FNOA: Assessment of Overweight/Obesity (2012)

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

To determine whether there is a gender difference in how body mass index (BMI) relates to self-reported functional limitations. Also to evaluate whether the method of categorizing BMI changes the observed results.

Inclusion Criteria:

7,120 individuals who:

  • Completed a modified Level II Nutrition Risk Screen between September 1994 and June 1997
  • Were enrolled in a Medicare managed-risk health plan in rural Pennsylvania
  • Had nurse-measured height and weight data.
Exclusion Criteria:

Persons who had a recent weight loss of 10 or more pounds in the previous month while completing the Nutrition Risk Screen between September 1994 and June 1997.

Description of Study Protocol:

Recruitment

Subjects were recruited from a group of elderly living in rural Pennsylvania who completed a modified Level II Nutrition Risk Screen upon enrollment in a health plan.

Design

Cross-sectional analysis of a cohort

Blinding used

Not used 

Intervention

Not applicable 

Statistical Analysis

  • Logistic regression was used to evaluate the relationship between BMI category and functional limitations separately for men and women 
  • Adjusted relative odds ratios and 95% confidence levels of self-reported functional impairment were determined for each BMI category 
  • The analyses were completed using STATA version 5.0 (STAT Corp., College Station, TX). 

 

Data Collection Summary:

Timing of Measurements

Between September 1994 and June 1997

Dependent Variables

Functional limitations were measured by self-reported assessments reported on checklists. The limitations assessed included needing assistance with bathing, dressing, grooming, toileting, eating, preparing or shopping for food, walking or when traveling.

Independent Variables

BMI calculated from heights and weights measured by project nurses or obesity determined by NIH guidelines. 

Control Variables

  • Age
  • Polypharmacy
  • Depression.
Description of Actual Data Sample:
  • Initial N: 7,756 individuals
  • Attrition: 307 men and 329 women were excluded leaving a sample of 7,120 individuals
    • 3,312 men
    • 3,808 women
  • Age: 65-98 years with an average of 71.7±5.7 years
  • Ethnicity>99% were non-Hispanic
  • Other relevant demographics:
  • Anthropometrics: 47.5% of the sample were male and 53.3% were female
  • Location: Rural, central Pennsylvania.
Summary of Results:

Key Findings

  • How BMI relates to self-reported functional limitation depends on both gender and method of categorizing BMI
  • When relative odds ratios were used to report functional limitations by BMI and sex, gender differences were found 
  • When BMI was considered in gender-specific quintiles, women in the highest quintile of BMI had increased risk of functional impairment; there was no relationship between BMI and functional impairment in men 
  • When BMI was categorized by the NIH obesity guidelines, both men and women with BMI >40 had significantly increased risk of functional limitation. 

Other Findings

  • Although functional limitation increases among the obese, the BMI value at which risk increases is lower for women than for men
  • Among men the risk of limitation increases only among those with BMI ≥40; for women risk starts to increase significantly at BMI ≥35.
Author Conclusion:

The mechanisms behind gender discrepancy in self-reported functional limitation remain unclear. Studies may need to consider men and women separately, because how BMI relates to function depends on gender. Further research is needed to evaluate how changes in weight and body composition during middle and old age affect functional status.

Funding Source:
Not-for-profit
Robert Wood Johnson Foundation
Other non-profit:
Reviewer Comments:

Large sample size.

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? ???
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.) 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? 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? 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? ???
  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? ???
  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? 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? N/A
  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