axis represent individual study patients.

Figure 3.. Forest plots of multivariable-adjusted associations between body mass index and composite end point of death or intubation by prespecified stratification variables.

Body mass index was categorized as underweight (<18.5 kg/m²), normal (18.5 to 24.9 kg/m²), overweight (25 to 29.9 kg/m²), class 1 obesity (30 to 34.9 kg/m²) class 2 obesity (35 to 39.9 kg/m²), or class 3 obesity (≥40 kg/m²). Overweight is the reference category for the HRs. Subgroup sizes are based on patients with known body mass index. Effect estimates were generated from multiple imputation models. HR = hazard ratio.

Appendix Figure.. Scatter plots evaluating the association between body mass index and biomarkers of inflammation, cardiac injury, and fibrinolysis.

FEU = fibrinogen equivalent units. A. C-reactive protein level (1916 patients; r = –0.02; P = 0.38). To convert values to nmol/L, multiply by 9.524. B. Erythrocyte sedimentation rate (1815 patients; r = 0.03; P = 0.25). C. Troponin level (1915 patients; r = –0.15; P < 0.001). D. D-dimer level (1678 patients; r = –0.12; P < 0.001). To convert values to nmol/L, multiply by 5.476.