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Underweight is independently associated with mortality in post-operative and non-operative patients admitted to the
Javier D Finkielman1, Ognjen Gajic, Bekele Afessa
1Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine, Mayo Clinic College of Medicine, Rochester, MN, USA. afessa.bekele@mayo.edu.
Insights
Low body mass index (BMI) is linked to increased intensive care unit (ICU) mortality for all patients. Both low and high BMI increase length of stay in post-operative ICU patients.
Area of Science:
- Critical Care Medicine
- Clinical Epidemiology
- Metabolic Health
Background:
- Body Mass Index (BMI) is a key indicator of body fat.
- Previous studies suggest a link between BMI and mortality post-intensive care unit (ICU) admission.
- The specific impact of BMI on mortality and length of stay (LOS) in ICU patients requires further investigation.
Purpose of the Study:
- To investigate the association between Body Mass Index (BMI) and mortality in intensive care unit (ICU) patients.
- To determine the effect of BMI on the length of stay (LOS) for patients admitted to the ICU.
- To analyze these effects separately for post-operative and non-operative patient groups.
Main Methods:
- Retrospective cohort study utilizing the APACHE III database.
- Inclusion of height and weight data to calculate BMI upon ICU admission.
- Categorization of patients into five BMI subgroups: <18.5, 18.5-24.9, 25-29.9, 30.0-39.9, and >=40.0 Kg/m2.
- Multiple logistic regression analysis to assess the independent impact of BMI on hospital mortality.
- Calculation of ICU length of stay ratio (observed to predicted LOS).
Main Results:
- A low BMI (<18.5 Kg/m2) was significantly associated with increased mortality in both post-operative (OR=2.14) and non-operative (OR=1.51) ICU patients.
- Post-operative patients with obesity (BMI 30.0-39.9 Kg/m2) showed a reduced mortality rate (OR=0.68).
- Post-operative patients with very low BMI (<18.5 Kg/m2) or very high BMI (>/=40.0 Kg/m2) experienced a significantly higher ICU length of stay ratio compared to normal BMI individuals.
Conclusions:
- Low BMI is a significant predictor of increased mortality among both post-operative and non-operative intensive care unit (ICU) patients.
- Both underweight and obese BMI categories are associated with increased length of stay in post-operative ICU patients.
- BMI stratification provides valuable insights into patient outcomes in critical care settings.
Abstract:
BACKGROUND: Low and high body mass index (BMI) have been recently shown to be associated with increased and decreased mortality after ICU admission, respectively. The objective of this study was to determine the impact of BMI on mortality and length of stay in patients admitted to the intensive care unit (ICU). METHODS: In this retrospective cohort study, the Acute Physiology and Chronic Health Evaluation (APACHE) III database of patients admitted to the ICUs of a tertiary academic medical center, from January 1997 to September 2002, was crossed with a Hospital Rule-based Systems database to obtain the height and weight of the patients on admission to the ICU. The cohort was divided in post-operative and non-operative groups. We created the following five subgroups based on the BMI: <18.5, 18.5 to 24.9, 25 to 29.9, 30.0 to 39.9, >/= 40.0 Kg/m2. A multiple logistic regression analysis was used to determine the independent impact of BMI on hospital mortality. The ICU length of stay ratio was defined as the ratio of the observed to the predicted LOS. P-value < 0.05 was considered significant. The 95% confidence interval (CI) was calculated for the odds ratio (OR). RESULTS: BMI was available in 19,669 of the 21,790 patients in the APACHE III database; 11,215 (57%) of the patients were admitted post-operatively. BMI < 18.5 was associated with increased mortality in both post-operative (OR = 2.14, 95% CI, 1.39 to 3.28) and non-operative (OR = 1.51, 95% CI, 1.13 to 2.01) patients. Post-operative patients with a BMI between 30.0 to 39.9 had a lower mortality rate (OR = 0.68, 95% CI, 0.49 to 0.94). Post-operative patients with BMI <18.5 or BMI >/= 40 had an ICU length of stay ratio significantly higher than patients with BMI between 18.5 to 24.9. The addition of BMI < 18.5 did not improve significantly the accuracy of our prognostic model in predicting hospital mortality. CONCLUSIONS: Low BMI is associated with higher mortality in both post- and non-operative patients admitted to the ICU. LOS is increased in post-operative patients with low and high BMIs.
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