Body Mass Index and Mortality in Coronavirus Disease 2019 and Other Diseases: A Cohort Study in 35,506 ICU Patients

Abstract

Objectives: Obesity is a risk factor for severe coronavirus disease 2019 and might play a role in its pathophysiology. It is unknown whether body mass index is related to clinical outcome following ICU admission, as observed in various other categories of critically ill patients. We investigated the relationship between body mass index and inhospital mortality in critically ill coronavirus disease 2019 patients and in cohorts of ICU patients with non-severe acute respiratory syndrome coronavirus 2 viral pneumonia, bacterial pneumonia, and multiple trauma.

Design: Multicenter observational cohort study.

Setting: Eighty-two Dutch ICUs participating in the Dutch National Intensive Care Evaluation quality registry.

Patients: Thirty-five-thousand five-hundred six critically ill patients.

Interventions: None.

Measurements and main results: Patient characteristics and clinical outcomes were compared between four cohorts (coronavirus disease 2019, nonsevere acute respiratory syndrome coronavirus 2 viral pneumonia, bacterial pneumonia, and multiple trauma patients) and between body mass index categories within cohorts. Adjusted analyses of the relationship between body mass index and inhospital mortality within each cohort were performed using multivariable logistic regression. Coronavirus disease 2019 patients were more likely male, had a higher body mass index, lower Pao2/Fio2 ratio, and were more likely mechanically ventilated during the first 24 hours in the ICU compared with the other cohorts. Coronavirus disease 2019 patients had longer ICU and hospital length of stay, and higher inhospital mortality. Odds ratios for inhospital mortality for patients with body mass index greater than or equal to 35 kg/m2 compared with normal weight in the coronavirus disease 2019, nonsevere acute respiratory syndrome coronavirus 2 viral pneumonia, bacterial pneumonia, and trauma cohorts were 1.15 (0.79-1.67), 0.64 (0.43-0.95), 0.73 (0.61-0.87), and 0.81 (0.57-1.15), respectively.

Conclusions: The obesity paradox, which is the inverse association between body mass index and mortality in critically ill patients, is not present in ICU patients with coronavirus disease 2019-related respiratory failure, in contrast to nonsevere acute respiratory syndrome coronavirus 2 viral and bacterial respiratory infections.

Figure 1.

Distribution of body mass index for the coronavirus disease 2019 (COVID-19), nonsevere acute respiratory syndrome coronavirus 2 (SARS-CoV-2) viral pneumonia, bacterial pneumonia, and multiple trauma cohorts. The proportion of patients with overweight and obesity was notably higher in COVID-19 patients compared with the other cohorts.

Figure 2.

Relative inhospital mortality risks according to body mass index (BMI) in the four cohorts. BMI of 25.0 kg/m² was used as reference. Relative risks were adjusted for sex, age, chronic diagnosis, Acute Physiology and Chronic Health Evaluation III Acute Physiology Score and need for mechanical ventilation, use of vasoactive medication, and lowest Pao₂/Fio₂ ratio in the first 24 hr following ICU admission. The mortality risk decreases with higher BMI in the nonsevere acute respiratory syndrome coronavirus 2 (SARS-CoV-2) viral pneumonia, bacterial pneumonia, and trauma cohorts, but not in coronavirus disease 2019 (COVID-19) patients.