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 between excessive body weight and the onset of functional impairment across time among older adults.

Inclusion Criteria:
  • Enrolled in the Asset and Health Dynamics Among the Oldest Old (AHEAD) survey
  • Completed both the 1995 and 1998 assessments
  • Free of strength impairment during the 1995 assessment
  • Age older than 70 years at the initiation of the cohort in 1993.
Exclusion Criteria:
  • Strength impairment reported during the 1995 assessment
  • Not enrolled in the AHEAD survey.
Description of Study Protocol:

Recruitment

Recruitment for the AHEAD survey was reported elsewhere and not duplicated. 

Design

Prospective cohort design.

Statistical Analysis

Logistic regression was used to estimate the probability of onset of functional impairment in each of the dependent variables (strength, upper body mobility, lower body mobility and activities of daily living). 

Data Collection Summary:

Timing of Measurements

Two surveys from the AHEAD study were used for this analysis. Height, weight, BMI, socioeconomic and demographic data, health behaviors and medical conditions were taken from the 1995 survey. Measurement of functional impairment was taken from the 1998 survey. 

Dependent Variables

  • Strength (assessed with questions about whether respondents have any difficulty sitting for two hours or longer, stooping, kneeling or crouching, getting up from a chair after sitting for long periods of time and pulling or pushing large objects such as a living room chair)
  • Upper body mobility (assessed with questions about whether respondents have difficulty lifting or carrying an object that weighs over 10 pounds, picking up a dime from a table and lifting arms to shoulder level)
  • Lower body mobility (assessed with questions about whether a respondent has difficulty walking several blocks, walking one block and climbing a flight of stairs)
  • Activities of daily living (assessed with questions about whether a respondent has difficulty dressing, bathing, eating or getting out of bed.

Independent Variables

  • Height (self-report)
  • Weight (self-report)
  • BMI (calculated from self-reported height and weight)
  • Socioeconomic and demographic factors
  • Health behaviors (cigarette smoking, binge drinking, exercise)
  • Health status (self-report of physician diagnosed hypertension, diabetes, cancer, lung disease, heart disease, arthritis or stroke).
Description of Actual Data Sample:
  • Initial N: 4,087 (37.8% male)
  • Attrition (final N): N varies for each of the dependent variables based on the number of respondents with completed answers (no missing questions or answer of "I don't do") for each variable.
    • N=1,418 for strength
    • N=2,460 for lower body mobility
    • N=2,554 for upper body mobility
    • N=3,373 activities of daily living
  • Age: Mean age 78.0 during 1995 survey
  • Ethnicity: 90.6% white, 2.7% Latino, 6.7% African American
  • Other relevant demographics:
    • 51.6% married
    • Mean years of education 11.7
    • Mean household income $31,614
  • Anthropometrics: 46.3% normal weight, 2.9% underweight, 37.2% overweight, 13.5% obese
  • Location: United States.
Summary of Results:

Key Findings

  • Respondents who were overweight (OR, 1.48; 95% CI: 1.15 to 1.91) or obese (2.17; 95% CI: 1.32 to 3.56) were more likely to experience the onset of a strength impairment than respondents who are normal weight when controlling for socioeconomic factors, demographic factors, health behaviors and health conditions
  • Respondents who were overweight (OR, 1.48; 95% CI: 1.08 to 2.03) or obese (2.07; 95% CI: 1.31 to 3.27) were more likely to experience the onset of a lower body mobility impairment than respondents who are normal weight when controlling for socioeconomic factors, demographic factors, health behaviors and health conditions
  • Respondents who were obese (1.74; 95% CI: 1.16 to 2.61) were more likely to experience the onset of an ADL impairment than respondents who are normal weight when controlling for socioeconomic factors, demographic factors, health behaviors and health conditions. No significant difference was observed in respondents who were overweight.
  • No significant difference was noted in likelihood of developing an impairment in upper body mobility in respondents who were overweight or obese when compared to normal weight respondents in the model including socioeconomic factors, demographic factors, health behaviors and health conditions. In the model considering only socioeconomic and demographic controls, obese (1.48; 95% CI: 1.07 to 2.05) individuals were more likely than normal weight individuals to develop an impairment in upper body strength.

Other Findings

  • Older adults who do not participate in regular exercise experience the onset of functional impairment in higher proportions across all four functional domains. 55.9% of respondent impaired in strength vs. 46.4% not impaired in strength reported not exercising (P<0.01). 64.6% of respondents impaired in lower body mobility vs. 48.5% not impaired reported not exercising (P<0.001). 68.2% impaired in upper body mobility vs. 51.7% not impaired did not exercise (P<0.01) and 74.1% impaired in ADLs vs. 57.5% not impaired did not exercise (P<0.01).
  • The mean number of serious health conditions reported was also significantly higher in respondent reporting functional impairment across all four domains. In respondents with a strength impairment, 1.4 serious health conditions were reported vs. 0.7 in those without impairment (P<0.001). In respondents with a lower body mobility impairment, 1.6 serious health conditions were reported vs. 1.1 in those without impairment (P<0.001). In respondents with an upper body impairment, 1.9 serious health conditions were reported vs. 1.1 in those without impairment (P<0.001). In respondents with an ADL impairment, 2.4 serious health conditions were reported vs. 1.4 in those without impairment (P<0.01).
Author Conclusion:
  • Using a large, nationally representative sample of older adults, findings show that body weight does have an influence on the onset of functional impairment over time
  • Body weight is not only related to functional impairment among older adults, but it also predicts functional impairment over time
  • Findings show that health behaviors and health conditions do partially explain the relationship between body weight and functional impairment
  • One health behavior that seems to be a particular threat to functional impairment is lack of exercise.
Funding Source:
Government: National Institute on Aging
University/Hospital: Wayne State University
Reviewer Comments:
  • Onset of functional impairment was measured after three years of follow-up, which may or may not be long enough to observe the effect of being overweight or obese on function
  • The respondents of this survey were a relevant sample of the target population of the "oldest old." The mean age was 78 years during the first survey. Any individual with a functional limitation reported on the first survey was excluded from this analysis leaving only functional respondents, at baseline, to participate. One might hypothesize that being overweight or obese would predispose a person to functional limitation at a younger age than 78. This was not investigated. The length of time that the respondent was overweight or obese was also not studied; nor was weight loss or gain. While there still seems to be an effect of overweight and obesity on physical decline over a brief period in the later elderly years, it is important to keep the study design in mind when interpreting the data.
  • Lower levels of education and lower household income were noted in persons who reported the onset of a functional decline, although these factors were controlled for in analysis
  • The sample size for each variable studied varied drastically, largely because the researcher excluded respondents that did not answer one or more questions considered, or the respondent answered, "I don't do." Some examples of questions included were "carrying an object that weighs over 10 pounds," or "pulling or pushing a large object across the living room." 
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? ???
  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.) 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%.) Yes
  4.3. Were all enrolled subjects/patients (in the original sample) accounted for? Yes
  4.4. Were reasons for withdrawals similar across groups? Yes
  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? No
  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.) No
  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? ???
  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? No
  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? No
  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? No
  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? No
  7.6. Were other factors accounted for (measured) that could affect outcomes? No
  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)? Yes
  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