Background: Obesity is a severe multifactorial disorder that carries high morbidity and mortality. Objectives: This study aimed to evaluate the possible association between body mass index (BMI) and mortality in patients admitted to intensive care units (ICU). Methods: In this cross-sectional study, all patients admitted to the ICU were studied. The demographic characteristics, ICU, and hospital length of stay, organ failure, mortality, duration of mechanical ventilation, the occurrence of nosocomial infection, and type of admission were recorded for all patients. Patients were categorized based on their BMI. Results: In total, 502 patients were studied who 53.2% of them were male. Most of the death (28.6%) were recorded in the obesity class II patients, while the lowest rate (3.9%) was for the normal-weight patients (P value < 0.001). The APACHE II and waist circumference had a statistically significant association with the mortality rate (P value < 0.001). After adjusting for age and gender, a significant association was found between waist circumference and mortality rate (OR = 1.15, 95% CI = 1.03 - 1.29; P value = 0.014), APACHE II score, and mortality rate (OR = 2.79, 95% CI = 1.91 - 4.07, P value < 0.001); but there was no significant association between BMI and mortality rate. Conclusions: This study demonstrated that BMI is associated with an increased risk of mortality, regardless of age and gender. However, after adjusting for age and gender as confounding factors, BMI didn’t have a significant effect on mortality, while the APACHE II score and waist circumference affected the mortality rate.

Background: Obesity, a wide-ranging disorder all around the world, is associated with significant morbidity and mortality in the general population. Regarding the present controversies, this study aims to evaluate the possible association of body mass index (BMI) and mortality in patients admitted to intensive care units.Methods: During this cross-sectional study, all patients admitted to the intensive care unit of two university affiliated hospitals in northwest of Iran from November 2017 to March 2019 were enrolled. The demographic characteristics of patients, length of stay in the intensive care unit and hospital, organ failure, mortality, duration of mechanical ventilation and vasopressor-therapy, type of nutrition, the occurrence of nosocomial infection, type of admission (medical, surgical, trauma) were recorded for all patients. According to the WHO classification of BMI, patients were divided into the six groups, and the data were analyzed accordingly.Results: Of the 502 patients studied, 267 were male (53.2%) and 235 were female (46.8%). The highest mortality rate was observed among the obesity class II patients (35 < BMI < 40) with 28.6%, while the lowest rate was observed in the normal-weight patients (18.5 < BMI < 25) with 3.9%. The highest length of hospital stay was seen in patients with BMI > 30 with 12 days of hospitalizations. APACHE II and waist circumference had a statistically significant relationship with the mortality rate of patients (P-value < 0.001).Conclusion: The current study showed that BMI could be related to mortality, regardless of waist circumference and APACHE II score. However, considering waist circumference and APACHE II score as confounding factors, BMI does not have a significant effect on mortality and only affect the morbidity of patients.