FNOA: Assessment of Overweight/Obesity (2012)

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

To investigate the relationship of total and regional body composition, determined by dual-energy X-ray absorptiometry (DXA), with self-reported physical disability status.

Inclusion Criteria:
  • Participant in the Framingham Heart Study
  • Attended the 22nd clinical examination in 1992 to 1993
  • Agreed to a whole body DXA scan
  • Completed self-reported physical disability status.
Exclusion Criteria:
  • Did not complete a whole-body DXA scan
  • Incomplete or missing data on self-reported physical disability status
  • Did not attend the 22nd clinical examination of the Framingham Heart Study.
Description of Study Protocol:

Recruitment

  • The original Framingham Heart Study cohort was recruited from 1948 to 1951
  • Women and men aged 30 to 62 were asked to participate
  • The current paper is a cross-sectional analysis of a subset of Framingham participants alive in 1992 and 1993, that completed the 22nd biannual clinical examination.

Design

Cross-sectional analysis of cohort data.

Blinding Used

Implied.

Statistical Analysis

  • Reported correlations are Pearson's product-moment correlations
  • The Mantel-Haenzel chi-square statistic was used to test the association of health status, smoking, use of alcohol, estrogen use and physical disability score with tertile of skeletal muscle mass and tertile of percentage body fat
  • ANOVA was used to test the association of tertile of skeletal muscle mass and tertile of percentage body fat with continuous variables
  • Multiple logistic regression analysis was used to assess the association of the categorical disability scores with tertile of skeletal muscle mass after adjustment for age, education, physical activity, health status, smoking, alcohol use, estrogen use and body height. The analysis was repeated with percentage body fat as an additional covariate.
  • Similar analysis was done using tertile of maximum grip strength, tertile of waist circumference, tertile of the ratio of waist and hip circumference as the main independent variables
  • The associations between body composition and the ordinal disability scores were evaluated using analysis of variance. 
Data Collection Summary:

Timing of Measurements

  • Participants completed a questionnaire and physical examination during a clinic visit in 1992 or 1993 (this was the 22nd biannual clinic visit for Framingham participants). Disability status, self-rated health, measurements of grip strength and anthropometric measurements were completed during the clinic visit.
  • Body composition was assessed by DXA within three weeks of the clinic visit if the participant agreed to the scan
  • Physical activity and measures of comorbidity were used from the participant's 20th biannual examination, four years prior to the 22nd exam. Physical activity was not measured on the 22nd examination.
  • The Framingham Heart Study measures chronic disease (comorbidity) on a careful disease-adjudication process for each condition. Data from the 22nd examination was not available for publication in this paper.

Dependent Variables

Self-reported physical disability status was measured using a nine-item scale.

Independent Variables

  • Skeletal muscle mass was measured by DXA
  • Percentage body fat was measured by DXA
  • Maximum grip strength was measured on the dominant hand, using a Jamar isometric dynamometer
  • Waist circumference
  • Ratio of waist and hip circumference.

Control Variables

  • Physical activity
  • Health status
  • Smoking status
  • Alcohol use
  • Estrogen use (women)
  • Education level
  • Recent weight loss.
Description of Actual Data Sample:
  • Initial N: 753 (478 women and 275 men)
  • Attrition (final N): 753
  • Age: 72 to 95 years
  • Ethnicity: Not reported
  • Other relevant demographics: Not reported
  • Anthropometrics: Not reported
  • Location: Framingham, Massachusetts, USA.
Summary of Results:

Key Findings

  • No association was observed between the prevalence of physical disability and total body skeletal muscle mass (P>0.4), nor was an association observed for leg skeletal muscle mass.  After multi-variable adjustment, women and men in the lowest tertile of total body skeletal muscle mass were not more likely to be disabled than those in the highest tertile. Adding percentage body fat as a covariate slightly increased the OR for physical disability (OR, 0.73 for women and 1.33 for men), but the association remained non-significant.
  • The prevalence of physical disability and mobility-related disability in both men and women was positively-associated with percentage body fat (P<0.05). After adjustment for potential confounders, women and men in the highest tertile of body fatness were 2.69 (95% confidence interval, 1.45 to 5.00) and 3.08 (95% confidence internal, 1.22 to 7.81) times, respectively, more likely to be disabled than those in the lowest tertile.
  • The distribution of body fat (measured by waist circumference and the ratio of waist and hip circumference) was not associated with disability
  • Including weight change during the past four years as a covariate did not alter the associations.
Author Conclusion:
  • A high percentage of body fat, not low skeletal muscle mass, is associated with physical disability in both men and women
  • Because it can not be ruled out that persons with low skeletal muscle mass dropped out earlier in the cohort (either by attrition or death), prospective studies are needed to further assess the relationship between body composition and physical disability.
Funding Source:
Government: National Institute on Aging; USDA Human Nutrition Research Center on Aging; National Heart, Lung and Blood Institute
University/Hospital: Harvard Medical School
Reviewer Comments:
  • The generalizability of the findings is limited to healthier older people
  • Disability was self-reported.
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.) Yes
  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%.) 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? N/A
  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? 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? No
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