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


Ray DE, Matchett SC, Baker K, Wasser T, and Young MJ. The effect of body mass index on patient outcomes in a medical ICU. Chest 2005; 127:2125-2131.

PubMed ID: 15947330
Study Design:
Prospective Cohort Study
B - Click here for explanation of classification scheme.
Quality Rating:
Positive POSITIVE: See Quality Criteria Checklist below.
Research Purpose:
The purpose of the study was to determine if degree of obesity influenced mortality and complication rate in adult patients admitted to a medical ICU.
Inclusion Criteria:
All patients age 20 or older consecutively admitted to a medical ICU with stays > 24 hours.
Exclusion Criteria:

Patients not admitted to the MICU.

Description of Study Protocol:

Recruitment All patients age 20 or older consecutively admitted to a medical ICU.

Design Prospective cohort study

Blinding used (if applicable) No


Intervention (if applicable) None


Statistical Analysis

Using ANOVA for continuous variables and X2 test for discrete variables, BMI groups were compared by age, APACHE II diagnosis, length of stay in MICU, total length of stay in hospital, mortality, days on mechanical ventilation, and hospital costs. Investigators used logistic regression to examine BMI and mortality. Rates of complications were compared using ANOVA.

Data Collection Summary:

Timing of Measurements

Dependent Variables

  • Length of stay in MICU
  • Length of stay in hospital
  • APACHE II score
  • Need for mechanical ventilation
  • Number of days on ventilator
  • Mortality rate
  • Costs

Independent Variables

Body Mass Index

Control Variables


Description of Actual Data Sample:


Initial N: 2,148 patients (50% male gender)

Attrition (final N): N/A

Age: mean age 63.4 ± 17.9 years with 50% male gender

Ethnicity: not described

Other relevant demographics:

Anthropometrics Groups were stratified into cohorts per World Health Organization categories:

Underweight: (BMI ≤ 18.5) n = 350; mean BMI 17.5

Normal weight: (>BMI 18.5 ≤ 25) n = 663; mean BMI 22.7

Overweight: (BMI 25 to 29.9) n = 585; mean BMI 27.2

Obese: (BMI ≥ 30 to 39.9) n = 396; mean BMI 33.9

Severely obese: (BMI ≥40) n = 154; mean BMI 47.6

Location: Lehigh Valley Hospital, Allentown, PA


Summary of Results:



There were no significant differences between BMI groups in relation to length of stay iin MICU or hospital, APACHE II score, need for or days on mechanical ventilation, mortality rate, or costs.  

Other Findings

 Investigators used Scheffe post hoc analysis and identified severely obese patients as mostly younger and female.

Author Conclusion:
BMI had no effect on outcomes.
Funding Source:
Foundation associated with industry:
Reviewer Comments:
The authors did not describe medical diagnoses. Most of the discussion was only vaguely related to the study. There was a large missing data rate of 23.4% (accounts for neutral study design rating).
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.) 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? 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? Yes
  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? Yes
  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? Yes
  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.) Yes
  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? 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