Association between body mass index change and mortality in critically ill patients: A retrospective observational study

Objective: Previous studies have emphasized the association between baseline body mass index (BMI) and mortality in patients during a stay in the intensive care unit (ICU). However, to our knowledge, few studies have focused on BMI change during an ICU stay. The aim of this study was to explore the prognostic value of BMI change during ICU hospitalization. Methods: This was a multicenter, retrospective cohort study with data extracted from the eICU Collaborative Research Database. Logistic regression models were used to explore the relationship between BMI change and mortality in ICU patients. BMI change was calculated as follows: {[discharge ICU weight (kg) – admission ICU weight (kg)] / height (m)²]}. Interaction and subgroup analyses were conducted for patients grouped with baseline BMI on ICU admission (≥30 versus 25–29.9 versus <25 kg/m²), Acute Physiology and Chronic Health Evaluation (APACHE) IV score (<53 versus ≥53), and ICU length of stay (≥3 versus <3 d). Results: Compared with those with weight loss (n = 17 134), patients with weight gain during ICU hospitalization (n = 17 436) were associated with higher hospital mortality (odds ratio [OR], 1.251; 95% confidence interval [CI], 1.155–1.356; P < 0.001) and ICU mortality (OR, 1.360; 95% CI, 1.227–1.506; P < 0.001) after multivariable adjustment. The associations remained robust in patients with different baseline BMI levels and were especially remarkable among those with higher APACHE IV score and the longer ICU stay. Conclusions: The present study exposed the potential hazard of increasing BMI for hospital and ICU mortalities during ICU hospitalization and indicating that patients in the ICU may benefit from a more balanced nutritional strategy.