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SCI: Preventing Overweight (2007)

Citation:

Monroe MB, Tataranni PA, Pratley R, Manore MM, Skinner JS, Ravussin E. Lower Daily Energy Expenditure as Measured by a Respiratory Chamber in Subjects with Spinal Cord Injury Compared with Control Subjects. Am J Clin Nutr, 1998; 68: 1223-1227.

PubMed ID: 9846850
 
Study Design:
Case-Control Study
Class:
C - Click here for explanation of classification scheme.
Quality Rating:
Positive POSITIVE: See Quality Criteria Checklist below.
Research Purpose:

To measure 24-hour energy expenditure in SCI subjects by use of a respiratory chamber, and to compare the results with those from age-matched control subjects.

Inclusion Criteria:
  • Two or more years postinjury
  • Classified as complete SCI
  • Able to perform their own transfers and activities of daily living.
Exclusion Criteria:

None specified.

Description of Study Protocol:

Recruitment

  • Not described for SCI group
  • Data from 59 age-matched, healthy, male control subjects from a database of participants in previous studies at the research unit

Design

  • Comparison of components of 24-hr energy expenditure (via a respiratory chamber) of 10 males with SCI and 59 age-matched noninjured male control subjects.

Blinding used (if applicable):  none

Intevention (if applicable): none

Statistical Analysis

Students’ t-test and a general linear model procedure to compare data between case and control group; analysis of covariance to compare 24-hr respiratory quotients of the two groups after adjusting for % body fat and energy balance.

 

Data Collection Summary:

Timing of Measurements

2 days (the second day= 24-hours in the respiratory chamber)

Dependent Variables

   Energy Expenditure Measurements

  • 24-hr energy expenditure (EE) (continuous CO2 production and O2 consumption)
  • Basal metabolic rate (BMR) (ventilated hood system for 21 minutes after an overnight fast)
  • Resting metabolic rate (RMR) (intercept of linear regression between energy expenditure and physical activity)
  • Sleeping metabolic rate (SMR) (average energy expenditure for all 15 min periods when subjects were active <1.5% of time)
  • Spontaneous physical activity (microwave radar sensors)
  • Thermic effect of food (TEF) (calculated over a 15-hr period using method of Schutz et al)
  • 24-hr respiratory quotient
  • Body composition measured by DXA or hydrodensitometry

   Body composition measured by a) dual-exergy X-ray absorptimometry (DXA): nonbone fat-free soft tissue, fat soft tissue, bone mineral content, percent body fat (all SCI and 33 control subjects) or b) hydrodensitometry (26 control subjects)

Independent Variables

  • Weight maintenance diet 24 hr before, and during chamber stay
  • SCI

Control Variables

  • Medications to control involuntary muscle spasms (not taken during 24-hr respiratory chamber day)
Description of Actual Data Sample:

Initial N:

  • Case: 10 male SCI patients.
  • Control: 59 age-matched, healthy male adults.

Attrition (final N): none reported

Age: Mean control, 32; mean SCI, 35-1/2

Ethnicity: not reported

Other relevant demographics: 9 SCI men were paraplegic; 1 had quadriplegia

Anthropometrics:

Variables

SCI

Control

Weight (kg)

89.9 ± 23.6

70.1 ± 17.2

Height (cm)

176.8

179.9

Fat-free mass (kg)

64.1

51.6

Fat mass (kg)

25.8

17.9

% body fat

26

23

Location:

Phoenix respiratory chamber, Clinical Diabetes and Nutrition Section of NIDDK, Phoenix, AZ

Summary of Results:

  

Energy Variable

Control

mean ± SD

SCI

mean ± SD

Statistical Significance, SCI vs control
Energy intake (kcal/24-hr)

2328 ± 319

1832 ± 264

p < 0.001*

24-hr EE (kcal/24 hr)

2375 ± 45

1869 ± 73

p < 0.01

RMR (kcal/24 hr)

2210 ± 317

1755 ± 64

p < 0.01

SMR (kcal/24 hr)

1656 ± 142

1401 ± 226

p < 0.05

Spontaneous physical activity (%/24 hr)

6.5 ± 2.0

4.6 ± 1.9

p < 0.01

TEF (% of energy intake)

15.3 ± 4.4

12.1 ± 2.7

p < 0.05

24-hr Respiratory quotient

0.87 ± 0.03

0.85 ± 0.02

 

 * Significantly different by design because subjects were fed on the basis of body weight.

After adjustment for fat-free mass, fat mass, and age, 24-h EE and SPE were still lower in SCI than in control subjects.

 

 

Author Conclusion:
  • The 24-hour total and resting energy expenditure were significantly lower in SCI than in control subjects. This difference was independent of differences in body composition, and can be explained by the lower levels of spontaneous physical activity and a lower TEF value in SCI subjects.
  • A reduction of sympathetic nervous system (SNS) activity, as a result of SCI, may have contributed to a lower metabolic rate in this population.
Funding Source:
Government: NIH
Reviewer Comments:
  • Small number of case subjects compared with larger number of control subjects, may have certain effects on statistics results.
  • Only included patients who are able to perform ADL, the actual energy expenditure in most of the SCI patients might be lower.
  • A respiratory chamber is not the ideal condition to detect differences between groups, as individuals are restricted to a small area which elicits less free living energy expenditures.
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) No
  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) Yes
 
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? ???
  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? No
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? ???
  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? N/A
  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.) ???
  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? Yes
  6.2. In observational study, were interventions, study settings, and clinicians/provider described? N/A
  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? 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? 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