CI: Body Weight and Outcomes: Mixed ICU Patients (2007)


Goulenok, Cyril, M Monchi, J-D Chiche, J-P Mira, J-F Dhainaut and A Cariou. Influence of overweight on ICU Mortality: a prospective study. Chest 2004;125:1441-1445.  

PubMed ID: 15078757
Study Design:
Retrospective Cohort Study
B - Click here for explanation of classification scheme.
Quality Rating:
Positive POSITIVE: See Quality Criteria Checklist below.
Research Purpose:
To determine if there a relationship between BMI and mortality among ICU patients
Inclusion Criteria:
  • All adult patients hospitalized in the medical ICU from 1/1/1999 to 1/1/2000


Exclusion Criteria:
  • Patients who died or were discharged from ICU within 24 hours
Description of Study Protocol:

Recruitment Chart review of all patients admitted to ICU and stayed >24 hours

Design:  retrospective cohort

Blinding used (if applicable)  n/a

Intervention (if applicable) n/a

Statistical Analysis

Continuous data presented as median and interquartile range; X2 or Fisher exact test for categorical data; used Mann-Whitney test to compare numeric data between groups; performed univariate analysis using nonparametric tests, and variables significantly associated with ICU mortality were entered into a multiple logistic regression model. A two-tailed p value of < 0.05 indicated statistical significance.

Data Collection Summary:

Timing of Measurements n/a

Dependent Variables

  • Length of Stay: measured in days
  • ICU mortality: measured by death
  • Time and duration of mechanical ventilation: measured in days
  • Nosocomial infections: measured as infections occurring > 48 h after admission
  • Invasive procedures performed: urinary or vascular catheter placement, tracheotomy
  • Simplified Acute Physiological Score (SAPS II)

Independent Variables:

  • Body Mass Index (patients considered to be obese if BMI > 27 which corresponded with upper quartile of patient BMIs)



Description of Actual Data Sample:


Initial N: 813 patients (58% male gender)

Attrition (final N): n/a

Age: cohorts significantly different in age (p<0.001) by univariate analysis

  • nonobese mean age 48 (34-65)
  • obese mean age 58 (47-71)

Ethnicity: not described

Other relevant demographics:

  • No significant differences in admission diagnoses, male gender, smoking history, immunodepression, nosocomial infections, mechanical ventilation, or duration of mechanical ventilation.between obese and non obese groups.



Location: Twenty four bed medical ICU unit in a university hospital in France that has approximately 1000 critical care admissions per year.


Summary of Results:
Univariate Analysis


Non obese


p Value


48 (34-65)

58 (47-71)






Length of Stay (d)

3 (2-7)

4 (2-9)


SAPS II predicted mortality (% given as 95% CI)

13% (11-15)

18% (15-260


ICU Mortality (%)




Multivariate Analysis

Variable OR 95% Confidence Interval p value
Age 1.01 0.00 - 1.02 0.098
LOS in ICU 1.02 0.99 - 1.04 0.11
SAPS II (each additional point 1.08 1.07 - 1.10 <0.0001
BMI > 27 1.83 1.10 - 2.86 0.017

Other Findings


Author Conclusion:
Using multivariate analysis, predictive factors for mortality were SAPS II (p < .0001) and BMI > 27 (P < .01).
Funding Source:
University/Hospital: Hopital Cochin Port-Royal Paris, Institut Jacques Cartier (France)
Reviewer Comments:

The authors classified obesity as upper quartile of BMI. This resulted in individuals of BMI > 27 categorized as "obese". This is different from categorization used by NHLBI in the practice guidelines (BMI > 30 obese). Differences in age and severity of illness at admission may be problematic, although the authors did address these differences through multivariate analysis in contribution to mortality.

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) Yes
  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? No
  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? No
  3.3. Were concurrent controls or comparisons used? (Concurrent preferred over historical control or comparison groups.) N/A
  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? No
  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? Yes
  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? Yes
  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? N/A
  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? N/A
  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? N/A
  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