The obesity paradox in critically ill patients: a causal learning approach to a casual finding

Abstract

Background: While obesity confers an increased risk of death in the general population, numerous studies have reported an association between obesity and improved survival among critically ill patients. This contrary finding has been referred to as the obesity paradox. In this retrospective study, two causal inference approaches were used to address whether the survival of non-obese critically ill patients would have been improved if they had been obese. Methods: The study cohort comprised 6557 adult critically ill patients hospitalized at the Intensive Care Unit of the Ghent University Hospital between 2015 and 2017. Obesity was defined as a body mass index of ≥ 30 kg/m 2. Two causal inference approaches were used to estimate the average effect of obesity in the non-obese (AON): a traditional approach that used regression adjustment for confounding and that assumed missingness completely at random and a robust approach that used machine learning within the targeted maximum likelihood estimation framework along with multiple imputation of missing values under the assumption of missingness at random. 1754 (26.8%) patients were discarded in the traditional approach because of at least one missing value for obesity status or confounders. Results: Obesity was present in 18.9% of patients. The in-hospital mortality was 14.6% in non-obese patients and 13.5% in obese patients. The raw marginal risk difference for in-hospital mortality between obese and non-obese patients was − 1.06% (95% confidence interval (CI) − 3.23 to 1.11%, P = 0.337). The traditional approach resulted in an AON of − 2.48% (95% CI − 4.80 to − 0.15%, P = 0.037), whereas the robust approach yielded an AON of − 0.59% (95% CI − 2.77 to 1.60%, P = 0.599). Conclusions: A causal inference approach that is robust to residual confounding bias due to model misspecification and selection bias due to missing (at random) data mitigates the obesity paradox observed in critically ill patients, whereas a traditional approach results in even more paradoxical findings. The robust approach does not provide evidence that the survival of non-obese critically ill patients would have been improved if they had been obese.

Relationship Between Obesity and Ventilator-Associated Pneumonia

“…The prevalence of obesity is high in the ICU, ranging from 19% to 66% of critically ill patients. 1,2 Obesity seems to be associated with lower mortality in the critically ill patients but increases the risk of complications in several organ systems. 3 Previous studies have suggested a high incidence of community-acquired and health-care-associated infections in obese patients.…”

Body mass index does not impact survival in COVID-19 patients requiring veno-venous extracorporeal membrane oxygenation

“…In some studies, obese patients have been shown to have equivocal, or even improved outcomes compared to non-obese patients, 26 , 27 whereas others have questioned the validity of this observation when appropriate statistical controls were implemented. 28 Whereas obesity places patients at risk for hypertension, diabetes, heart disease, and other disease in the normal population, the reasons why obesity in critically ill patients is associated with lower mortality in the critically ill is not fully understood. 27 , 29 Potential explanations for the obesity paradox in critically ill patients may be related to anti-inflammation, higher energy reserves, greater endotoxin neutralization, increased adrenal steroid synthesis, renin-angiotensin system activation, cardioprotective metabolic effects, and prevention of muscle wasting in the obese.…”

Erfassung und apparatives Monitoring des Ernährungsstatus von Patient*innen auf der Intensiv- und Intermediate Care Station

“…Eine „Dose-Response“-Metaanalyse von 31 Studien mit 238.961 Patient*innen konnte nur bis zu einem BMI ≤ 35 kg/m 2 protektive Wirkungen identifizieren, während ein BMI > 35 kg/m 2 mit einer signifikant erhöhten Letalität einherging [ 17 ]. In einer Studienkohorte von 6357 Patient*innen konnten keine signifikanten Vorteile für kritisch kranke Adipositaspatient*innen (18,9 % der Fälle) identifiziert werden [ 18 ].…”