FNOA: Assessment of Overweight/Obesity (2012)

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

To study the relationship between body composition and self-reported mobility-related disability.

Inclusion Criteria:
  • Inclusion in the Cardiovascular Health Study cohort
  • White race
  • Availability of bioelectrical impedance measurements, body weight and height at baseline
  • Availability of disability data at baseline
  • Availability of disability data at three-year follow-up timeframe.
Exclusion Criteria:
  • Exclusion from the Cardiovascular Health Study cohort
  • Race other than white
  • Missing data at baseline from bioelectrical impedance, weight, height or disability
  • Missing data on disability at three-year follow-up timeframe.
Description of Study Protocol:
  • Recruitment: Recruitment occurred in four communities in the United States: Sacramento County, CA; Allegheny County, PA; Washington County, MD; and Forsyth County, NC. Details on recruitment methods were published in a previous paper and not duplicated here. 
  • Design: Prospective cohort study with cross-sectional analysis reported on baseline data 
  • Blinding used: Implied with measurements 
  • Intervention: None.

Statistical Analysis

  • Cross-sectional analysis: Logistic regression was used to analyze the association of disability at baseline with quintile of fat-free mass (as well as fat mass) after adjustment for age, education, depression, chronic illness, edema, physical activity, recent weight change, smoking, alcohol use and study site.
  • Prospective cohort analysis
    • To investigate the association between body composition and mobility-related disability three years later in life, only persons who did not report any mobility-related disability at baseline and who had completed the disability questionnaire at three-year follow-up were included.
    • Logistic regression was used to analyze the association of disability at the three-year follow-up with quintile of fat-free mass (as well as fat mass) after adjusting for baseline age, education, depression, chronic illness, edema, physical activity, recent weight change, smoking, alcohol use and study site. Incidence of chronic illness during follow-up was also controlled for.
Data Collection Summary:

Timing of Measurements

Measurements were taken during two time periods.

  • At baseline, disability, body composition, physical activity, recent weight loss, education level, smoking, alcohol use, depression, edema and history of chronic illness were measured
  • At three-year follow-up, disability and incidence of chronic illness were measured.

Dependent Variables

Self-reported mobility related disability (interviewer-administered questionnaire on difficulty in performing 17 tasks).

Independent Variables

  • Quintile of fat mass (bioelectrical impedance)
  • Quintile of fat-free mass (bioelectrical impedance).

Potential Confounding Variables

  • Physical activity (questionnaire measuring how often leisure-time activities were performed in the previous two weeks and the average amount of time spent per session)
  • Recent weight loss (weight loss or gain of 4.5kg was ascertained at baseline)
  • Education level (highest grade or year of school completed)
  • Smoking (any participant who reported smoking during the previous 30 days was defined as smoker; all others defined as non-smoker)
  • Alcohol use (number of alcoholic drinks per week measured at baseline)
  • Depression (Radloff's 10-item self-report Center for Epidemiologic Studies-Depression scale)
  • Edema (pitting ankle edema measured during physical exam at baseline)
  • Chronic illness (self-report of physician diagnosed conditions).
Description of Actual Data Sample:
  • Initial N: 4,809 (2,095 men and 2,714 women) for the cross-sectional analysis; 3,274 (1,489 men and 1,785 women) for the cohort analysis
  • Attrition (final N): 4,809 for cross-sectional analysis; 3,274 for cohort analysis
  • Age: Mean age, 72.4±5.4 years at baseline for women (range, 65 to 100 years); 73.4±5.7 years at baseline for men (range, 65 to 95 years)
  • Ethnicity: White
  • Other relevant demographics: 41.4% of women and 48.6% of men completed at least one or more years of vocational school or higher
  • Anthropometrics: Mean body weight at baseline was 66.7±13.3kg for women (range, 33.4kg to 133.2kg); 79.2±12.3kg for men (range, 48.4kg to 143.0kg). Mean BMI at baseline was 26.4±5.0kg/mfor women (range, 14.7 to 48.3) and 26.4±3.7kg/m2 for men (range, 15.6 to 46.2)
  • Location: Four communities in the United States: Sacramento County, CA; Allegheny County, PA; Washington County, MD; Forsyth County, NC.
Summary of Results:

Key Findings

Cross-sectional analysis:

  • Fat mass was positively associated with self-reported mobility-related disability at baseline
  • After adjusting for potential confounders, women and men in the highest quintile of fat mass were 3.04 and 2.77 times more likely, respectively, to be disabled than those in the lowest quintile
  • Fat-free mass was not associated with mobility-related disability in the regression model that also contained fat mass.

Adjusted Odds Ratios for Self-Reported Mobility-Related Disability at Baseline According to Qintile of Body Fat Mass and Quintile of Total-Body Fat-Free Mass

  Women (95% CI) Men (95% CI) Combined (95% CI)
Quintile of Fat Mass 1 (low)
1.0
1.0
1.0
2
1.16 (0.83,1.62)
1.13 (0.72,1.77)
1.17 (0.89,1.53)
3
1.18 (0.84,1.65)
1.63 (1.05,2.52)
1.33 (1.02,1.74)
4
1.21 (0.86,1.70)
1.69 (1.08,2.66)
1.38 (1.05,1.80)
5 (high)
3.04 (2.18,4.25)
2.77 (1.82,4.23)
2.94 (2.27,3.82)
Quintile of Fat-Free Mass 1 (low)
0.79 (0.57,1.08)
0.79 (0.53,1.18)
0.78 (0.61,1.00)
2
0.62 (0.45,0.86)
0.63 (0.41,0.97)
0.62 (0.48,0.80)
3
0.57 (0.41,0.78)
0.85 (0.56,1.28)
0.65 (0.51,0.84)
4
0.71 (0.52,0.98)
0.74 (0.49,1.13)
0.71 (0.56,0.92)
5 (high)
1.0
1.0
1.0

Prospective cohort analysis

  • Men and women in the highest quintile of fat mass at baseline were more likely to become disabled after three years than those in the lowest quintile
  • Persons in the highest quintile of fat mass were more than two times more likely to become disabled than were those in the lowest quintile
  • Persons in the lowest quintile of fat-free mass did not have a higher risk of becoming disabled
  • Low fat-free mass at baseline was associated with a lower risk of being disabled at the three-year follow-up
  • Fat-free mass was not a significant predictor of mobility-related disability in the model that also included fat mass
  • Weight change during the three-year follow-up period was not a significant predictor of mobility-related disability
  • Stratification of the cohort by age (64 to 74 years and at least 75 years), study site or health status did not change the results.

Adjusted Odds Ratios for Self-Reported Mobility-Related Disability at the Three-Year Follow-Up, According to Baseline Quintile of Body Fat Mass and Baseline Quintile of Total Body Fat-Free Mass in Persons Reporting No Disability at the Baseline Examination

  Women (95% CI) Men (95% CI) Combined (95% CI)
Quintile of Fat Mass 1 (low)
1.0
1.0
1.0
2
1.14 (0.73,1.76)
0.96 (0.58,1.58)
1.05 (0.76,1.46)
3
1.37 (0.88,2.12)
0.90 (0.53,1.53)
1.14 (0.82,1.58)
4
2.00 (1.31,3.05)
1.33 (0.80,2.21)
1.67 (1.22,2.31)
5 (high)
2.83 (1.80,4.46)
1.72 (1.03,2.85)
2.22 (1.58,3.10)
Quintile of Fat-Free Mass 1 (low)
0.57 (0.38,0.88)
0.97 (0.58,1.60)
0.70 (0.51,0.97)
2
0.57 (0.38,0.87)
0.81 (0.49,1.35)
0.66 (0.48,0.91)
3
0.55 (0.36,0.83)
0.94 (0.57,1.53)
0.69 (0.50,0.94)
4
0.63 (0.42,0.95)
0.73 (0.43,1.22)
0.68 (0.49,0.93)
5 (high)
1.0
1.0
1.0

 

 

Author Conclusion:
  • The results show that high body fatness is an independent predictor of mobility-related disability in older men and women
  • High body fatness in old age should be avoided, to decrease the risk of disability
  • Persons with high fat-free mass were at higher risk of disability. This finding may be explained by other characteristics of the group.
  • High fat-free mass was associated with high fat mass, indicating that overweight individuals had a higher fat-free mass.
Funding Source:
Government: National Institute on Aging, Epidemiology, Demography and Biometry Program
Reviewer Comments:
  • Longitudinal analysis was only conducted on subjects not reporting a disability at baseline. This sample was leaner (lower percentage of body fat and lower fat mass), younger and more active at baseline than the rest of the cohort.
  • Cohort participants with missing or incomplete data on disability at the three-year follow-up were excluded. Drop-outs were older and tended to be less physically-active at baseline.
  • Follow-up on mobility-related disability was limited to three years. Despite the short timeframe, differences in disability were noted among groups.
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%.) Yes
  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? Yes
  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? 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? ???
  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