H/A: Body Composition Measurement (2009)

Citation:
 
Study Design:
Class:
- Click here for explanation of classification scheme.
Quality Rating:
Research Purpose:

Two goals were stated:

  • To determine the magnitude of the relationship between Lean Body Mass (LBM) changes and physical functioning over time in both men and women
  • To determine if changes in LBM or Total Body Weight (TBW) are a better predictor of changes in physical functioning.
Inclusion Criteria:
  • Greater than or equal to 18 years of age
  • All stages of the disease
  • Both genders and minorities.
Exclusion Criteria:
  • Pregnancy at the time of recruitment
  • Severe diarrhea
  • Diabetes, thyroid disease and malignancies except for Kaposi's sarcoma
  • Poor English language fluency.
Description of Study Protocol:

Recruitment

Recruited through advertisements in local newspapers, radio, health clinics and physician networks in Boston, Massachusetts and Providence, Rhode Island.

Design

Nutrition for Healthy Living longitudinal cohort study. Authors stated that study protocol described in detail elsewhere. Patients enrolled had visits every six months in which a survey was administered and blood samples were drawn. The data for this study was collected between April 1995 and June 2000.

Statistical Analysis

  • Used interval between two consecutive visits as the unit of analysis
  • Excluded intervals that were greater than 12 months long or missing key data covariates 
  • The interval approach to capture gains and losses more successfully
  • They used the model of looking at the change in the predictor and the outcome within the same interval
  • SAS version 8.0
  • Descriptive: Means and frequencies reported for all variables for the study intervals and separately for intervals of men and women  
  • Multivariate analysis: Each covariate to determine if they were confounding the relationship between change in physical functioning (PF), Lean Body Mass (LBM) and Total Body Weight (TBW
  • Sensitivity analysis was conducted to determine how the relationship between LBM and TBW to physical functioning might alter the results
  • Cook's distance was used to detect influential points.

 

Data Collection Summary:

Timing of Measurements

Six-month intervals. 

Dependent Variables

Self-reported physical functioning: Measured by four items from a short version of the HIV Patient Assessed Report of Status and Experience. Asked the participants if they had experienced physical limitations in the prior for weeks due to health for vigorous activities (e.g., lifting or strenuous sports), moderate activities (e.g., moving a table, carrying groceries) or daily living activities. The Likert scale categories were: Limited a lot, limited a little or not limited at all. The scale was the mean of the scale items and linearly transformed to a zero-to-100 scale, with zero being worst and 100 being best.

Independent Variables

  • Total body weight measured on electronic scale
  • Lean body mass measured using bioimpedence analysis (BIA). 

 

Description of Actual Data Sample:
  • Initial N: 1,474 (1,165 males, 309 females)
  • Attrition (final N): As above
  • Age: Mean 41.3 years for all, 38.4 years for women, 42.1 years for men.

Ethnicity

  • Total population: 66.3%, White; 22.9%, African American; 6.6%, Hispanic; 4.1% Other
  • Male: 73.1%, White; 16.7%, African American; 5.6%, Hispanic; 4.5%, Other
  • Female: 40.8%, White; 45.8%, African American; 10.7%, Hispanic; 2.6%, Other.

Other Relevant Demographics

  • Income below federal poverty line (percentage):
    • Total, 50.1%  
    • Male, 75.4%  
    • Female, 43.3%
  • Education (percentage):   
    • Less than high school: Total, 11.4%; Male, 8.3%; Female, 23.0%
    • High school: Total, 26.6%; Male, 22.9%; Female, 40.4%
    • More than high school: Total, 62.0%; Male, 68.8%; Female, 36.6%.

Anthropometrics

  • Mean CD4 count: 383±262 cells per µL
  • 10.7% had a HIV viral load of more than 5 log10copies per ml
  • 58.1% were currently using HAART.

Location

Massachusetts and Rhode Island.

Summary of Results:

Changes in Physical Functioning with Lean and Total Body Mass  

Overall change in physical functioning was 1.1 points for male and females combined, with 0.9 points for males and 2.1 points for females.

LBM change was none or 0.0kg for females and 0.1kg for male and for the population as whole 0.1kg.  

There was no significant change for total body weight, neither as group nor for gender.

For males (using multivariate analysis), LBM was significantly related to physical functioning. 

A 5kg-increase in LBM was associated with a 2.2-point (95%  CI 0.9 to 3.4) improvement in physical functioning. However, this same trend was not seen when the sensitivity  analysis excluded intervals of obese patients.  

If excluding those who started the with a PF score of 100, there was a slightly stronger relationship found between LBM and physical functioning.

The greatest improvements in the relationship were seen when excluding CD4 counts more than 200 cells per uL. In this situation, a 5kg increase in LBM was associated with a 4.4 point increase in PF (95% CI 1.1 to 7.8).

A significant relationship was seen with TBW. A 5kg increase in TBM was associated with a 2.6-point improvement  (95%CI 1.3 to 3.9) in physical functioning.

For women, the relationship of change LBM, TBW and change in physical functioning were non-significant. 

  

Author Conclusion:

For men there was a significant relationship between LBM and TBW and physical functioning. A linear relationship was seen. However, in women this relationship was not found. The authors suggest that body composition is not needed and that total body weight is sufficient for predicting physical functioning in males in particular. Also, more sensitive measures of physical functioning and performance are needed to improve the understanding of factors associated with physical performance such as considering interventional studies that evaluate the effects of resistance exercise on women with HIV

Funding Source:
Government: NIDDK and NIH
University/Hospital: Lifespan/Tufts/Brown Center for AIDS Research
Reviewer Comments:

As stated by the authors, there were several limitations to this study. First, the use of self-report techniques for assessing physical functioning may have created bias and inaccurate results. Perhaps using performance testing would have yielded more conclusive results, especially for the gender differences. There was possibility of ceiling effects because when those who began with 100 points were excluded, the relationship for changes in PF were stronger. Performance testing could help limit the ceiling effect. Also, BIA was used and this in itself has limitations in its use to accurately measure LBM in obese vs. non-obese individuals. This could be why more significant changes were seen in the males than the females because the female's BMI rates were greater than the males.

However, despite the limitations, this study does lend itself to adding to the evidence that assessing TBM and LBM in relation to physical function in this population is warranted to include in the management this patient population.

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) N/A
  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? Yes
  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%.) ???
  4.3. Were all enrolled subjects/patients (in the original sample) accounted for? Yes
  4.4. Were reasons for withdrawals similar across groups? ???
  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? ???
  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? No
  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? N/A
  6.5. Were co-interventions (e.g., ancillary treatments, other therapies) described? N/A
  6.6. Were extra or unplanned treatments described? No
  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