Obesity and 1-year outcomes in older Americans with severe sepsis

Abstract

Objectives: Although critical care physicians view obesity as an independent poor prognostic marker, growing evidence suggests that obesity is, instead, associated with improved mortality following ICU admission. However, this prior empirical work may be biased by preferential admission of obese patients to ICUs, and little is known about other patient-centered outcomes following critical illness. We sought to determine whether 1-year mortality, healthcare utilization, and functional outcomes following a severe sepsis hospitalization differ by body mass index.

Design: Observational cohort study.

Setting: U.S. hospitals.

Patients: We analyzed 1,404 severe sepsis hospitalizations (1999-2005) among Medicare beneficiaries enrolled in the nationally representative Health and Retirement Study, of which 597 (42.5%) were normal weight, 473 (33.7%) were overweight, and 334 (23.8%) were obese or severely obese, as assessed at their survey prior to acute illness. Underweight patients were excluded a priori.

Interventions: None.

Measurements and main results: Using Medicare claims, we identified severe sepsis hospitalizations and measured inpatient healthcare facility use and calculated total and itemized Medicare spending in the year following hospital discharge. Using the National Death Index, we determined mortality. We ascertained pre- and postmorbid functional status from survey data. Patients with greater body mass indexes experienced lower 1-year mortality compared with nonobese patients, and there was a dose-response relationship such that obese (odds ratio = 0.59; 95% CI, 0.39-0.88) and severely obese patients (odds ratio = 0.46; 95% CI, 0.26-0.80) had the lowest mortality. Total days in a healthcare facility and Medicare expenditures were greater for obese patients (p < 0.01 for both comparisons), but average daily utilization (p = 0.44) and Medicare spending were similar (p = 0.65) among normal, overweight, and obese survivors. Total function limitations following severe sepsis did not differ by body mass index category (p = 0.64).

Conclusions: Obesity is associated with improved mortality among severe sepsis patients. Due to longer survival, obese sepsis survivors use more healthcare and result in higher Medicare spending in the year following hospitalization. Median daily healthcare utilization was similar across body mass index categories.

Figure 1

Survival of Sepsis Patients by BMI Category

Figure 2. Functional Limitations Before and After Sepsis Hospitalization

Mean number of functional limitations (±SE) as measured by deficiencies in activities and instrumental activities of daily living (I/ADLs) are depicted. There were differences in baseline limitations (p = 0.05), but no differences in newly acquired or total limitations across BMI categories (p = 0.15 and 0.64, respectively).