The association between body mass index and ICU 28-day mortality rate in patients with sepsis: A retrospective observational study.

Objectives: Sepsis remains the major cause of mortality among critically ill patients worldwide, indicating the importance of better understanding of its influencing factors for fast recognition and management. Although greater concerns have been raised about the "obesity paradox" and sepsis related mortality, the evidence regarding on overweight or obese septic patients is still controversial. To provide more clinical evidence for the exploration of body mass index (BMI) on sepsis prognostic prediction, we assessed the association of BMI with 28-day mortality of septic patients in intensive care unit (ICU).

Methods: This was a retrospective observational study with patient data extracted from the eICU Collaborative Research Database. We employed a logistic regression to assess the effect of admission BMI levels on sepsis related mortality risk. Furthermore, the two-piecewise linear model was used to identify BMI mortality thresholds, and BMI-outcome associations were evaluated by interaction tests and subgroup analyses.

Results: Our cohort included a total of 17,454 patients, of whom 1555 (8.91 %) died within 28 days after being admitted to the ICU. The connection between BMI and 28-day mortality in the ICU displayed a U-shaped curve. The threshold effect analysis results in two inflection points of BMI were 23.62 kg/m² and 45.53 kg/m². When the BMI was <23.62 kg/m², the mortality rate decreased by 7 % (95 %CI 0.91, 0.96, P<0.0001) for every 1 increment in the BMI. When the BMI was ≥45.53 kg/m², the mortality rate increased by 8 % (95 %CI 1.01,1.15, P = 0.0322) for every 1 increment in the BMI. Subgroup analysis showed that neither age nor sex covariates affected the stability of these results (all P for interaction≥0.05).

Conclusions: In septic ICU patients, the correlation between BMI and 28-day mortality exhibited a U-shaped pattern, indicating that both low and extremely high BMIs were linked to a heightened risk of mortality within 28 days.