Association of Body Mass Index with 28-Day Mortality in Adult Intensive Care Patients with Sepsis: A Retrospective Observational Study

Objectives: The effect of obesity on sepsis outcomes remains controversial. Several studies have described an “obesity paradox,” whereby a higher body mass index (BMI) correlates with improved survival in critically ill patients. This study aimed to investigate the relationship between BMI and 28-day mortality in adult patients with sepsis admitted to the intensive care unit (ICU).
Methods: We conducted a retrospective observational study including 83 adult patients diagnosed with sepsis according to the Sepsis-3 criteria who were admitted to the ICUs of Şişli Hamidiye Etfal Training and Research Hospital between June 2023 and June 2025. BMI was reported using World Health Organization categories and analyzed using three BMI groups based on the final cohort distribution. The primary endpoint was 28-day mortality. Multivariable logistic regression analysis was conducted with adjustment for age, sex, Sequential Organ Failure Assessment score, creatinine, and C-reactive protein.
Results: The median age was 75 years (interquartile range, 66–82), and 55% of the patients were male. Survivors had a higher BMI than non-survivors (27.3 vs. 24.9 kg/m²; p=0.004) and higher albumin levels (p=0.024). BMI was inversely associated with 28-day mortality in the multivariable analysis (odds ratio, 0.74 per 1 kg/m²; 95% confidence interval, 0.58–0.91; p=0.008).
Conclusion: Higher BMI was associated with lower 28-day mortality in septic ICU patients. Further prospective studies are needed to validate this relationship and explore the underlying potential mechanisms.

Keywords: Body mass index, intensive care units, mortality, obesity, sepsis