CI: Body Weight and Outcomes: Trauma Patients (2007)


Neville AL, Brown CV, Weng J, Demetriades D, Velmahos GC. Obesity is an independent risk factor of mortality in severely injured blunt trauma patients. Arch Surg. 2004 Sep;139(9):983-7.

PubMed ID: 15381617
Study Design:
Retrospective Cohort Study
B - Click here for explanation of classification scheme.
Quality Rating:
Positive POSITIVE: See Quality Criteria Checklist below.
Research Purpose:
The objective of this study was to characterize the relationship between obesity and blunt trauma outcomes.
Inclusion Criteria:

All blunt trauma patients admissions to the surgical intensive care unit at an academic level I trauma center from January 2002 to December 2002.

Exclusion Criteria:

All patients who were not blunt trauma admissions to the surgical intensive care unit at an academic level I trauma center from January 2002 to December 2002.

Description of Study Protocol:


All blunt trauma patient admissions to the surgical intensive care unit at an academic level I trauma center from January 2002 to December 2002.

Design: Retrospective cohort

Blinding used: not applicable

Intervention:  not applicable

 Statistical Analysis:

 Values ae reported as mean±SD, odds ratio, and 95% confidence intervals, or as raw percentages.  Categorical variables were compared using X2 or Fisher exact tests, and continuous variables were analyzed using 2-tailed t test.  Dichotomous variables were created out of continuous variables at clinically significant cut-off points.  These, along with categorical variables, were entered into univariate analysis.  Variables with a difference of P<.20 were included in step-wise logistic regression to identify independent risk factors of mortality.  Statistical significance considered at p<0.05.


Data Collection Summary:

Timing of Measurements

For this retrospective analysis, data on each patient was extracted from both a trauma registry and a computerized SICU database. Admission data was extracted and complications, length of SICU stay, length of hospital stay and mortality was also retrospectively collected.

Dependent Variables

  • mortality
  • complications: included renal failure requiring dialysis, respiratory failure requiring intubation, acute respiratory distress syndrome, pneumonia, sepsis, multiple organ failure (MOF) defined as the failure of 2 or more organ systems, thromboembolic event, wound dehiscence.

Independent Variables

Body Mass Index (BMI) was calculated using the definition of obesity by both the National Institutes of Health and the World Health Organization.  Height and weight for the BMI were obtained on intake to the SICU.  Obese group was defined as having BMI of 30 or higher and the nonobese group BMI of lower than 30.

Control Variables


Description of Actual Data Sample:

Initial N: 242 with 69% male

Attrition (final N): not applicable

Age: Mean (SD) age of 45±21 years

Ethnicity: not given

Other relevant demographics: none given

Anthropometrics 63 (26%) were obese (mean±SD BMI, 35±7), and 179 (74%) nonobese (mean±SD BMI, 24±3) significantly different; p <0.001

Location:  Academic level 1 trauma center at a county referral hospital (Los Angeles)

Summary of Results:

Independent Risk Factors for Mortality
  Adjusted Odds Ratio P
  (95% Confidence Interval) Value
Severe head injury 34.8 (8.9-165.9) <.001
Pulmonary contusion 10.4 (2.9-41.8) <.001
Body Mass Index (> 30) 5.7 (1.9-19.6) .003
Injury Severity Score > 20 4.6 (1.4-17.5) .01
Age > 55 y 1.6 (1.3-2.2) <.001

Obesity was an independent predictor of mortality with an adjusted odds ratio of 5.7 (see above table)

Admission characteristics:  Of the total patients, 63 (26%) were obese (mean±SD BMI, 35±7), and 179 (74%) nonobese (mean±SD BMI, 24±3) significantly different; p <0.001.  Mechanisms of injury and injury patterns were similar between groups.  The obese and nonobese groups were similar with regard to Glasgow Coma Scale score (mean±SD, 11±5 vs 11±5), and injury severity score (mean±SD, 21±13 vs 20±14).

Obese group had a statistically significant higher incidence of multiple organ failure (13% vs 3%; P=0.02).

Obese and nonobese had the same SICU length of stay (mean±SD, 10±9 days vs 11±10 days; P=.65) and overall length of stay (mean±SD, 24±23 days vs 21±17 days; P=.47.

Other Findings


Author Conclusion:

Obesity is an independent predictor of mortality in critically ill patients following severe blunt trauma.

Funding Source:
Reviewer Comments:

Quality Criteria Checklist: Primary Research
Relevance Questions
  1. Would implementing the studied intervention or procedure (if found successful) result in improved outcomes for the patients/clients/population group? (Not Applicable for some epidemiological studies) N/A
  2. Did the authors study an outcome (dependent variable) or topic that the patients/clients/population group would care about? Yes
  3. Is the focus of the intervention or procedure (independent variable) or topic of study a common issue of concern to dieteticspractice? Yes
  4. Is the intervention or procedure feasible? (NA for some epidemiological studies) N/A
Validity Questions
1. Was the research question clearly stated? Yes
  1.1. Was (were) the specific intervention(s) or procedure(s) [independent variable(s)] identified? Yes
  1.2. Was (were) the outcome(s) [dependent variable(s)] clearly indicated? Yes
  1.3. Were the target population and setting specified? Yes
2. Was the selection of study subjects/patients free from bias? Yes
  2.1. Were inclusion/exclusion criteria specified (e.g., risk, point in disease progression, diagnostic or prognosis criteria), and with sufficient detail and without omitting criteria critical to the study? Yes
  2.2. Were criteria applied equally to all study groups? Yes
  2.3. Were health, demographics, and other characteristics of subjects described? Yes
  2.4. Were the subjects/patients a representative sample of the relevant population? Yes
3. Were study groups comparable? Yes
  3.1. Was the method of assigning subjects/patients to groups described and unbiased? (Method of randomization identified if RCT) Yes
  3.2. Were distribution of disease status, prognostic factors, and other factors (e.g., demographics) similar across study groups at baseline? Yes
  3.3. Were concurrent controls or comparisons used? (Concurrent preferred over historical control or comparison groups.) Yes
  3.4. If cohort study or cross-sectional study, were groups comparable on important confounding factors and/or were preexisting differences accounted for by using appropriate adjustments in statistical analysis? Yes
  3.5. If case control study, were potential confounding factors comparable for cases and controls? (If case series or trial with subjects serving as own control, this criterion is not applicable.) N/A
  3.6. If diagnostic test, was there an independent blind comparison with an appropriate reference standard (e.g., "gold standard")? N/A
4. Was method of handling withdrawals described? N/A
  4.1. Were follow-up methods described and the same for all groups? N/A
  4.2. Was the number, characteristics of withdrawals (i.e., dropouts, lost to follow up, attrition rate) and/or response rate (cross-sectional studies) described for each group? (Follow up goal for a strong study is 80%.) N/A
  4.3. Were all enrolled subjects/patients (in the original sample) accounted for? N/A
  4.4. Were reasons for withdrawals similar across groups? N/A
  4.5. If diagnostic test, was decision to perform reference test not dependent on results of test under study? N/A
5. Was blinding used to prevent introduction of bias? N/A
  5.1. In intervention study, were subjects, clinicians/practitioners, and investigators blinded to treatment group, as appropriate? N/A
  5.2. Were data collectors blinded for outcomes assessment? (If outcome is measured using an objective test, such as a lab value, this criterion is assumed to be met.) N/A
  5.3. In cohort study or cross-sectional study, were measurements of outcomes and risk factors blinded? N/A
  5.4. In case control study, was case definition explicit and case ascertainment not influenced by exposure status? N/A
  5.5. In diagnostic study, were test results blinded to patient history and other test results? N/A
6. Were intervention/therapeutic regimens/exposure factor or procedure and any comparison(s) described in detail? Were interveningfactors described? Yes
  6.1. In RCT or other intervention trial, were protocols described for all regimens studied? N/A
  6.2. In observational study, were interventions, study settings, and clinicians/provider described? Yes
  6.3. Was the intensity and duration of the intervention or exposure factor sufficient to produce a meaningful effect? Yes
  6.4. Was the amount of exposure and, if relevant, subject/patient compliance measured? Yes
  6.5. Were co-interventions (e.g., ancillary treatments, other therapies) described? N/A
  6.6. Were extra or unplanned treatments described? N/A
  6.7. Was the information for 6.4, 6.5, and 6.6 assessed the same way for all groups? Yes
  6.8. In diagnostic study, were details of test administration and replication sufficient? N/A
7. Were outcomes clearly defined and the measurements valid and reliable? Yes
  7.1. Were primary and secondary endpoints described and relevant to the question? Yes
  7.2. Were nutrition measures appropriate to question and outcomes of concern? Yes
  7.3. Was the period of follow-up long enough for important outcome(s) to occur? Yes
  7.4. Were the observations and measurements based on standard, valid, and reliable data collection instruments/tests/procedures? Yes
  7.5. Was the measurement of effect at an appropriate level of precision? Yes
  7.6. Were other factors accounted for (measured) that could affect outcomes? Yes
  7.7. Were the measurements conducted consistently across groups? Yes
8. Was the statistical analysis appropriate for the study design and type of outcome indicators? Yes
  8.1. Were statistical analyses adequately described and the results reported appropriately? Yes
  8.2. Were correct statistical tests used and assumptions of test not violated? Yes
  8.3. Were statistics reported with levels of significance and/or confidence intervals? Yes
  8.4. Was "intent to treat" analysis of outcomes done (and as appropriate, was there an analysis of outcomes for those maximally exposed or a dose-response analysis)? N/A
  8.5. Were adequate adjustments made for effects of confounding factors that might have affected the outcomes (e.g., multivariate analyses)? Yes
  8.6. Was clinical significance as well as statistical significance reported? Yes
  8.7. If negative findings, was a power calculation reported to address type 2 error? N/A
9. Are conclusions supported by results with biases and limitations taken into consideration? Yes
  9.1. Is there a discussion of findings? Yes
  9.2. Are biases and study limitations identified and discussed? Yes
10. Is bias due to study's funding or sponsorship unlikely? Yes
  10.1. Were sources of funding and investigators' affiliations described? Yes
  10.2. Was the study free from apparent conflict of interest? Yes