The association between waist circumference and body mass index and mortality in obese patients in the ICU

Obesity is a risk factor for various diseases. Effective assessment methods may be helpful to predict survival value, which is still controversial. This study aimed to evaluate the association among waist circumference (WC), body mass index (BMI), and all-cause mortality in critically ill patients. This study included all eligible intensive care unit (ICU) patients admitted to The Second Affiliated Hospital of The Chinese University of Hong Kong (Shenzhen) from January 2022 to December 2023. Demographic characteristics were recorded, and height, weight, and WC were measured and documented for all patients on ICU admission. Baseline data, acute physiology and chronic health evaluation II score, type of admission to the ICU, intensive care unit length of stay, duration of mechanical ventilation (MV), incidence of complications, and mortality were recorded for all patients. Obese patients were categorized based on BMI and WC. In total, 280 patients were included in the study, 61.9% of whom were male. Grouping by BMI showed the highest mortality rate in underweight patients (BMI < 18.5 kg/m2), who also had the longest duration of MV (114.03 hours) and the highest acute physiology and chronic health evaluation II score (16.59 ± 6.74), while the lowest mortality was observed in the normal-weight group (18.5 < BMI < 24 kg/m2). Grouping by WC showed that the central obesity group had an increased mortality rate (23.5%), longer MV time (118.5 hours), longer mean intensive care unit length of stay (7.04 days), and a higher incidence of acute kidney injury (72.1%), with a significant association between WC and mortality. This study suggests that in obese ICU patients, the impact of BMI on mortality is weak, and WC may be a potential and reasonable evaluation tool for predicting the risk of death.