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Research Snapshot Theater: Sepsis, Adult I

BMI and Mortality in Severe Sepsis: A Retrospective Study at Kaiser Permanente Northern California

Sunday, March 22, 2026
9:45 AM - 10:45 AM Central Time
Location: Connections Central - RST 14
Introduction: Obesity is one of the most common comorbidities in the United States. Despite this, the impact of body mass index (BMI) on mortality in patients with severe sepsis is unclear. The goal of this study is to determine the relationship between BMI and the adjusted 30-day mortality rate in patients with severe sepsis.


Methods: Retrospective analysis was performed on a cohort of adults 18 years and older who presented to the emergency department with suspected infection and was subsequently hospitalized at any hospital in Kaiser Permanente (KP) Northern California between 2012 and 2018. Patients who had lactate >4 mmol/L or < 2 mmol/L, did not receive antibiotics within 6 hours of arrival, required vasopressors within 6 hours of arrival, had comfort-care directives on arrival, were admitted directly to the intensive care unit, were not KP members, or were transferred to multiple hospitals, were excluded from the cohort. The first qualifying visit was included; repeat hospitalizations for the same patient within the study period were excluded. Multivariable logistic regression was used to calculate adjusted odds ratios for adjusted 30-day mortality rates, comparing obese, severely obese, and underweight patients to patients with a normal BMI.


Results: A total of 47,670 patients with severe sepsis were included in the cohort. The mean age was 71.7 years (SD 15.7), 50.8% were male, and the mean BMI was 28.4 (SD 7.7). The overall 30-day mortality rate was 11.24%. The 30-day mortality rate was lower for obese patients (OR: 0.78, 95% CI [0.72, 0.85]) and severely obese patients (OR: 0.62, 95% CI [0.57-0.68]) compared to patients with a normal BMI. The 30-day mortality rate was higher for underweight patients (OR: 1.43, 95% CI [1.28-1.6]) compared to patients with a normal BMI.


Conclusions: In our population of patients with severe sepsis, mortality was lower in obese and severely obese patients when compared to patients with a normal BMI, and mortality was higher in underweight patients when compared to patients with a normal BMI. This is one of the largest cohorts in literature to evaluate the relationship between 30-day mortality and BMI in sepsis.